Now for one of my favorite activities, answering your questions.
Q: My wife and I planted wisteria 10 years ago. It reaches our second-story patio and spreads about 30 feet horizontally on a trellis. Each year we sadly watched as other wisteria in the neighborhood blossomed but ours did not. It even gets its leaves weeks after the others.
Except this year! To our wonderment, we had a few clusters of leaves and three blossoms--one 10 inches long, another five inches and one mutant thing about one inch in length. Not all were on the same branch. We were so happy, we took pictures! What is wrong? My wife thinks it is too shady. It is under a white oak, but the oak doesn't leaf until after the wisteria flowers.--David Lanar
A: It's exciting when wisteria finally makes a show. Grown from seed, it will often not develop its well-known huge, pendulous, lavender, fragrant floral masses for 20 to 30 years. To make sure you acquire one that will flower, buy it in bloom. You saw one or two flowers this spring, so it should bloom next spring, albeit much less in shade, which retards growth.
Prune the long whips back to their woody stems in July, leaving only about three or four spur-shaped buds on each, to encourage flowering. You can also promote blooms by restricting the root run. Slice down eight to 12 inches deep about 24 inches from the trunk in a circle around it. Do this root-pruning with a square-edged digging spade. Err on the side of little to no fertilizer. Spread compost, such as leaf mold or a commercial product such as Leafgro, two inches thick over the roots but not against the trunk.
Q: Azaleas are in their splendor. Could you please print some sort of guidelines on when to prune so that next year's landscape does not suffer! Thank you.--Ellen Poor
A: Prune azaleas after blooming to correct an errant stem or a shrub that is a tad too tall. Selectively prune no more than one-third of the foliage now. But, it doesn't have to be pruned. New growth on azaleas is what forms the flowers for next year. If you need to cut more than a third, do it in early March. You'll sacrifice a season's flowers, but it'll renew to a fuller, smaller plant in one year.
Q: Is it safe to move a viburnum that is outgrowing its location? The plant--I'm sorry I don't know the variety--is about four feet tall, at least as wide and about seven years old, I think. I'd like to move it to a place where it has more room to grow, but I won't if it's likely to die. Thanks.--Jennifer Scott
A: You can move most viburnums. The safest practice is to root-prune it now and move it next year before it leafs out. Root-prune by sliding a square-edged digging spade down into the soil 12 inches from the base of the branches. Slice down about eight to 10 inches deep, all the way around the two-foot-wide root ball.
To move it next March, prune the top branches lower and narrower and dig down just outside the root-pruning cut. At about eight to 10 inches, slice under the roots, lift the shrub and move it on fabric that will hold the ball together. Don't plant it with the material around the root ball. Plant with leaf mold or other compost and water it.
Q: I have a water lily that remained in my container pond through the winter. Should I prepare to repot it as I would any plant that needs expansion or leave it and just add a fertilizer tab? Thanks for your help.--Renee Peters
A: If the water lily has been in only a year or two, it will be fine. You'll need to repot it only if it's pot-bound or to divide the plant, and you could do it this weekend. Otherwise, add a fertilizer tablet and you're on your way to another year of floating flowers.
Q: My house is in southern Maryland. Its shrubbery consists mostly of junipers, azaleas and a type of holly with needle-like leaf tips. The plants receive direct sun for most of the day. The hollies and junipers are growing at an alarming rate, and the azaleas do not fare well. The hollies also are directly in front of long windows that come within a foot of ground level. The view will soon be obscured. Please describe how difficult it will be to dig up these plants after five years and recommend a slow-growth replacement.--Jack Arnold
A: Your dilemma is common. Someone didn't determine the mature size of the plants when installing them. Even professionals can overlook this basic point. I would have to see your exact situation--anything else is a guess. With that said, permit me to guess.
Because they were planted at the foundation, the hollies are quite possibly Nellie R. Stevens and the junipers a type of Chinese. The junipers are outgrowing their ornamental value, and there is no need to save them. Soil in southern Maryland is mostly coastal-plain sediment, and roots love the wide open spaces of the sand. Hollies should be root-pruned now. Slice with a square-edged digging spade into the soil around the entire holly about 18 inches from the trunk. In February or March cut the plants to a height of two to three feet, transplant them and water deeply.
Some full-sun plants to replace the hollies and stay low at your windows are crimson pygmy barberries, golden mop falsecypresses, Nikko (Deutzia gracilis) or goldmound and Japanese spiraea.
Q: We live in Gaithersburg, and tent caterpillars are attacking our rosebushes. Today I picked off from one to six caterpillars from each of about 15 bushes. A couple of bushes had a branch eaten nearly bare. We're not fanatically against chemical sprays, but we're trying to encourage ladybugs to fight aphids, which are a minor problem we have. So we haven't sprayed anything yet. What do you recommend?--Kathryn George
A: Though their damage is mostly cosmetic, the sooner the better for control of tent caterpillars. This doesn't seem to be an exceptionally bad year in the amount of tents, but they have been reported on some unlikely candidates like rosebushes.
My treatment of choice to preserve beneficial insects, such as ladybugs, is to put on a glove and break up the tent, grabbing a handful of caterpillars. Then take a hose with a hard spray pressure and wash out the tent. That's usually the end of them, with little damage to plants. You can also cut the tents out.
Lerner is president of Environmental Design in Capitol View Park, Md. His e-mail address is email@example.com.