Questions on: Plum

Ron Smith, Horticulturist, NDSU Extension Service


Q: I have a Santa Rosa plum tree. This is the first year it's producing fruit. The fruit is tiny, about the size of a golf ball. It's delicious, but so small! Why is that? Also, the small, ripe fruit is falling off the tree. The other day I saw a squirrel sitting on the fence right next to the tree. I think the squirrels are eating my plums! (Long Beach, Calif.)

A: The small size is likely due to the heavy fruit set. To get larger, but fewer plums, do some hand picking early in the season to lighten the load somewhat. Do this just after the fruit has set. This allows more carbohydrate energy to go into the remaining fruits, which gives you (squirrels, too!) something larger to sink your teeth into.


Q: We have a flowering plum tree that hasn't fully bloomed for five years. Its leaves are sparse and it does not look healthy. We took pictures and a branch from the tree to the local nursery. A worker said the tree did not seem to be affected by insects, but was obviously under a great deal of stress and dying back rather than growing. Do you have any suggestions? (e-mail reference)

A: Here is a short laundry list of what the problem could be. It could be black knot, brown rot, phomopsis canker, plum pockets, shothole disease, stem decay or valsa canker, to name a few. It also could be something environmental that is causing the decline. Send a sample of a branch with the symptoms you describe along with a brief description to the plant diagnostic lab at the land-grant university in your state.


Q: I purchased a pipestone plum tree, but I don't know much about plum trees other than I wanted one. Will this tree bear fruit? I don't know if I have any cross pollinators in my area. I do know that there are apple trees and other various fruit trees nearby, but I am not sure how cross pollination works. (Calgary, Alberta)

A: Chances are there are pollinators in your area. Generally, anything within a quarter mile will be effective as a pollinator. Plums will produce without cross pollination, but will be more productive if one is nearby.


Q: I live in central Pennsylvania and have a thundercloud plum tree. The tree was planted two years ago and flowered wonderfully last year. Last summer I noticed some of the branches did not have leaves on them, so I cut them off. I occasionally fertilized the tree last summer with a basic 10-20-20 mix. I also know that the tree was hit hard by Japanese beetles before I noticed and started spraying. This year, the tree barely flowered and the top 1 to 2 feet of every branch did not grow leaves. Is there anything I should do or look for to explain why no leaves are growing on the top of the tree? Thanks for any help you can give me. (e-mail reference)

A: The possible explanation based on what you have told me could be that the tree was planted too deeply. The top of the rootball should be even with the surrounding soil, not deeper. Many folks plant trees too deeply, with the thought that doing so will keep the tree from being blown over. This effectively disrupts the air/moisture balance in the root system, causing the dieback in the canopy of the tree that you described.


Q: My wife and I just got a small, purple plum tree. Her grandmother had it growing in her yard. Our grandmother passed away, so we decided to bring the plum tree to our house. The roots are long, so I want to cut them back some and replant. Is this OK? I was going to plant it today, but my shovel broke. We put it in a bucket of water until I get home from work tomorrow. Please help us because neither of us has a green thumb. (e-mail reference)

A: The more of a root system you can leave on a tree, the better the chance for it to establish successfully.


Q: We planted a thundercloud plum, but a few days later we had a freeze. All of the leaves are wilted and appear dead. What should we do? (e-mail reference)

A: Wait, which is all you or anyone else can do! The tree eventually will come out of this because Mother Nature provides backup buds for leafing-out after irrational weather.


Q: I have a Satsuma plum tree and have purchased a Santa Rosa tree to pollinate it with. It was a bare-root tree, so they don't want to send it home with me until May 10. My other tree is blooming now and I can't find a pollinator around to clip a branch from. The tree has more than 200 blossoms and I don't want to lose this fruit. Do you have any ideas? Also, I have three wild plum volunteers. They have beautiful blossoms every year, but no fruit. What could be the reason? (e-mail reference)

A: Why are they waiting until May 10 to give it to you? What is wrong with planting a bare-root tree? It is done all the time, so that line of thinking just doesn't make sense to me. Where is it you live? What good is a pollinator if it arrives more than two weeks after the cultivar is finished blooming? Unless there is a pollinator nearby and a lot of bee activity, you are out of luck. With your wild plums, lack of fruit set could be due to windy, rainy or cold conditions. It also could be a lack of bee activity at the time the pollen is viable. If these wild plums are self-sterile and from the same parent, they won't set fruit.


Q: Your column is very informative and helpful. I purchased a purple leaf plum in February. The tree has bloomed with flowers and leaves, but about a third of the branches do not have any growth. Does this mean that those branches are dead or is there something I can do? Can this tree be saved? Can I prune off the dead branches? If so, when should I do it? (e-mail reference)

A: Those branches probably are dead. As for the rest of the tree, if it is healthy, there is no reason why you should lose it. The tree may have a weird shape for now, but if it is something you can put up with and train, your tree should be OK. You can prune off the dead branches. With dead material, the sooner it is removed, the better.


Q: I live in Austin, Texas, and have an ornamental, purple-leaf plum. It gets full afternoon sun and morning shade. My problem is that I noticed it is oozing brown sap that forms a big bubble on the bark. The bubbles are on the base of the main trunk. I busted one open and found a jellylike substance inside. (e-mail reference)

A: That oozing usually is a good sign of borer activity. Once started, they are extremely difficult to control. Judging from the location you described, the tree likely will be girdled soon, which probably will kill it.


Q: I have a Newport plum tree that I planted about nine years ago. It has been an easy tree to care for and provides shade and beauty to my yard. However, I have been reading that plum trees planted near sidewalks can cause damage to the sidewalk. Mine is not near a sidewalk, but it was planted 10 to 15 feet from my septic tank. Could the roots of my plum tree damage my septic tank? If I have to remove it, I'll want to replace it with another shade tree. Are there any trees that have root systems that would not run deep enough to damage a septic tank and would be hardy enough for the hot summers and cold winters of the mid-Washington state area? I appreciate any help that you may give. (e-mail reference)

A: Septic tank seepage is a temptation for any tree's root system. Poplars, silver maples and willows are the worst. I suggest that you contact the county Extension agent to see if there is a horticulturist or forester who can help you make a selection that would be the least of the evils for your region of the country. You also could have a root barrier installed between your tree and the septic system. That might be the least expensive and best alternative for you.


Q: A friend of mine has asked me to cut down a wild plum. However, the tree is healthy, full and decorative, which is everything one wants in a tree. However, when he planted the tree he was unaware that it grows as a thicket, so now the suckers have spread to the neighbor’s yard, making it difficult for the neighbor to mow. I have an aversion to cutting such a tree. I also am concerned that with a strong root system; cutting the tree will just make the suckers grow even more. (e-mail reference)

A: You probably are not going to like my answer. Plum and cherry trees are noted for their suckering in most Midwest landscapes. This is something that is not taken into consideration when people go to a nursery or garden center and fall in love with the red-foliaged forms that are on the market. As the years pass, the roots begin sending up suckers throughout its root system. The suckers make it difficult to mow and are unsightly to an otherwise attractive landscape.

You are correct in stating that there will be even more suckering when the tree is cut down, but then everyone affected can go about killing the sucker growth with herbicide applications. If it only affected his property, then he is under no obligation to remove the tree unless he wants to. However, since it impacts a neighboring property, he really has no choice. He should be alerted to the increase in suckering and what to do about it after the tree is removed. The neighbor also should be told and assisted with getting rid of the suckers. Mature trees, such as elms, oaks and giant sequoias, are worth attempting to save because of their longevity, grace, beauty and historical significance. Wild plums are not worth it. I had a suckering experience with a couple of edible plum trees on my property years ago. Between the neighbor’s complaining and my young daughter hurting her foot stepping on a cut-off stump, I was moved to get them cut down. I replaced them with some apple trees. I haven't regretted it one bit.


Q: I purchased a home that has a large plum tree with a trunk diameter of about 30 inches. Last year, it was covered with small, juicy, delicious plums. This year it hardly had any plums and has a large amount of sticky sap leaking out of it. A large branch appeared to die, so now half the tree looks dead and the sap still is leaking. Can it be saved or should it be cut down? (e-mail reference)

A: The tree sounds like it is on the way out. I would suggest cutting it down for two reasons.

The fact that you had heavy-bearing fruit last year is one reason. Your description of oozing sap from some of the branches is an indication that borers have found this tree and are feasting on its last days is the other reason.


Q: We had to cut down a purple plum tree. It never rooted properly and always leaned to the side, so a recent storm knocked it over. Someone at a nursery said we would destroy too much root system trying to replant the tree, so we cut it down. We have a wood-burning fireplace in our home, so we would like to know if this wood is safe to burn inside. (e-mail reference)

A: No problem, as long as the fireplace is properly vented.


Q: We have a plum tree that has some healthy and ripening plums. However, some of the plums have small, cream-colored spots of varying sizes that are rotting. Some of them have a colorless gel on them. (e-mail reference)

A: Dispose of those that are showing the symptoms you describe. Pick up all dropped fruit and dispose of it. Spray the tree next spring, before new growth emerges, with dormant oil. At blossom drop, spray with an insecticide, such as Sevin.


Q: Is it a good idea to fertilize tomatoes as they set fruit or will it result in more foliage? The plants are huge and look healthy. Also, my neighbor has a plum tree that is sending up many shoots in my yard. If I spray them, will it damage her tree? If not, what should I use? They are a real nuisance! Thanks for your advice. I enjoy your column and find it helpful. (Fargo, N.D.)

A: Regular fertilization with a balanced fertilizer, such as Miracle-Gro, will improve growth and fruit set. As long as they are not showing any signs of deficiency and are setting fruit to your satisfaction, don't worry or fertilize. As for the plum suckers, cut them back and then spray with Sucker Stopper RTU. This will stop the suckering. I took my plum trees down years ago because of the continual suckering problem. Thanks for the nice comments about the column!


Q: Three-fourths of the top of my plum tree is dead, so I cut all the dead material off and rounded it on May 21. It looks like fall is here and my wife can't stand to look at it all summer. Will the tree come back or will I have to replace it? (e-mail reference)

A: You haven't been married too long, have you? When your wife is not happy, do something immediately and apologize for having to be told that she isn't happy with a situation. In other words, replace the tree, but probably not with another plum tree!


Q: I will be moving into a new house in May. Can I move my plum tree without destroying it or should I leave it and plant a new tree? The tree is two years old. (e-mail reference)

A: You can move it or plant a new tree, but it is always best to leave a tree in a location where it is doing well instead of moving it to a location that may be in question. Since you have not invested a great deal of time, money and loving care in the tree, it would be better for you to purchase a tree for your new location.


Q: We have five Victoria plum trees in our orchard. They have produced fruit each year, but this year, in the very ripe plums, there is a pale, pink grub inside. The underripe plums seem fine (but still not sure we should eat them). We have chickens in the orchard, so any treatment would have to be OK for them. When we bought the house three years ago, there was a white ring around the trunk of each tree. What is the white ring? (e-mail reference)

A: The best thing you can do is harvest the plums and pick up those that fell off the tree. Destroy those that have the plum curculio grub inside. Sanitation is important in grub control, so do a good job of cleaning up the area this fall. Next spring, before the tree leafs out, spray the tree with dormant oil. The white ring was probably whitewash to protect the tender bark from sunscald during winter the months.


Q: Five years ago I planted about 75 native plum trees in a tree row. They are doing very well. They bloomed the last two years, but haven’t produced any fruit. Is there a reason for this? (Minot, N.D.)

A: It could be that it was too windy at the time the pollen was mature, too rainy, cold or a lack of pollinators. That about covers the ballpark of reasons!


Q: I have a plum tree that has been doing great since we planted it two years ago. The problem is squirrels or birds (I haven’t seen the culprits) are eating the fruit as soon as it starts to get soft. Do you have any suggestions? (e-mail reference)

A: Most likely, the problem is caused by birds. Squirrels steal the produce lock, stock and barrel! You can use a few “tricks” to solve the problem. Throw some bird netting over the tree after the fruit is set, but be sure to secure it to the trunk or else the birds will go up inside the net and get stuck there. Apparently they are not smart enough to figure out how to get back out. Another trick is to hang some owl balloons and aluminum foil around the tree. Finally, a motion sensor sprinkler that can be situated around or in the tree may do the trick. Just remember to turn it off before you approach the tree or you will be doused!


Q: I’m new at growing fruit trees, so I have a lot of learning to do. I have Italian and Stanley plum trees. My problem is I can’t get any fruit off these trees. They won’t produce blossoms. The Stanley is at least 5 to 6 years old. The Italian is 4 to 5 years old. All I gave them for fertilizer last year was a fertilizer stake per tree. This spring, I sprinkled some compost around the base of the trees. (e-mail reference)

A: The trees probably got their flower buds nipped by the cold in the dead of winter or by the warming/freezing cycles in spring. Don’t waste your money on fertilizer spikes because they will not get your tree to flower or help it grow. Most fruit trees do not need fertilization unless you are growing them for commercial purposes or they are growing on nearly pure sand.


Q: I had a wonderful plum tree. I used to eat the fruit off the tree and throw the seeds in the bushes. Out of sight, out of mind. Unfortunately, the tree died from, I suspect, a disease. However, guess what came out of the bushes? I have 10 healthy plum trees, but they do not bear fruit. Can I get fruit from these trees? (e-mail reference)

A: Yes, but you need to be patient. They should start bearing fruit at year five or six.


Q: How can I start a plum tree? Can I start it by seed or grafting? (e-mail reference)

A: Seed is much easier and you get better results. Collect the pits from the plums and sow them this fall after the first hard frost, to a depth of about 4 inches. Winter stratification and moisture should crack the pit coat and most of the seeds should germinate After they are a year old, transplant them the following spring to their permanent location. Squirrels will be the biggest problem because they find the seeds and dig them up. Cover the seeds with hardware cloth until emergence.


Q: Over the last three to four weeks, the leaves on my plum tree have started to turn yellow with some faint green color remaining. Normally they are a very deep, dark green and have red veins. The leaves are still attached to the branches, but are wilting at the stem. I don’t see anything abnormal on the trunk or branches, such as cankers or other damage. It is planted in a fairly shady location (direct sunlight varies, but probably about three to four hours a day) and is surrounded by large trees and a lilac hedge. Also, it is planted about 3 feet from the stump of a flowering crab tree. It is mulched with wood chips. Could it be lacking iron after all the recent rains or possibly from the decomposition of the crab tree? I have started giving it some Miracle-Gro every few days. Does it need chelated iron? (e-mail reference)

A: The tree is in bad shape. Applying Miracle-Gro or chelated iron will not cure what the problem appears to be, verticillium wilt. Cut into one of the branches and look for streaking just under the bark. If there is no streaking, then the problem is armillaria root rot. I don’t know where you live, but it is a problem in many areas of the country because of the heavy rains this season. In judging the environment the tree is planted in, it appears that there is some shade, which will not help the tree. All I can suggest is to back off on the watering and fertilizer and allow things to dry to determine if the tree will recover next year.


Q: Three years ago, my wife and I bought a home that had two small plum trees of some type. The first two years they grew a few plums that were absolutely delicious. This year they were covered with blossoms and have grown considerably. We hope that our loving care has had something to do with it. Despite all the blossoms, the trees barely produced a dozen plums. Is there something in particular we need to know about getting our plum trees to produce fruit? (e-mail reference)

A: If you provide too much loving care in the form of nitrogenous fertilizers, you will get a lot of growth and few plums. To get the tree more productive next spring, drive a sharp-edged spade into the ground just outside the drip line of the tree to cut some of the roots. This usually shocks the plant into reproduction.


Q: I had a lady call about her fruit trees. We are under a frost warning for tonight and she is wondering if there is anything she can do to protect her plum tree. It has small fruit on it. Also, I had a question concerning tomatoes and potatoes. The tops froze off of the tomatoes, but the bottoms seem okay. The potatoes were in blossom and the tops froze. (Dickinson, N.D.)

A: The tree should be ok, and the tomatoes and potatoes should come out of the frost damage with minimal to no consequences. Just have the clients cut the damaged tops back to prevent secondary infections from setting in.


Q: I have a plum tree in my yard that is bearing plums for the first time, but every plum has a worm in it. Is there anything I can do to get rid of the worms now or stop them next year? (e-mail reference)

A: Pick off all the plums with worm infestation and destroy them. Clean up all litter this fall. Next spring; spray the tree with lime-sulfur and then dormant oil before the leaves come out. Spray again with Sevin when the leaves begin coming out and again 10 days later, but do so only when the bees are not active.


Q: We have a thundercloud flowering plum. We were told it doesn’t bear fruit, but ours is. Is it true the plums are poisonous? (e-mail reference)

A: Flowering plum cultivars do bear small fruit. The seeds, leaves and bark are poisonous. Of course, the exception is the fruit we eat. You will be fine if you steer clear of the poisonous parts.


Q: I recently purchased some plum trees, but one of them has a strange problem. On the sprouting twigs and leaf stems, there are occasional little red nodules about the size of a straight pin head. They look like small, but fat (quite protruding) blisters under the skin of the plant. The nodules ooze a small amount of clear liquid, which the ants like to drink. I sprinkled some diazinon around the tree. The ants are now gone, but the blisters are still there. I dug at one of the blisters with a fingernail and they are quite firm. What do you think I should do? (e-mail reference)

A: From your observations, it does not appear to be a borer working its way through the tree. It could be some physical damage from shipping, hail or a bird pecking into the bark. The ants were after the carbohydrate rich exudate emerging from the nodules. My advice is to keep monitoring the tree to be sure that none of the nodules turn out to be borer or bark beetle activity.


Q: I have a problem with my plum tree. When the fruit gets to the size of small grapes, some turn blue as though they were ripening. They then rot and fall off. I suspect a small insect is laying eggs on or in them. What can I do to reduce this damage? Also, deer think that I plant beets solely for their use. I’ve heard that a hot pepper solution sprayed on the leaves curbs their appetite. Do you have a recipe for this solution or some other thoughts on the subject? (Nome, N.D.)

A: To prevent insect activity on your plum tree, you need to spray with an insecticide such as Sevin when bees are not present. Do so at full bloom and about seven days later. You can prepare your own pepper spray, but it is safer (I'm not kidding!) to purchase some RTU material. If they can tolerate that kind of burn, let them have it!


Q: My wife bought a plum last year, which was so delicious that I saved the pit. It's been drying on a window sill for three months. Is it dry enough? Since it's almost winter, should I just let it sit on the sill until spring? Should I plant it indoors or outdoors now? Do you have any specific planting instructions such as soil type, depth or exposure? (Rosemount, Minn.)

A: Plant it outside now. The pit needs to go through the winter in order to germinate. Let's hope it does so you can enjoy a whole tree full of the plums in a few years! Plant it about four inches deep.


Q: My husband and I recently purchased a pipestone plum tree. We only purchased one tree so we are wondering about pollination. We do have what we believe are wild plum trees in our tree row. Our new plum tree is planted just to the south of this tree row. Will these pollinate each other? The wild plum trees have produced very little fruit the last two years. Could the introduction of a different plum tree help with the production of fruit on the wild plums? Are wild plum trees common in my area? (Lake Park, Minn.)

A: The wild plums should provide ample pollen for your recently planted tree. Generally it takes two or three years for the trees to begin to bear fruit. It is common for tree rows to have some wild plums growing in them.


Q: Hope you can help. I have put in some native plum and apple but the tubex is significantly longer than the bare root stock. Should I cut them back to the length of the tree or leave them? (Sheyenne, N.D.)

A: Cut them back to the length of the tree.


Q: I want to move some 3- to 5-foot trees into my yard from where they are growing along a shelter belt. I would intermix them in a line of plum trees. Can I just move them by taking a spadefull of dirt with the root and setting it where I want? (Sheyenne, N.D.)

A: I don't see any reason why not, as long as they are still dormant, and you water them in well. Be sure to plant them at the same depth.


Q: I have a weeping willow tree and two purple leaf plum trees that I would love to get more trees from. I don’t know how or even what it is called but I sure hope it could be done. I just would love to start some new trees from my existing ones. (E-mail reference)

A: Willow trees are very easy to propagate. Simply take some branches about pencil size or larger, about 9 to 12 inches long, and insert them into a sandy loam mixture, keeping them moist until a substantial root system develops. Purple leaf plums are not going to be quite as easy. Take cuttings in early June and try rooting them in the same media but under a mist system. If you can, get some rooting hormone powder and dip the cuttings into it before sticking. If these fail, don't fret; many before you have tried and failed. If fruit is available, remove the hard outer husk and plant this fall where you want them to grow.


Q: My 92-year-old uncle has a question about a wild plum tree that grows behind his house on a bank of the Cannonball River in New England, N.D. In early September my husband and I picked a bumper crop of beautiful plums from this tree. Why does this tree only set fruit every 10 years? My uncle says that the last time he harvested fruit from the tree was about that long ago. The tree flowers every year. (Mandan, N.D.)

A: Fruit set on a particular fruit tree species is sometimes difficult. Many factors have to come together for pollination/fertilization to be successful. Maturation of pollen when the pistil is receptive; action of pollinating insects; lack of wind, rain, or cold weather, and certainly carbohydrate energy to actually produce the fruits. Often it depends on whether or not a cross-pollinator is close by and in bloom sequence and sexual maturity with the desired fruit tree. So, you can see that a lot has to be right for fruit set to be successful.


Q: Is there a spray available that you can use so plum trees don't bear fruit? The plums are making a real mess in my yard. (E-mail reference)

A: A material called "Fruit Stop" contains an ethylene-producing substance that, with the exact right timing, would cause embryo abortion of the fruit, never giving it a chance to form. It’s available in many garden centers. My experience has been that its performance is very undependable.


Q: I recently planted a non-fruit flowering plum tree. In the beginning I had a problem with the watering level but soon the tree started growing leaves instead of losing them. Also, I just recently planted some mini roses in my backyard that were not flowering brightly and prematurely dying. I purchased rose food and thought it can't hurt to put some around the tree. But can it? Now my plum tree leaves are almost transparent, have a green hue to them, and are falling off. Am I killing my tree or is this the work of some disease?

A: The tree doesn't know the difference. What is good for the rose will not hurt the tree.

It sounds more like a disease. I don't know which one it would be. I suggest taking one to your local county extension office for analysis.


Q: I have a plum pit. How do I grow a tree from it? I am a CPA, not a horticulturist, so please help! (E-mail reference)

A: The easiest way is to plant the pit about 2 or 3 inches deep where you want the tree to grow. It will go through winter stratification and scarification and, if the seed is viable, it will germinate and grow into the tree of your plum-producing dreams! Just make sure you plant it in an area where it can grow into a tree, with plenty of sunlight.


Q: What is causing my plum tree to drop its fruit prematurely? My pear tree isn’t dropping its fruit but only has four pears. Is there any fertilizer that I could give to the tree? Am I having problems with it because it is a semi-dwarf pear? I also had a problem with my beets this year. They didn’t produce any roots; what is lacking in my soil? The leaves on my grapes are turning yellow. Is it still safe to eat them? (Bonney Lake, Wash.)

A: Fruit drop can occur for several reasons: drought followed by a period of heavy rain or irrigation.; insect (plum curello) larvae feeding on developing fruit; colder than normal temperatures after a warm period; excessive wind or too heavy a fruit load for the tree to support. Topdressing with barnyard manure is an acceptable way of supplying nutrients. The semi-dwarf nature of your tree has nothing to do with the problems you cite. Generally lack of development of bulbous roots like beets is an indication of low phosphorous levels. I suggest having your soil tested. It will be safe to eat your grapes provided the fruit itself is not infected.


Q: I am sending you some leaves from my plum tree. I would like to know what is on them. It is all over my tree. What do I do, spray or cut the tree down? (Mercer, N.D.)

A: Those are harmless galls; they are nothing to worry about. Spray the tree with dormant oil and lime sulfur next spring just before leaves open.


Q: We need some direction in making a flowering plum turn into a tree vs. a bush. It was planted this spring and is now about 3 feet tall. We know it needs to be pruned to help it get into "tree mode." It has lots of new branches, the lower ones having green leaves. Our concern is to when to start pruning, now as the new branches appear or when it's dormant? How should any area cut be covered, putty or tape? (E-mail reference)

A: The best time to prune is during spring dormancy. It is not recommended to cover the pruning cuts with anything. They will compartmentalize and seal themselves much better without any covering.


Q: We have a single plum tree given to us by a friend. It bears lots and lots of fruit, but almost all the fruit splits and falls to the ground before it ripens. Is there anything I can do to keep the fruit from splitting? Is it possible I'm over-watering? The tree gets hit by the lawn sprinklers every day.

A: Unless you live in the Arizona, New Mexico, Texas, or California desert, you don't need to have the lawn sprinklers come on every day, and having any tree watered each day is certainly detrimental to it's well-being. Without knowing anything else about the tree setting, I would say that the watering cycle is what is causing the fruit splits. I suggest you get the sprinklers either re-directed or replaced. An established, fruit-bearing tree should not need any more than a once a week watering at most, and certainly should be able to grow and produce satisfactorily on much less than that. Reprogram the sprinkler controller to reflect the water needs of your turf. Again, unless under the extreme conditions, most cool-season lawn grasses will remain green on 1 inch of water per week, assuming other proper cultural practices like mowing and fertilization. This translates to 640 gallons per 1,000 square feet of turf. I would suggest applying water as fast as your soil can allow it to infiltrate without runoff, making sure to wet the soil/root zone profile completely, doing so just twice a week or possibly three times under severe conditions and a nearly pure sand soil.


Q: I am interested in starting a few plum trees. My friend has some lovely trees and I would like to take some starts from her tree, but I don't really know how to do it successfully. Any and all help that you can give me will be gratefully accepted. (E-mail reference)

A: You apparently are one who likes challenges. Rooting cuttings is out, as researchers have only had a 7 percent success rate under ideal conditions, so seed is the only way to go. Take seed (remove the pulp) and plant it where you want the trees to grow this fall. I suggest planting several seed to assure something coming up the following spring. First, place the seed in the crisper of your refrigerator in contact with moistened sphagnum peat moss for about 90 days. This is known as stratification. Check periodically to see if the seed has begun to split and the radicle (embryonic root) has begun emergence. If so, plant immediately. But either way, plant before freeze-up this fall. Stratifying it in the coolness of your icebox prior to planting may save you a whole year, otherwise, it has been known to take up to two years for germination to take place when directly sown outdoors without the cold stratification.


Q: I have two semi-dwarf plum trees in my front yard. They are both about 6 feet tall and have been there about two years. In the last few months, they have both been shooting sprouts up into my lawn. These shoots appear mostly within about an 18-inch radius from the trunk. Why does this happen, and is there something I can do to stop it from happening? I'd like to keep them but I don't want them to destroy my lawn or work their way into my plumbing system. (E-mail reference, Pacifica, Cal.)

A: Unfortunately those sprouts coming up from the roots are a big disadvantage of plum trees. You can try placing landscape fabric around the base of the tree to see if that discourages them, but often they come up farther out in the lawn. I had a couple of plums in my back yard that did just that, and when they started sprouting in my neighbors’ yard with them asking me what I was going to do about it. I cut them both down, even though they were both good producers. I fought sprouts from the root system for three years after that!


Q: I noticed my plum trees have some fruit that is twice the size of normal . These fruit are hollow but appear to be alive, that is not in a fungus or mold type of growth. I have attached some photos. (Cavalier, N.D.)

A: The plums have a fungal disease known as "plum pockets" which cause the overgrowth that was evident in your photo. The best management approach is in the spring before new growth begins. Remove all mummified fruit remaining on the tree and pick up all fruit on the ground around the tree. Spray lime sulfur or Bordeaux mixture before new growth begins in the spring. Just make sure the temperature is below freezing at that time.


Q: I have three flowering plum trees (Prunus autumnalis) that bloomed this spring and now the leaves are curling, drying up and falling off. The leaves seem to have dark spots on them also. I could see no bugs or cankers. Would this problem be fatal to the trees and what can we do about it? (E-mail reference)

A: It sounds like it could be brown rot, a fungus that overwinters in the dried or mummified fruit remaining on the tree. Spray with Benomyl or Captan and pick off all old remaining fruit this fall. Spray next spring before leaf out with lime-sulfur spray to sanitize the tree.


Q: My plum trees are infected by something that causes tiny green tubes to form on the bottom of the leaves. What can I do? (Sioux Falls, S.D.)

A: Not to worry. They are likely galls formed from insect or mite feeding or egg laying activity earlier in the season. If you pick one of them apart, you may see a small white or tan grub inside. They cause no serious harm to the tree, just aesthetics, and it isn't worth trying to spray for.


Q: I have an ornamental purple leaf plum tree (P.cerasifera 'atropurpurea' ) that was planted in 1998. For some reason, only the center main trunk still puts out branches with purple leaves. Lower on the trunk are lots of branches with green leaves, and all suckers have green leaves too. Is there anything I can do to encourage more purple leaves? (E-mail reference)

A: That simply means that the graft for the purple leaf character is not dominant enough to suppress bud break, or growth, below it. I encourage you to prune the lower green growth out when it is apparent, and hope the scion wood can become dominant enough to keep the sucker and unwanted growth in check.


Q: We are planning to plant plum trees this spring and are wondering if the Pipestone and Toka are the most hardy varieties for zone 3 on the Minnesota - Canadian border. Or are there other varieties which are both hardy and produce well? (E-mail reference, Baudette, M.inn.)

A: Those are a couple of good ones to use. They produced well for me in my backyard.


Q: Should I spray my fruit trees with any kind of spray at this time? They are plum, apple, cherry, apricot etc. Also I have an apple tree with yellow delicious apples, but lost the name of the tree. Is there any way to identify it and what would you need to identify it? (Hague, N.D., e-mail)

A: All the spraying is done in the early spring or late winter, prior to leaf-out. I suggest a lime-sulfur and dormant-oil spray at that time--these take care of most overwintering insects and diseases.

If you have an apple tree with yellow delicious apples on it, then that is the name of the tree. I do not try to identify apples any longer. It turns out to be too much of a good guess or worse, a shot in the dark!


Q: We have a plum tree that has six main branches; three lost their leaves early and now those branches are weeping, the other branches still have leaves. Any ideas? (e-mail)

A: The plum tree branches could be suffering from either borer damage, with the "weeping" coming from the holes created by the borer activity, or it could be coming from a canker that has developed on the branches. Check on the weeping branches to see if the material is coming out from small holes about the size of pencil lead, or from oozing wounds caused by the fungal canker. In either case, you are likely to lose the tree and are better off to have it removed either this winter or early next spring.


Q: We have a plum tree where the fruit begins to grow then all of a sudden the fruit puffs up and falls off. What is the problem? We also have two apple trees that leafed out nicely, but now the leaves are shriveling up. We dusted with Sevin, but they are still sick looking. (Drake, N.D.)

A: The problem with the fruit on the plum is a fungal disease known as "plum pockets." Apply lime-sulfur in the fall after leaf drop or in the spring just before the buds break open.

The apple trees likely have a disease known as apple scab. Rake up all fallen leaves in the fall and spray next season with Captan or benomyl.


Q: We have one Canada red cherry and two plum trees. How do we watch for black knot? We have never heard of it. (Horace, ND., e-mail) 

A: Be thankful you have never heard of it! If it should ever get started on your trees, you will know it by the following characteristics:

1. Soft greenish growth about this time of year that completely or partially girdles the branches of the tree. These galls develop into black, corky growths that resemble burnt marsh-mallows on a stick.

2. The branches where this gall appears will be either stunted and partially foliated, or completely dead.

3. The disease is a fungus that spreads and is especially active during wet weather in the spring. It has been a good year for the fungus!

Control is by selectively pruning out the infected branches during the fall and late winter. Be sure to cut at least 4 to 6 inches below the area of swelling on the branch. Spray the trees with a fungicide containing benomyl next spring before bud break. Respray two more times at 10-day intervals.


Q: I am having trouble with worms inside my plums when they ripen. There is no evidence of entrance, so I am assuming they lay their eggs in the blossom. Is there something I can spray the trees with at blossom time that is not toxic to my honey bees? (Hague, N.D., e-mail)

A: You are most likely seeing the grub stage of a beetle known as the plum curculio. They lay their eggs in the developing fruit, leaving a small, corky, crescent-shaped wound. The adults for the 1999 season are in the pupal stage in the ground litter and fallen fruit that is around the tree right now. A good spring cleanup would go a long way in reducing their population. 

A spray schedule would be when the fruit has just set and the temperature affects their activity. Around 70 F brings the beetles out, and they begin their feeding and egg laying. The best key for spraying is just about when all the flower petals have fallen. The bees would be finished then, and the beetles would just be getting started. Materials to use are either Sevin or diazinon. Repeat again in about 10 days.


Q: When should I trim my wild plum trees, grape vines and cranberry trees? I also have sandy soil and I am wondering how I can get a nice lawn. I also would like to know what I can do to get larger apples on my tree? (Park Rapids, Minn.)

A: All of the above would be pruned in early spring before new growth emerges. Refer to the enclosed extension publication, "You Can Have a Beautiful Lawn" (H244) to answer your next question, and to get larger apples, do some picking in early June to thin them out somewhat.


Q: For the last two years my wild plum tree has been producing an airfilled fruit-like growth. I see it's happening this year too. Very few real plums are on. What can I do to stop this? (Leola, S.D.)

A: Your plum is likely manifesting a fungal disease known as "plum pockets" (Taphrina species).There is also a chance it is caused by chokecherry midge. Check the fruit to see if any maggot activity is present. My bet goes with the plum pocket fungus.  

This disease is relatively easy to control with good sanitation and by spraying with lime sulfur when the trees are dormant in the early spring or late fall. Be sure the buds havenot yet swollen (spring), and spray to cover tree completely. Be sure to pick up fallen fruit and any remaining on the tree before new growth begins.


Q. Your column is very helpful.

Will Manchurian apricot pollinate a Moongold apricot? Is Manchurian apricot sort of like a wild plum? I mean real common.

Will a wild plum pollinate Underwood plum? I had Pipestone plum and fruit from it and did not have a pollinator. I suppose it lived 15 years. Some wild plum around.

Can you tell me anything about summer cypress or standing cypress? A friend gave seed and in her yard it looks easy to grow but I have trouble starting it. I have found it listed in a 1962 House and Garden bulletin from the Department of Ag—only identified, but I was glad for that identification.

Do you need to thin daffodils? If so, how often? Mine have lots of shoots for which I am happy, but I sure want to keep them doing well. Thanks. (Pierre, S.D.)

A. Thank you for the nice comments about the column. 

The answers are "yes" to your first two questions.

The summer cypress is Kochia scoparia, and also has the common name of burning bush because of its blazing fall color. Seeds need to be soaked for 24 hours, then germinated at 70 F. It is one of the toughest, most heat-tolerant annuals on earth. Makes a nice temporary hedge.

Yes, daffodils can be thinned every three to five years.


Q. I enjoy your column very much.

Could you please help me with this problem? I have a Superior and a Waneta plum tree. This year some of the plums had what looked like a brown weevil forming in the pit and   working its way to the outside. How do I deal with this so it doesn't happen next year?

Thank you. (Tioga, N.D.)

A. The only thing I can think of is the plum curculio. It damages the fruit from egg laying punctures, larval feeding within the fruits and the fall feeding of adult beetles.  

Controls are directed toward sanitation and mechanical measures.

Clean up all fallen fruit this fall, spray with dormant oil early next spring before leaf-out. Then spray the trees with Malathion when the leaves are half open. Discourage any weed  growth around the tree and prune to open the crown to allow predatory birds access to any beetles.


Q. Wild plums have come up under our 50-year-old evergreens. The plants are about 10 inches high and many. What can we spray with? Thanks. (Hillsboro, N.D.) 

A. Those wild plums are most likely suckers arising from the roots of nearby trees. I suggest carefully spraying with Roundup for control. I am afraid that this will be an ongoing chore for you.


Q.Can you tell me why my apricot, peach and apricot-plum cross trees died? They leaf out in the middle of summer and the leaves start to dry up and the trees die. The trees were three to five years old. (Dante, S.D.)

A.There were no visible symptoms on the samples you sent. I suspect girdling by rabbits or voles over the winter, or a crown or root rot. Do you have a gardening or houseplant question? Write to Hortiscope, Box 5051, NDSU Extension Service, Fargo, ND 58105.


Q. I enjoy your column and hope you can help. The enclosed fruit is from a tree that came up voluntarily in my flower garden. What is it? The tree started as a very straight stem with sharp prongs. It has white blossoms in the spring. It is about three or four years old. The fruit comes on, then turns brown and withers. It is a conversation piece to all who stop by. Some clusters have six fruit. I have repeatedly trimmed it.  Thank you. (Turton, S.D.)

A. You sent me the mummified fruit from a wild plum tree that is infected with the disease known as "Plum Pockets," Taphrina pruni. This is a disease that is easily controlled by a single fungicide spray--either in the autumn after leaffall or early spring before bud break. The most commonly used fungicides are Bordeaux mixture, followed by Ferbam.


Q: Perhaps you can help me then. I have a plum tree problem where many of the leaves, particularly the new ones, are curled and wrinkled up (though still green). There are also similar leaves that are brown and dry, apparently the same problem in its latter stages. Any Ideas? (Sunland, Calif., e-mail)

A: From your description of the leaf damage, it sounds like a fungal disease known as plum pockets (Tapheina pruni). You didn't say anything about the fruit being swollen, which is a more obvious symptom, so I suspect that my diagnosis could be incorrect. You may want to try some control applications of approved fungicides like Bordeaux mixture or Ferbam. They both are broad-spectrum fungicides that should take care of the problem.


Q: I would like to know why our apricot tree drops the apricots and our plum trees drop the plums? We are also noticing that our apple tree does the same. (Bismarck, N.D.)

A: So-called June fruit drop is a normal phenomena. The tree is simply shedding the excess, smaller fruit so that more energy can be put into developing the remaining fruit to maturity. Nothing to worry about or do.


Q: When we moved into a 30-year-old house in 1998, we were very pleasantly surprised to see the sickly tree in the backyard bear beautiful, delicious Italian plums. Last summer the tree did not bear fruit (probably due to a killing frost) but this year is another bountiful one. An entire half of the plum tree broke off earlier this year, possibly due to rot. The other half is bearing fruit on schedule but the weight of the plums is so great that the fruit-laden branches have bent to the ground. Some branches have cracked but seem to have enough moisture and sap to still nourish the fruit. Clearly, this poor little tree has been badly hurt. We are utterly ignorant city folk who can't keep houseplants alive. Can this plum tree be saved? What should we do? (E-mail reference, Longmont, Colo.)

A: The plum tree can be saved -- for a short time, likely. First thing I suggest is to brace the branches that are under load stress with either clothes poles or cotton clothes line. Next spring, I suggest contacting a local nursery or greenhouse and see if they would be willing to root some cuttings for you, to replace this tree when it finally caves in. Then prune the tree while still dormant to help support the weight load better. Generally, when fruit trees bear heavier than normal it is a sign of impending death, or a struggle against it. As you harvest this summer, selectively save some of the seed and plant them in an appropriate location before the soil freezes. With luck, you may get something coming up next spring.


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