It's time again to answer your landscape questions. Weather permitting, we have about another month for gardening.
QI planted a row of dragon lady hollies a few years ago. I've replaced two in the same spot. When I pulled the last one up, the hole was full of water. I dug an 18-inch-wide trench about one foot deep, filled the bottom with gravel and placed the holly on four inches of dirt. The level of the new plant is several inches above the yard. Each end of the trench has a 1-by-1-foot hole filled with gravel. Will this solve the problem? -- Pam Greenwood
AWet feet is a good guess for the demise of your dragon lady hollies. We had months of heavy rainfall, which raised the water table. Most evergreen hollies must be planted in well-drained soil. If the gravel bed you put under and around the hollies is draining the water away from the roots, then it should correct the problem. If the water sits in the gravel and doesn't drain, the plants can still die from standing in water.
If the plant thrives, you have corrected the problem. You can also add a four-inch pipe at the base of the gravel so the water that collects will drain away. The pipe should run downhill and be open-ended so there is no chance of water remaining in the hole, continuing to suffocate the tree.
I have been fighting wild violets in my yard for more than two years. Do you have any suggestions for getting rid of them? -- B. Power
Improve cultural conditions by testing and improving the soil and creating a better-drained, sunnier environment. To keep the violets out of areas where they are not welcome, hand pull or use a dandelion fork to lift the shallow fibrous roots and bulblets. You can also use herbicide by spraying foliage or keeping seeds from germinating.
Use a glyphosate-based material, such as Roundup or Kleeraway, when the violets are actively growing and before they flower in early spring. In the lawn, a broadleaf weed killer containing triclopyr is effective.
But you don't have to use a toxic chemical to treat the wild violet seeds. Try a corn gluten-based material, such as Wow Plus (available through Gardens Alive, www.gardensalive.com) or Corn Weed Blocker (made by Down to Earth, www.biconet.com). It keeps seeds from sprouting and takes several years of use to be effective, but it adds organic material to the soil. For a synthetic herbicide, use Dacthal this month and Dacthal or Halts Crabgrass Preventer in spring. Always follow labeled instructions.
I've had daphnes by my patio for eight years. It flourished and each winter bloomed with fragrant flowers. About a week ago, the leaves started drooping. Do daphnes have a short life span? -- Gardner Hathaway
It's not that they are short-lived; it's that they are temperamental and die for no apparent reason. My favorite daphne for fragrance and showy, white margined leaves is Carol Mackie. Ours has performed admirably for four or five years. It wilted, browned and completely defoliated late this winter and then bloomed profusely on bare stems and leafed out again.
Daphnes prefer well-drained soil not rich in nutrients. So irrigating and fertilizing is killing them with kindness. Try planting another in spring in a somewhat protected, well-drained spot, leaving about a third of the root ball above ground level. After the first year, let nature take its course and it should do fine.
In a recent article you said that daffodils can be planted now, but November is a better time to plant tulips. I get my bulbs this time of the year. I plant them when I get them. If I do not plant the tulips now, how do I store them? -- Umesh C. Mullick
Many spring flowering bulbs put down roots at soil temperatures of about 50 degrees. Tulips should stay out of the ground until soil temperatures reach this level. If you decide to wait, store bulbs in cool, dry conditions, such as the basement or garage, in a mesh bag filled with vermiculite or perlite, and away from mice. Squirrels will also dig up bulbs, especially tulips. When planting, you might want to cover the area with chicken wire to discourage digging and then mulch with an inch or two of compost or aged bark.
I have a zoysia lawn. When should it be fertilized? -- Thomas Baity
In this region, zoysia maintenance is generally recommended for the summer months. As for most warm-season grasses, my recommendation is to fertilize in June as growth begins. Zoysia doesn't have demanding fertilizer needs and is the most likely to best all the other weeds and create a thick carpet. My only problem with it is the straw color in fall, winter and spring. If it's in full sun, keep it cut to 11/2 to 2 inches in height during the growing season; remove thatch by raking it hard in spring or using a dethatching machine from a rental company. Aerate to allow the moisture and nutrients to reach the roots. Do this before fertilizing. Then spread a 10-6-4 fertilizer, or close equivalent, that consists of 20 percent or more water insoluble nitrogen (WIN).
About a third of my lawn has been invaded by zoysia grass, which I want to replace. I plan to do two treatments of Roundup this fall and remove it with a sod cutter in the spring, taking out two inches of soil with it, followed by another application of Roundup. Your thoughts about this approach, please. -- Bob Blanton
The time to use Roundup to kill your zoysia is June or July, when the grass is growing at its best. It will require two applications. Ten days to two weeks after the second application, till the dead grass, rake off and aerate. Using a sod cutter to remove the layer of zoysia is good. See if it grows back; do another application of Roundup, if necessary, and seed and water. A blend of dwarf, turf-type tall fescue or a mix of creeping bluegrass, red fescue and rye will work well. A non-toxic way to rid your lawn of zoysia is to lay landscape fabric weed barrier over the patches and leave the fabric tacked to the soil (use sod staples) for one full year. Next October, remove fabric and seed lawn as described above.
I cannot seem to find any information on the angel trumpet. Is it normal for the leaves to fall off? Will it leaf out again in the spring? -- Betty Grewelle
Angel trumpet, named for its 8-inch to 12-inch trumpet-shaped flowers, is a Brugmansia. There are species of this South American plant that will grow to 30 feet in the wild. But in pots and cultivation, they grow about six feet to eight feet tall. Because of the magnificent flowers and tropical foliage that they produce in a single season, some people treat them as annuals. Angel trumpets have fragrant white, yellow, purple, or red to orange-red flowers. They are tropical plants that won't survive winter without a greenhouse.
A friend, Hume McClure, keeps his angel trumpet growing in a container. He brings it in before the first frost, cuts it back and puts it into the basement, holding it over in a dormant state. It will get a little water in winter, if he remembers. After danger of frost, in spring, he waters and feeds it, puts it back outside, and it begins to grow again. According to McClure, it prefers cooler temperatures, 60 degrees to 80 degrees, and the flowers on his are just fading now. The minimum temperature they can survive is about 40 degrees.
I need to transplant a rhododendron that was planted next to the door, where it's too cramped. Is now a good time to do this? -- John Guion
The criteria used to determine whether to transplant or prune your rhododendron is how long it has been growing there. Up to five years after planting, you can move a rhododendron rather easily and safely. I prefer transplanting them in spring. They are shallow-rooted plants that like to grow in exceptionally well-drained soil with lots of composted leaf mold. To dig the root ball, cut a wide area around the base of the plant -- width is more important than depth. Keep the roots moist but not soaking wet in the first year after transplanting. Do not fertilize; use a growth stimulant such as Superthrive or one of the kelp or other sea-based products, such as Coast of Maine Fermented Salmon. It is very helpful to reduce transplant shock.
If the rhododendron has been in this location for a long time, it can be more efficient to prune the plant to fit the space. Prune it selectively in late February to early March. Cut one branch at a time, to a whorl of leaves or a lower branch. You will lose one year of flowers, but it will renew very dependably.
Joel M. Lerner is president of Environmental Design in Capitol View Park, Md. E-mail or contact him through his Web site, www.gardenlerner.com.