August 21, 2003

Hortiscope

Ronald C. Smith, Horticulturist
NDSU Extension Service

Q: I've just purchased a house that included a beautiful full red maple in the back yard. I do not know how old this tree is but I noticed a powdery substance on the leaves. Some leaves turned brown and curled. Can I save it or is it doomed? What do I use to spray it with if the tree is taller than my house? (E-mail reference)

A: You don't want to attempt to spray the tree or do a self diagnosis. Make contact with an International Society of Arboriculture Certified Arborist to have the tree inspected and sprayed with the appropriate legal material.

Q: I recently acquired a sick jade plant. The trunk was bent and it had very few leaves. I repotted it, watered it, and put it in morning sunshine. New growth followed and I was thrilled to see it had become so healthy. A couple of weeks ago, it started losing leaves. There have been no changes in its location or my care and there are no signs of disease or bugs. Could it be due to overcrowding of new growth? Since it grew branches in all directions, they have become slightly crowded. Some leaves are resting on each other. Some leaves turned silver and shriveled while others fell off even though they were healthy and green. It now loses about 3 10 leaves a day. I'm hoping the plant is trying to become space efficient in capturing light but I'm afraid it might be something serious. Is this common? (E-mail reference)

A: Try some selective pruning to provide more space for the branches and foliage. It's possible it doesn't need as much water as you were initially giving it after your "rescue."

Q: I planted 500 Rocky Mountain junipers this spring and have found a weed on them I cannot identify. It is like a vine and has elongated heart shaped leaves. When weeding, it seems the root system is almost like a vine underground as well. I've been cultivating between the rows then tilling between the plants and finally hand weeding around the trees. Is there a weed killer available to take care of the problem? (E-mail reference)

A: The weed sounds like creeping jenny, or in some circles, better known as field bindweed.

The best approach is to paint the leaves carefully with Roundup avoiding, as much as possible, getting any on the juniper foliage. This will take persistence on your part, as the root system is quite extensive and will take several re applications to kill it off. Try your best to keep it from going to seed.

Q: This past week you had a question about suckers growing on a crab apple tree. You recommended using a product called "Sucker Stopper." Would this product be effective on sucker roots growing in a Canadian red cherry tree? We have two different types of tree suckers. It has plain sucker roots and suckers on the trunk and branches of the tree. (Fargo, N.D.)

A: Sucker Stopper is supposed to work on both. I have not tried it although I've been told it works on chokecherry tree suckers. Time will tell.

Q: In my yard I have a variegated dogwood that is dying. The branches range from dead to healthy. Some branches have leaves that are turning brown while other leaves are very healthy. It resembles fireblight in apple where the bark tends to be reddish in color and shriveled up like an overdone summer sausage. I'm trimming out all the dead branches. (Mott, N.D.)

A: Unfortunately for all dogwood species, they play host to a plethora of disease organisms but fortunately fireblight is not one of them. If there is no evidence of sawdust around the base of the plant, then I would say, fairly safely, that your problem does not involve borer or stem girdler insects. My best guess is that the plant is suffering from one of the many stem cankers, probably downy mildew. You are correct in removing completely the stems that are showing symptoms. I would suggest adding a spray program to control the spread. Two fungicides come to mind, Banner (propiconazole) and Daconil 2787 (chlorothalonil). The first is a systemic that needs application only 14 or so days, especially in the beginning of the season. The later is a contact fungicide that should be applied weekly. I must emphasize that fungicide is effective at preventative control, not curative. Any applications you make this late in the summer will not have much of an effect but would be most useful next spring, assuming your plant makes it that far. The variegated form of dogwood shrubs are especially susceptible to stem cankers and leaf anthracnose. They all start out looking good as young plants but seem to spiral downward with age.

Q: I have a couple of rose plants that I need to transplant. When is the best time of year to move them? I have a spot in front of my house (south side) that had black plastic put down. On top they have a red rock that I think is scoria. The plastic is real old and is tearing and decomposing. I have a lot of weeds. I would like to cement some of it and then redo the flowerbed. Would you recommend putting plastic down again and then the decorative rocks or just use soil? I do not like to do a lot of weeding. I think I already hurt two of the other roses. I trimmed the branches so now they grow tall but do not produce roses. (Bismarck, N.D.)

A: Spring transplanting is best while they are still dormant. If you are a gambler, you can do it in the fall but I wouldn't do it in our climate. Forget the plastic and rock, use Preen instead and cover with organic mulch. The roses will be a lot happier and so will you!

Q: I have some cattail slough land in South Dakota that is bordered by several expansive and very dense cottonwood groves. These naturally occurring groves have trees that are about 15 feet high so they are fairly young. Should I thin out the groves so that I will have some mature cottonwoods that are spread out at a more desirable spacing? (E-mail reference)

A: Positively! Go for it and good luck.

Q: When our lake lot on Golden Lake in Steele county was leveled and excavated, we opted to keep a few of the dominant trees, which are mostly cottonwoods, at the waters edge. That meant that we had to leave a good deal of sand in that area, basically trying not to disturb the root systems of the trees. I have tried to grow perennials/annuals but haven't been satisfied with the growth of anything, except sedum. I have two Russian sage plants, planted three summers ago, which reached an all time high this summer of around 4 inches! I dug away large areas of sand and filled with good soil from our farm but the water runs off or soaks down through the soil. The soil is always dry even with the excessive rainfall we've had this summer. My husband thinks I need to build up the area by a foot or so and perhaps put a layer of plastic between the sand and new soil. Because of all the tree roots, it's not possible to remove all the sand. I think his idea sounds stupid but I guess I'll try anything. Planting all succulents in that area is a last resort for me. (Portland, N.D.)

A: The best cure for water retention is organic mulch. That way there is a balance of water and air in the root zone that will support plant growth. I suggest incorporating generous amounts of sphagnum peat moss into the soil, planting, then topdressing it with shredded bark mulch. That is a much more ecologically sound approach.

Q: My mother bought me a calla lily for Mother's Day. It was beautiful but the leaves started turning yellow so I repotted it. The leaves have curled up and turned yellow. I thought maybe I was watering too much but not watering as much made it worse. I have also noticed the leaves no longer drip water. (E-mail reference)

A: The plant is trying hard to go into a dormant or rest state. You need to help it by withholding water. Allow it to dry down for about six weeks by barely watering it. After that period, begin watering as you normally would and it should perk up nicely and start to flower.

Q: Our peas got covered with a white-powdered substance about half way through the season. I'm guessing it is powdery mildew. We grow green arrow peas, which we prefer, because of their larger size and yield. What options are available to control this problem? (Mylo, N.D.)

A: A number of options are open. Don't plant peas in the same location every year. Don't save seed from the previous year's crop, instead use clean seed purchased commercially. Select mildew resistant varieties. Improve air circulation and sunlight penetration via selective pruning. Use fungicidal soap that is available commercially.

Q: I know someone who wants to make jam out of black nightshade growing in his garden. Would you recommend it? Do you have a recipe? I understand these were used for jam by our Grandparents and early settlers. (Bottineau, N.D.)

A: I do not recommend it for a number of reasons. I am not going to recommend anything that is growing wild and is a member of a genus (Solanum) that contains many species that are poisonous. Misidentification is always a possibility. The poison in the fruit depends on the degree of ripeness at the point of harvest. They need to be very ripe and well-cooked. Misinterpretation of ripeness and cooking time is again a possibility. Different people have different reactions to these plants. Some can tolerate the alkaloids that are present, others cannot. Why find out the hard way by being taken to the emergency room at the local hospital? There isn't a "need" to do so because we are not in a famine so why take a chance with something marginal? There are plenty of other crops coming into maturity now that make excellent jams.

Q: I found a salamander in my basement. When I was in high school a teacher poured salt on a salamander and said that it would run to the area where it came in or an area that was wet. I am thinking about doing this if I find another one. (E-mail reference)

A: Interesting. I have never heard of that before. Let me know if it works. Thanks!

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: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.nodak.edu