To rid flower beds of Canada thistle, gently hand-pull young plants

BACKYARD Q&A

April 29, 2001

Q. I have Canada thistle growing in two of my flower beds, and I'm concerned about it spreading throughout my garden. I think I brought the seeds in on some manure I had delivered last spring. What's the best way to get rid of it without resorting to pesticides?

A. Canada thistle is a tough perennial weed. It can spread vegetatively from underground stems called rhizomes or from the huge number of seeds that blow from the attractive purple flowers. Gently hand-pull young plants whenever they emerge. You can also cut them with a sharp hoe right below ground level. This will slowly starve the plants. Never let them flower, and do not attempt to dig them up; you'll only encourage new plants from the cut rhizomes.

Q. I have grown the 'Celebrity' variety of tomato for the past 10 years with very good results. I have a small garden and try to squeeze in a dozen tomato plants. My wife bought some heirloom tomatoes last year at the farmers' market and now insists we grow some in our garden. The heirlooms may have a slight edge in flavor, but I heard they don't yield well. Which are the best yielders?

A. 'Celebrity' is a very fine hybrid, but I think you'll find that older, open-pollinated varieties can yield as heavily. Here are some cultivars that have grown well in a demonstration garden at the Home and Garden Information Center: 'Prudens Purple,' 'Brandywine OTV,' 'Tappy's Heritage,' 'Golden Queen,' 'San Remo' (paste), 'Amish Paste,' 'Big Rainbow,' 'Howard German' (paste), 'German Johnson,' 'Giant Belgian,' 'Pineapple,' 'Yellow Pear,' and 'Red Pear.'

Unlike 'Celebrity,' these are all indeterminate in their growth habit -- the plants will keep growing, so be prepared to provide adequate stakes or cages. Overgrowing plants can be pruned back.

THIS WEEK'S CHECKLIST

1. Prune out black-knot lesions from ornamental cherry and plum trees. They appear as dark swellings or galls on twigs and branches.

2. Plant "baby food" for butterflies this spring. The caterpillars of swallowtails feed on parsley, fennel and dill, and monarchs feed on butterfly weed (Asclepias).

3. Order your copy of the Maryland Master Gardener, a 440-page gardening guide that includes hundreds of color pictures to aid in diagnosing plant problems. Call the number below for more information.

Backyard Q&A is by Jon Traunfeld, regional specialist for the Home and Garden Information Center, Maryland Cooperative Extension Services of the University of Maryland. For additional information on these questions, or if you have questions of your own, call the center's hot line at 800-342-2507, or visit its Web site at www.agnr.umd.edu / users / hgic.

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