Thistle not just a weed> Many varieties exist

Dear Readers:

I can tell that as winter creeps by, your thoughts are turning toward the garden and what you’ll choose to plant next summer.

Over the past couple of months, several readers have written asking about the culture of specific plants. I hope my answers are helpful to you all.

Each question answered in this column is about thistles of various sorts. I find it interesting that in just a month or two I have received several questions about thistles when I never was asked about them before.

You’ll see in the following questions that thistles, like many plants grown in Maine, range in beauty and ornamental value. “Thistle” is used both as a botanical description and as a generic name for the appearance of a plant. Just the sound of the word is prickly, dry and weedy. When considering the wide range of plants which fall into this group, it becomes obvious that some plants which lend themselves to one person’s beautiful gardens may be nothing more than another gardener’s weed patch.

Q: I am curious about a decorative stem that I bought at a craft fair. It had been sprayed silver and is lovely in a dried flower arrangement. I thought it was a thistle but was told it is “teasle.” It is larger than any thistle I’ve ever seen. Do you know where I could find seeds for teasle? J.A., Guilford.

A: Teasle, the common name for the herb Dipsacus sylvestris, is frequently used in dried flower arrangements. It has a sturdy stem which gives way to the prickly, oblong-shaped seed that some crafters spray with paint to accent color in their arrangements. I’ve seen seed for this hardy biennial in Vesey’s and Burpee’s mail order seed catalogs. If you don’t have access to these catalogs, consider looking in your local garden center for a small package of seed to try the plant in your garden. This plant is commonly considered a wayside weed throughout North America. At maturity it reaches 2 to 3 feet in height and is a prolific seed producer. It can become a problem plant in the garden if seed heads are not harvested before the mature seed falls to the ground.

Q: Can globe thistle be started from seed? If so, how should it be treated as to type of soil, depth, etc.? E.T., Newport.

A: Globe thistle, Echinops ritro, is a perennial plant which may be started from seed with a little care. The seed of globe thistle commonly has a relatively low germination rate. About 55 percent of the seed you start will actually produce a seedling, so think about how many plants you want in your garden and try to germinate at least twice as many seeds. You’ll experience the greatest success propagating globe thistle from seed if you germinate the seed in a room with 60 to 65 degree temperatures. The seeds need light to germinate, so leave them exposed or covered lightly once you’ve sown it over the potting medium. You should see the seed germinate in 14-21 days. Keep an eye on the moisture level of your soil. Be careful not to let the potting soil dry completely, and be equally careful not to overwater. Soil which is never allowed to dry slightly can promote seed rot and proliferation of soil-borne fungi which can cause dampening-off disease in your seedlings.

Transplant seedlings in full sun in the garden with 18 to 24 inches between each plant. Globe thistle does well in many types of soil, and like many thistles is tolerant of poor, dry soils. Avoid planting it in heavy, permanently wet soils. The plant takes about 10 months to bloom after germination, so don’t be surprised if your plants don’t produce blooms until next summer. Once the plant does produce blooms, however, it will be prolific for many years.

Q. I have what some people call “Canadian thistle” all over my land. Do you know how to get rid of this weed? D.W., Appleton.

A. Many people who have open land are all too familiar with this thistle and others like it. Are you sure your weed is the Canadian thistle? The Canadian thistle and its close relative, the bull thistle, are very hard to distinguish from each other. Both have the same growth habit. They have similar leaves with spines, and both produce purple flowers. According to Rick Kersbergen at the Waldo County Cooperative Extension, one way to distinguish the two plants is to examine their leaves when they have just germinated. The seed leaves — or cotyledons — of the Canadian thistle are sharp and pointed. Those of the bull thistle are smooth, with rounded edges.

It’s important to identify properly which thistle you have to make a decision on how to control the weed. The Canadian thistle is a perennial plant, and the bull thistle is a biennial. Hence, bull thistle is fairly effectively controlled by mowing or cutting the plant at the base before it produces more flowers and seed. This strategy prevents new seed from entering the seed bank in the soil and should decrease the abundance of the weed in your fields and pastures.

The Canadian thistle is not so easily controlled. Even if you’re conscientious about mowing or cutting mature Canadian thistles, the plant generally has enough food reserves in the root system to allow it to make a comeback in the same or in the next growing season. If you are persistent and repeatedly cut or mow the same plants year after year — weakening their ability to spring back with their root reserves — you may make a dent in the number of weeds present. Perhaps the most effective strategy to control Canadian thistle, one which should be used only as a last resort, is to swab or spray the leaf surface with a nonselective herbicide such as RoundUp. Be sure that you read the entire label on the herbicide container. Make sure it is suitable to use on the type of weeds you have. Always be sure to mix the solution properly and wear as much protective clothing as you can bear. Follow the label instructions explicitly.

Readers note: In late December, I mentioned Snow and Neally garden tools in one of my columns. Many of you have asked how to obtain more information on the gardening tool makers located in Hampden. To obtain a free product brochure or to locate a dealer near you, write to Snow and Neally, P.O. Box 876, Bangor 04402-0876, or call 947-6642 or 1-800-933-6642.

Diana George Chapin is the NEWS garden columnist. Send horticulture questions to Gardening Questions, c/o MaineWeekend, Bangor Daily News, P.O. Box 1329, Bangor 04402-1329. Selected questions will be answered in future columns. Include name, address and telephone number.