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Hortiscope

Ron Smith answers reader's questions about the world of plants and gardening.

By Ron Smith, Horticulturist

NDSU Extension Service

Q: My peony did not bloom this year and the plant is small. I think it is because I cut the plant down too early in the fall. Will it flower and come back next year? (e-mail reference)

A: As far as plant performance goes, I can't guarantee anything because I don't know the environment it is in, the kind of care it receives or how it was planted. One of the last maintenance procedures performed in the yard in the fall is to remove the foliage from peonies after a few hard frosts, but not sooner.

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 am trying to turn a weed-infested area into a wildflower savanna. I had the dead material from last year, plus some of the topsoil, removed in May. I then tilled, hoping to cut up some of the underground runners to impede regrowth of the nettles, raspberries and poison ivy. I waited two weeks to see what would pop up. Some of each grew back, plus a lot of thistle. I sprayed Brush-B-Gon on the weeds and most are wilting. I want the poison to work through the weed roots and kill some of the runners so the weeds won't grow back as heavily. What should I do next? I've considered pulling up the wilting weeds and putting them in the trash, then retilling and spreading the wildflower seed mix. Should I till and then wait for more weeds to sprout and spray again? I know I never can get rid of all the weeds, but I'm hoping that the native wildflower and grasses will be able to compete with the unwanted weeds. When will the soil be free of chemicals? I've also thought about bringing in a load of black dirt, then spreading the wildflower seeds on fresh soil. Any advice would be great! (e-mail reference)

A: The one thing you did to make matters worse was to rototill the lot. Breaking up the rhizomes of the thistle and quackgrass is one of the best ways of propagating them! I would suggest tilling everything again to see what sprouts. Spray everything that does with Roundup. Grade and sow the wildflower seed. It will germinate this summer and be beautiful for you next year. Expect to have weeds invading the mixture, but, if you stay on top of it, the weeds won't take over. Plants, such as sow and Canada thistle, will work their way back in, but with spot spraying and hand pulling early on, it won't have a chance to establish a colony.

Q: I live in the Pacific Northwest and have fairly sandy soil. I just planted two drummondi maples. I want them to be successful, so what would you recommend for fertilizer? (e-mail reference)

A: Very little, if any, fertilizer. Do a 10-10-10 broadcast around the drip line of the tree every spring.

Q: Can you tell me how to get starts off a mock orange bush? I can't find any information on this. My mother got a start off her sister's bush more than 40 years ago. I've broken pieces off and tried to root them in water, but that didn't work. (e-mail reference)

A: With asexual propagation, timing is important in many cases. Mock orange will root if softwood cuttings are taken at this time of year. The cuttings should be treated with a rooting powder or liquid and stuck in a sand/peat media. The cuttings should be in partial shade and kept moist.

Q: I'm hoping you will take the time to give me some advice on selecting between emerald green arborvitae and juniper skyrocket shrubs. I live in a suburb of Boston and would like to line my driveway with an arborvitae or other decorative shrub. Emerald green arborvitae seems to fit the bill, but juniper skyrocket grows tall and is nice and thin. The reason for the thin choice is so we can see through the shrubs and detect any oncoming traffic when exiting the driveway. We're looking at a possible eight to 10 plants. The emerald green is affordable, but the skyrocket is a little out of price range. Are there benefits to spending the extra money for the skyrocket? Which shrub is easier to prune? (Boston, Mass.)

A: Thanks for a no-brainer! The skyrocket wins hands down. It only gets about 2 to 2.5 feet wide, is moderate in growth, has no particular soil requirements, is tough as nails and is hardy to zone 3. Taking nothing away from the beauty of emerald green arborvitae, it just wouldn't be the best choice for your location.

Q: For Arbor Day this year, we purchased two white oak trees from the city. We planted them about two months ago, but they have not sprouted a single leaf. The branches are flexible and do not break off when we test them. Are the trees still in shock or did they not survive the transplant? (e-mail reference)

A: Scrap the bark off some of the branches with your thumbnail to see if the cambial tissue is green underneath. If it is, there is a slight chance the trees will break bud. If what is underneath is any other color, they are finished.

Q: I'm writing from western Massachusetts. I have a birch tree in my yard that is a couple of years old. I just noticed that quite a few leaves are stripped on the youngest branches. Upon closer inspection, I saw many little, green-striped worms crowded together on the outer leaves. I'm certain they were not there several days ago. It is disgusting! How can I get rid of them? They eat the leaves so quickly. I'm afraid the tree will be pathetic looking within a week. (e-mail reference)

A: This sounds like some type of sawfly species. By this time, they probably are gone, but left behind a damaged tree. The tree should recover and releaf for you in a week or two. I would suggest that you invest in a product called Bayer Advanced Tree and Shrub Insect Control. It will control any subsequent generations of this pest for this year and early next year. It is available at most local garden centers or national chains selling garden products.

Q: I have a variegated maple planted in my yard. We have had the tree for 10 to 12 years. About four years ago, it started getting a few solid green branches mixed in with the variegated ones. This year, three-fourths of the tree is solid green. We are losing the variegation. What can we do? I've noticed that others are having the same problem. Can we help our tree? (Mayer, Minn.)

A: The tree will be OK, but it will not have the variegated foliage in the future. Many times these ornamental anomalies are periclinal chimeras that can revert back to their original form or leaf coloration. Not much can be done about this except to watch it take place and appreciate the diversity of Mother Nature!

Q: One of my weeping pussy willow trees looks like it has some sort of blight. The leaves are shriveling and drying up as if the tree is not getting enough water. Is there any salvation for this tree? When it was planted, this was a very healthy specimen and plenty of peat and root starter was used. I have been giving the tree calcium to slow the fungus that is attacking it. This has seemed to work a little bit. What fungicide should I purchase from my local nursery? I do know that my local retail store has Streptomycin, which usually is used for fire blight. (Niagara Falls, N.Y.)

A: Try a Bordeaux mixture to see if that arrests the progress of the disease. Streptomycin is strictly for fire blight bacteria and shouldn't be used off label.

Q: I dug up my flower bed a few days ago and now have hundreds of iris plants. We cut the leaves to about 2 inches and stood them up in a lawn wagon. I gave a garbage can full to a friend. If I don't get around to replanting, how do I store them during the winter? (e-mail reference)

A: Store them in a cool, dark location. Keep only the healthiest rhizomes and dust them with sulfur, which helps prevent rot and insect problems. You would be better off making an extra effort to get them planted this summer or early fall.

Q: I planted a Cleveland select callery pear tree this spring. As I was looking it over yesterday, I noticed it is covered with ants and the leaves are starting to turn black. Do you have any suggestions for our baby? (e-mail reference)

A: The ants are probably helping to "milk" the aphids that are feeding on the pear. Get rid of the aphids and the ants will disappear, too. Get some Sevin insecticide and spray the entire tree-covering both leaf surfaces. Repeat the spraying in 10 days. That should take care of the problem. Sevin is a short residual insecticide.

Q: I planted several Concord grape vines during the past few years. I got a couple of very tiny grape buds this year, but they dried up and died. What am I doing wrong? (e-mail reference)

A: Everyone always assumes they are doing something wrong when a plant fails to perform to their expectations. Grapes need pollinator activity to set viable fruit, but there is a shortage of bee activity throughout the country. When the flower cannot be pollinated by bees, the resulting fruit usually atrophies. It is not your fault, just a shortcoming in nature's network.

Q: I planted an ornamental pear that was doing great, but now the leaves have turned a dark red/burgundy color. The leaves are not falling off, but obviously something's wrong. I walked through my neighborhood and saw that the exact same thing is happening to all the ornamental pears. What is the problem and what can be done? (e-mail reference)

A: It sounds like a very virulent fire blight bacterium is going through your area. You must have had some rough weather recently, such as high winds or hard rain, followed by humid, steamy weather, which is conducive to the spread of this disease. If all of the leaves are affected, there is nothing you can do except give the tree its last rites!

Q: I have web worms in my pecan tree. My neighbor cut the branches out and burned the branches on his tree. Because my tree is so tall, what else can I do to rid my tree of web worms? What is dormant oil and where can I find it? How do I apply it? Thank you for your assistance. (e-mail reference)

A: Dormant oil is used in the early spring while the tree is dormant. On pecan trees, it should probably be applied by a professional applicator. The oil kills the overwintering eggs, but has a low toxicity. Any garden supply store should have it.

Q: We live in southern California, but have a weekend home on Big Bear Lake, which is located in the San Bernardino Mountains (7,500 elevation). We plan on planting raspberry, blackberry and gooseberry bushes next weekend. Any tips to help us get started on the right foot? Our cabin is on hillside and gets plenty of afternoon sun. We have very dry conditions, but we do have a drip irrigation system. The soil is hard and not particularly good. (e-mail reference)

A: It is important to do all you can to modify and improve the soil. Use copious amounts of organic matter, such as sphagnum peat moss or well-aged compost. Extensively work it into the planting site and don't worry about using too much. Set up your drip irrigation system to totally wet the entire area with each operation. When the soil is almost totally dry, run it again. If you don't know the quality of the water you are using, at least get it tested for soluble salts. Don't plant too deeply, which is a common mistake!

Q: I planted a bunch of privit amur a few years ago. It was doing well, but this year it appears that most of the woody branches died during the winter. However, a lot more new shoots are coming up from the base. What causes this and how do I prevent it from happening again? Also, I am looking for a fast-growing privacy screen that I can plant over an area that contains part of my septic system leach bed. However, I know certain plants like to break pipes in search of water. Can you recommend anything for my needs? (Morgantown, W.Va.)

A: Amur river privet is the hardiest privet on the market and should be hardy enough for Morgantown. It used to be a common hedge plant in Buffalo, N.Y. What I slightly suspect is that you were sold California privet, which is less hardy than the amur river. As long as it is coming back this season, I wouldn't worry about it. Don't overfertilize the plants. If you do any fertilizing, don't go beyond the end of August so the woody stems have a chance to harden off before winter. You are making a common, but incorrect assumption about tree roots. They do not break pipes in search of water. If the pipes are leaking, then the roots will follow a path to the water source. That said, I still wouldn't recommend a weeping willow as a tree to plant in the area. If you don't need anything too tall, try amur or tatarian maple, pekin lilac, gray dogwood or possibly the Laurel willow, which is not at all like the common weeping willow.

Q: I planted a maple tree in my yard two years ago. The problem is that the leaves have red pimples on them. What is causing this and what can I do? I live in the Turtle Mountains two miles west of Belcourt. The area is surrounded by pine and oak trees. The maple tree is located near a lilac bush. (Belcourt, N.D.)

A: Those red "pimples" (good description!) are actually erinium mite galls that developed as a result of mite activity very early in the spring as the leaves were beginning to unfold. Like pimples on humans, they don't look pleasant, but they are not causing any harm to the tree. They usually come and go as predatory mites discover them and eat them for breakfast. Spraying to control the mite galls is tricky at best and may have a negative environmental impact at worst. Sit back and enjoy the changes the tree will go through as the season wears on. Be sure to rake up and destroy all fallen leaves this autumn.


NDSU Agriculture Communication

Source:Ron Smith, (701) 231-8161, ronald.smith@ndsu.edu
Editor:Rich Mattern, (701) 231-6136, richard.mattern@ndsu.edu
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