By Lindsay Bond Totten
Scripps Howard News Service
Answers to some of the gardening questions I've received recently:
Question: I inherited a lawn that appears to have zoysia grass mixed in with regular turf. Can I get rid of the zoysia without destroying the rest of the lawn?
Answer: No. But first make sure it's zoysia grass you have and not a healthy stand of crabgrass. Both turn straw-colored after the first frost. Crabgrass is "treatable," zoysia is not.
Zoysia is a warm season turfgrass variety better suited to the South than to the Northeast. While very drought-tolerant, it turns brown after a frost and won't green up until the weather warms — usually May in USDA Zone 5b. Zoysia is grown from "plugs," not seed, so a past owner must have planted zoysia intentionally in an attempt, perhaps, to fill bare spots in the lawn.
Unfortunately, there's no solution other than to kill off the entire lawn and start over, this time with turfgrass varieties — a mix of Kentucky bluegrass, perennial ryes and fescue — better suited to your climate.
Q: When purchasing a tree for my garden, the nurseryman asked me whether I wanted a single-stemmed or multi-stemmed specimen. What's the difference?
A: Primarily the shape and habit of the mature tree. I'll bet you were shopping for either a birch or a Japanese tree lilac, although Katsura tree, snowbell, silverbell and a few others are grown both ways.
The intended use should guide your selection. If the space is narrow, choose a single-stemmed tree so that low spreading branches won't get in the way. If the tree will be "open grown" — that is, by itself or in a bed combined with shrubs and flowers — a multi-stemmed specimen may look more graceful.
Just one word of caution: In the northeast, Katsura tree (Cercidiphyllum japonicum) is sometimes challenged by a canker disease. Multi-stemmed specimens seem more prone to infection than single-stemmed ones.
Q: By the time I planted my tomatoes last year, the plants had grown tall and leggy. I pinched them way back before planting — was that the right thing to do?
A: Pinching, even hard pinching, won't hurt tomato seedlings. But I'll bet it held them back a few weeks! Next time, just remove the lowest set of leaves (or two sets, if the seedlings are really lanky), dig a deeper hole and bury the roots and stem nearly to the lowest remaining set of leaves. It won't even hurt to plant the stem sideways in the soil. Roots will grow from nodes along the buried stem. Tomato plants treated this way are likely to adapt more quickly and bear fruit earlier than if they'd been pinched.
Q: I planted azaleas last spring. They seemed perfectly healthy when I bought them, but they wilted and died within a few weeks in my garden. I got no satisfaction from the nursery, but I'd like to try again. Any suggestions?
A: I'd try a different plant in that spot, perhaps red-twig dogwood, sweet pepperbush, hydrangea or ornamental blueberry bushes. If it absolutely has to be an azalea, try one of the deciduous varieties that tolerates wet feet, such as swamp azalea. The only natural phenomenon I know of that can kill an azalea as rapidly as you describe is drowning.
Q: I have a narrow walkway, which I'd like to edge with low-growing perennials. Everything I plant grows too tall, then flops over and blocks the driveway. Can you recommend some varieties to try?
A: You don't mention if your walkway is in the sun or shade, so here are some varieties for each: I like all of the barrenworts for edging in shade, but Epimedium youngianum stays somewhat smaller than the rest. Also, try golden variegated Japanese forest grass, lungwort and dwarf goatsbeard.
There are many more choices for a sunny walkway. Eliminating varieties such as catmint that tend to be too aggressive for narrow walkways, it still leaves gems such as moss phlox, dwarf sedges, pussytoes, cheddar pinks, and two of my very favorites Geranium catabrigiense "St. Ola" and Campanula portenschlagiana.
Q: I'm having a problem with black vine weevils. A nurseryman suggested applying Orthene, but I'd prefer a non-chemical treatment. Is there one that's effective?
A: Parasitic nematodes have proven as effective as chemicals in controlling black vine weevils. Of the two types most widely available, Heterorhabditis is much more efficient — nearly 100 percent — at killing black vine weevil larvae than Steinernema. Parasitic nematodes are safe to apply and have minimal impact on beneficials. Purchase them through garden supply catalogs that specialize in biological pest control.
Q: I've been advised to use sod instead of seed for my new lawn, but it's so much more expensive. Does sod really produce a better lawn?
A: In the long run, no. Seed produces just as good a lawn as sod, perhaps better, since you can customize a turfgrass mix to match your site. However, if you need a lawn quickly, or you must plant outside the narrow window of opportunity recommended for seeding a new lawn (early fall is best, early spring a distant second choice), choose sod. A sod lawn can be ready for moderate play within a few weeks; depending on conditions, a lawn that is started from seed can take several months.
(Lindsay Bond Totten, a horticulturist, writes about gardening for Scripps Howard News Service.)
