GARDEN Q.&A.
Uninvited and Tenacious Guest
Q. A small area on our property has become infested with Fallopia japonica. My weed book says it is immune to herbicides, and it should be dug up. But roots kept breaking, and I'm afraid further digging would only make things worse. What else can I do?
A. Fallopia japonica is another name for Polygonum cuspidatum, commonly known as Japanese knotweed, false bamboo or, because it is so tenacious, other less printable things. Unless you deploy earth-moving machinery, expect to spend years fighting its remorseless advance.
But the knotweed battle can be won and, at least on the home garden level, without resorting to chemical warfare. (The plant is not immune to Glyphosate-based herbicides, but they are only partly effective.)
You do have to start by digging. Established stands have big underground rhizomes with vast stores of resprouting energy. You won't get anywhere if you do not get rid of them. Bits of root can make new plants, but the bits are small and weak compared with those powerful lumps.
After digging out the rhizomes, cover the area with heavy-duty landscape fabric and a thick layer of mulch. Shoots will still come through (knotweed can penetrate asphalt), and some will arise outside the mulched zone. But there will be fewer of them. Cut them off as soon as possible.
Keep cutting -- over and over, spring through fall. Eventually, roots deprived of above-ground growth will be starved into extinction.
Dividing Strawberries
Q. Two years ago this spring, I planted a strawberry jar with alpine strawberries. Most of them survived their first winter, but a few died, so I had to buy replacements. If it happens again this year, can I just divide the plants I have?
A. As long as the plants are large and healthy, they can be divided. And they will probably be all the better for the experience. Wait until they show signs of growth in early spring, then dig them up. Do not worry if loose dirt falls from the roots, but do not try to clean them off.
Look closely at the crown of a plant, right where it emerges from the soil. You will see that it is a bundle of growing points. Lay it on its side and use a sharp knife to cut it into two or three pieces, each with a couple of growing points and a good supply of roots.
Replant the pieces at the same depth, and water them well, using tepid water mixed with seaweed extract or other transplant fertilizer (following the instructions on the label). Keep the jar in the shade for a few days, so the pieces have a chance to recover.
That should take care of things for this season, but three years is the limit on potting soil. Plan to fill the jars with a new batch in spring 2005.
By then you may want some new plants, too. Sources for alpine strawberries (Fragaria vesca) include the Raintree Nursery, (360) 496-6400 or www.raintreenursery.com, and Bluestone Perennials, (800) 852-5243 or www.bluestoneperennials.com.
Garden Q & A