July 12, 2001

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: I have two apple trees that have flowered and produced fruit the four years I have lived in this house. This year is no different; each tree has flowered and is in the process of growing fruit. However one apple tree's bark is turning green. I am not sure what the problem is. I regularly prune the trees in winter, apply bands and have one of those moth attracting tents. (E-mail reference, London, England)

A: Not a problem. It sounds like algae or moss growing on the bark. You folks have quite a bit of rainy, foggy weather conducive to such growth, which is not harmful to the woody plants.

Enjoy your apples.

Q: I have three questions regarding leaves of some of my flowers: My delphinium leaves as well as a few other perennials have a kind of mottled yellow pattern in them. The plants have all been fertilized and the yellowing is a part of the entire leaf ( very light). Another plant showing the same type of mottling is rose mallow (Malva). What should I do to get the leaves healthy?

I would like to keep the iris leaves looking nice this summer. Some are already turning brown at the tips or have brown spots. What should I spray to prevent this? What do I use to prevent hollyhock rust? Last year really devastated the hollyhocks and most leaves died. (E-mail reference)

A: The mottled leaves sound like the "etchings" of a very small insect larvae called the leaf miner. Generally their destruction is only cosmetic and not lethal. No spray is necessary as they have already done their damage and moved on. Some decline in appearance is to be expected in iris once the blooming has passed. You can spray with an all-purpose fungicide like Bordeaux mixture or Daconil 2787, along with a fertilization with Miracle-Gro. Spray your hollyhocks with a fungicide like Daconil 2787 (chlorothalonil) at the first sign of rust development. Avoid splashing water on the foliage, remove all plant debris this fall, keep the area weed-free as much as possible.

Q: You have given a couple suggestions for treatment of black knot disease. One is pruning out the knots and spraying the tree with a lime-sulfur mix. In one place it refers to the timing as a dormant application and another leaves the impression it is during the growing season.

Which method is correct, or are they both acceptable? You also mentioned the use of a product called Cavalier, which is evidently applied during the growing season. (E-mail reference, Billings, Mont.)

A: Glad you asked! I didn't mean to imply that lime-sulfur could be used when the trees were in leaf. It should NOT. That's why Cavalier is suggested at this time. Also, the pruning should take place when the tree is dormant in the early spring, then follow up with the lime-sulfur application.

Q: Inquiring minds need to know! Is it safe to eat wild rhubarb? ( Cando, N.D.)

A: Yes it is, assuming it IS wild rhubarb. Unless you are 100 percent certain, you should stay away from it. Actually, rhubarb is an immigrant, landing on both coasts in the mid-18th century by Europeans and Russian fur traders to Alaska. When I was in Alaska recently I came across a plant that was more than 6' tall and at least as wide! What you are seeing is really an "escape" from cultivation.

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 grew an ornamental or miniature orange tree from a seed from fruit off the parent tree. It is around 5 or 6 years old and has never flowered or borne fruit. It stands about 4 1/2 feet tall and is very healthy. It looks more like a bush then a tree. I understand these trees will bear fruit when they are mature. Approximately how old is that? Should my tree have started to flower? (E-mail reference)

A: The problem is that you have selected a seed, or "pip" as they are sometimes known, from a plant that was bred to bear fruit in the miniature form. It will eventually bear fruit, but it will do so only when it gets large enough. This is the problem with sexual (seed) propagation from a hybrid. To perpetuate the dwarf fruit-bearing size you must take a cutting and root it.

Q: I have a question from my 80-year-old aunt who was born and raised among the pines and now lives in an apartment in Fargo with an enclosed patio. She wishes to overwinter some 1-foot Norway spruce in 1-gallon pots in her patio (not heated, it does freeze). She likes them as a potted semi-indoor plant to bring back the good ol' days. Is it possible? (Fargo, N.D.)

A: In horticulture almost anything is possible. It depends on the willingness of the person to solve the problems. Your aunt needs to insulate the root ball and spray the foliage with Wilt-Pruf before freeze-up in the fall. This may be more work than she is willing to do or have done for her. The bottom, sides, and top need to be wrapped in insulation material completely and moved as close to a heat source–like a window--as possible. If she can keep the sun mostly off the plant, that will help too.

Q: For the last two or three weeks something has been digging up our lawn at night ( I mean MAJOR). We have not seen anything, so we know it is during the night. We have heard Canada geese flying nearby during the day and we are assuming that they are coming in at night digging for grubs or something. The holes are 2-4 inches across and also that deep, plus, of course, mud is thrown around the holes making a very messy looking yard. Do you think that it is geese, and what can we do about it? Do we need to get rid of the worms, and how? ( LaMoure, N.D.)

A: I have never heard of geese being that hard up for food. I would tend to think it might be a skunk, raccoon, or mole. You might try applying a soil insecticide like Sevin in the granular form to kill off the grubs and reduce the earthworm population to see if that brings about an improvement.

Q: I have two large maples that seeded naturally about 30 years ago. I have a problem because they produce huge amounts of seed, which clogs up the eaves troughs of my neighbors to such an extent that some of them are experiencing water problems. I have started getting complaints about this. I like the trees and do not want to have to get rid of them, mainly because of the pleasure they give me, but also because it would be expensive because of their proximity to houses. Is there some type of chemical control I can use, through injection into the bark or by spraying? I know that apple growers can control seed production by such methods. If not, do you have any other solutions? (E-mail reference)

A: No sprays, sorry. But you can tell your neighbors that they can install screening on their gutters to keep the seeds and leaves out. We've done it at my own house. I would never even consider taking a tree down for that reason! Stuff is going to get into gutters unless you live in an open prairie with no trees around. Gutter screen is inexpensive and easy to install.

Q: I'd like to offer another idea for the woman who wrote that her husband dumped left-over minnows on her lawn. You suggested that the fish go to the compost pile. Being an organic gardener for awhile now, I think that may cause some problems. Any time animal products are put in the compost pile it attracts vermin, and lots of maggots! It's pretty much taboo to ever put any meat, even vegetables with some grease on them, in the compost. An alternative would be to dig under the compost and bury the fish in about a foot or more of dirt (my parents saved several trees on our land by burying the leftovers of fish cleanings under ailing trees). By the next year that dirt will be very fertile and ready to use in the garden. (Jamestown, N.D.)

A: I know that but didn't think of it at the time! Thanks for the tip and reminder.

Q: We have planted some sweet potatoes and now something is eating the leaves. would you have any guess on what kind of bug that would do that? (E-mail reference, Morris, Minn.)

A: It could be flea beetles, or even slugs. Look for evidence of some kind--slime trails from slugs; little black bugs at the base of the plant. You can try spraying with Sevin dust to see if that controls the feeding.

Q: My wife has quite a few hollyhocks that are at least 9 feet tall and flowering. They appear to be healthy. Do you cut or prune these? They are starting to droop to the ground. (E-mail reference)

A: Most people will stake them, but pruning certainly will not hurt.

Q: Two of my favorite houseplants have recently started growing pale yellow mold in the soil immediately next to the plant. The first time it happened (to an 8-year-old Dracaena) I figured that it was some kind of freak thing and I did my best to scrape it all away and added new soil. Now my Christmas cactus is doing the same thing. Is this fungus (or whatever it is) dangerous to the plant? How can I get rid of it? How do I avoid getting it again? I have been reading up on houseplants the past year and the advice of the experts is conflicting. One expert will advise that you water a plant until water runs out the bottom and then hold off on watering again for one to four weeks, depending on the time of year. Another expert will advise that you water the plant up to three times a week, obviously giving it smaller doses of water. How can both of these methods work? I like the idea of doing less watering, but it's nearly impossible to water larger houseplants until they drain out the bottom. It was after I tried doing this to my dracenea that I grew the mold. (E-mail reference, Anchorage, Alaska)

A: Experts will tell you what they experience under their conditions, which are often not very well explained. Generally, you should know the approximate volume of the container the plant is growing in put approximately that amount of water in each time you water. This will, of course, result in the water coming out of the bottom of the container since it is filled with soil. But like you, I find this is fine for a small container but a headache for a larger one, so I don't do it, choosing instead to water a couple of times a week (when I think of it) with the same amount of water each time, about half a gallon. And, believe it or not, the plant does beautifully for me under this treatment. So, my "expert" advice? Go back to what you were doing before all the experts confused the issue. The fungus you're seeing growing is a saprophyte, not a parasite, and will not harm your plant. Simply scrape it off or repot.

Q: I have a shrub that I thought was dead when I moved here last fall but now a small portion of the dead branches are leafed out and blooming. Someone told me it is a mock orange. The dead branches are about 10 feet tall. It resembles a lilac bush in shape. The leaves are bright green and the blossoms are beautiful, white with yellow stamens. They remind me of an apple blossom except more cup shaped. The buds are rather round. Does this sound like a mock orange? How can I save it, if it is worth saving? Someone suggested I cut all the branches off about a foot above ground level and see if it will renew itself. Will this work? ( Twin Brooks, S.D.)

A: The suggestion about cutting it back completely was a good one, except you don't want to do it now. Wait until fall when it is dormant, or better, do it early next spring before it leafs out. That way the plant will have maximum energy stored for new growth.

Q: I just bought two apple trees and I'm about ready to plant them. They are the same species, Beacon. Will they pollinate each other or do I have to have two different species? ( Osage, Minn.)

A: Yes, but I wouldn't worry. There are usually enough crabapples or other apples within a quarter mile that will help with the pollination. Beacon is a very good apple to enjoy. I'd certainly keep them both.

Q: I planted several different varieties of petunias along with other flowers in containers this year. Several of the petunias have started drying up and falling over. I think aphids may be the problem, but I have sprayed and it seems to have gotten worse. Any suggestions? The other flowers seem to be fine. (E-mail reference)

A: I doubt it is aphids. Most likely it is a simple root rot that originated with the stock when you purchased it. When you planted them the site was ideal for the development of the pathogen. Be glad it was specific for petunias and not the whole planting.

Q: My Schubert chokecherry is in my very small front yard, where I have removed the grass and planted various perennial groundcovers with a view to avoiding the need to water or use any chemicals. The roots of the tree keep putting up little suckers all over the place. Is there any way to discourage this? Someone told me deep watering will encourage the roots to move downward instead of to the surface, but that is rather contrary to my aim of water conservation. (E-mail reference)

A: I wish I could give you a positive answer, but I cannot. There is no effective way to control the sucker growth from these trees. Spreading plastic or landscape barrier will stop it in that immediate area, but they will only come up farther out in the yard. I would honestly suggest simply removing the tree right now. Even doing that, you can be assured of at least 2 years of sucker growth coming up from the remaining roots.

Do you have a gardening or houseplant question? Write to Hortiscope, Box 5051, NDSU Extension Service, Fargo, ND 58105 or e-mail to Ron Smith at ronsmith@ndsuext.nodak.edu. Note to e-mail correspondents: please identify your location (city and state) for most accurate recommendations.

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Source: Ron Smith, (701) 231-8161, ronsmith@ndsuext.nodak.edu
Editor: Gary Moran, (701) 231-7865, gmoran@ndsuext.nodak.edu