Gardening: How to stop a chive blitzkrieg

  • Article by: NANCY ROSE , Contributing Writer
  • Updated: September 20, 2000 - 11:00 PM

QA bit of wild chives must have come in with a plant and now I have wild chives all over my perennial bed. How can I get rid of them?

ASeveral members of the onion family can become pernicious weeds in the garden. Species known as chives, garlic chives, wild leeks and field garlic can spread by seed and by bulb multiplication.

I love the late-summer white flowers of garlic chives (Allium tuberosum), but I missed deadheading a few of its developing seed heads and now it is spreading through my gardens.

To kill this pest you probably will have to combine hand-digging with spot herbicide treatments. First, dig up clumps, getting as much of the bulbs and roots as possible. If you see unwanted alliums blooming, be sure to deadhead or remove the plant before it seeds.

My garlic chives are astonishingly resistant to glyphosate (Round-up) herbicide at regular strength, in part because the grass-like leaves have a waxy coating that repels water. Try mixing glyphosate at a much more concentrated level, being sure to add a commercial spreader-sticker (an additive that helps the chemical adhere to leaves) or a few drops of detergent, then carefully brushing this mixture on the chives. Remember that glyphosate is nonspecific, which means it kills any green plant it comes in contact with, so apply it very cautiously around plants you don't want to lose.

QWe had retaining wall blocks installed around two 30-foot-tall 'Autumn Blaze' maples. Several roots 3 to 4 inches in diameter were cut off within 2 feet of the trunks. Will this damage the trees?

ASevering large roots is never a good idea, especially that close to the trunk. One large root is the beginning of an extensive network of progressively smaller roots, all of which are critical to your tree's ability to absorb water and nutrients.

Of equal concern is what changes in soil grading were done that made retaining walls necessary. Changes in grade can damage or kill trees. Because tree roots need oxygen not available at lower soil depths, the vast majority of tree roots grow in the top 6 to 12 inches of soil. Cutting and filling a slope can result in many roots being severed, and the remaining roots being buried too deeply.

Adding a few inches of soil to the existing level can kill sensitive species, such as white oak. 'Autumn Blaze' Freeman maple (Acer x freemanii), which is a hybrid of red maple and silver maple, is more vigorous and less sensitive to soil changes than white oak. However, drastic root removal and covering the remaining root system with excess soil will damage even this tough tree.

QWe have an ever-bearing rose bush, but after it flowers it forms bulblike things and doesn't rebloom. What should we do?

AYour rose bush is setting seed. These rounded seed structures are called rose hips. There is a lot of variability in seed production among the many species and cultivars of roses. I don't know what type of rose you have (tea rose, grandiflora, shrub rose), but your ever-bearing one should bloom repeatedly through the summer. The easiest thing to do is to deadhead your rose. Deadheading means removing a flower as it fades, before it has a chance to set seed. Use a sharp pruning shears and clip off the flowers when the petals start to fade and fall off. Deadheading benefits many annuals, perennials, bulbs and flowering shrubs, because it directs each plant's energy to grow leaves and flowers rather than produce seed. Because the plant's goal in flowering is to set seeds for future generations of plants, it makes sense that once it has set seed it tends to stop producing flowers.

Q

AI'd like to make sun-dried tomatoes. Can you sun-dry them in Minnesota?

It's unlikely that you could successfully use only the sun to dry tomatoes in this climate. There is too much humidity and not enough heat to dry the tomatoes quickly, which is necessary to keep them from spoiling before they dry. Many commercial sun-dried tomatoes are produced in parts of California that have arid climates. I have dried plum tomatoes (halved the long way, seeds removed) at the lowest setting in my oven, with the door slightly ajar for air circulation. Dehydrators made for drying fruits and vegetables are also on the market.

-- Nancy Rose is a research horticulturist at the Minnesota Landscape Arboretum. She spends her spare time gardening, inside or outside, depending on the weather. To ask her a gardening question, call 612-673-9073 and leave a message. She will answer questions in this column only.

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