Ask the Gardener: Tips for killing the Dracula of weeds

Ask the Expert
The unwelcome swallow-wort reportedly escaped from a garden in Cambridge in 1867.
The unwelcome swallow-wort reportedly escaped from a garden in Cambridge in 1867. Jennifer Forman Orth/National Park Service

What to do this week: My rain gauge in Milton registered 6 inches last week. Not normal! Keep on mowing until the grass stops growing, then run the machine until the gas tank is empty. Plant bulbs and divide perennials. Drain and store hoses. Turn off outdoor water taps and drain them, too, if necessary. Seek and pull weedy vines such as deadly nightshade or Virginia creeper that hide in hedges but have leaves that turn a different fall color. When emptying out annual container gardens, dump the exhausted soil mix into the compost pile to get recharged by microorganisms, then wash the container with a 10 percent bleach solution. Let it dry in the sun on a warm day before storing. Save seeds in the refrigerator or a cool room in glass jars with tight lids containing a few grains of powdered milk to absorb moisture.


Q. Is my jack-o’-lantern edible? Should I recycle it as a pie now that Halloween is over?

KRISTINA GRAHAM, South Pomfret, Vt.

A. Don’t feel guilty about dumping your pumpkin. It’s bred for appearance, not taste. The seeds and flesh are edible, but the seeds are neither tasty nor large, and the pulp is stringy. Boo-hoo!


Q. I am dealing with a lot of bittersweet and black swallow-wort. I have read your advice and used your clip-and-dip method successfully on bittersweet. How do I dispose of the cut vines? I put the berries in the trash. Can the vines go in the yard-waste collection? And do you have advice on dealing with black swallow-wort? Plants from my neighbor’s lilac hedge are turning up in my grass and gardens.


A. These two vines are so hard to kill, they must be related to Dracula. My organic approach with the worst invasive weeds and their seeds and roots is to seal them in large, thick black plastic trash or construction bags. Lay them in the sun and “solarize’’ them for at least a couple of months in sunny weather. The problem is that November is when people clean up their yards, but sunlight is in short supply. I have left these bad-weed bags out over the winter in a sunny spot out of view, and they have weathered the season fine and cooked their contents in spring and summer. Be especially careful to include all weed seeds, such as bittersweet’s orange berries inside bright, golden capsules.

There is an 1867 report that black swallow-wort escaped from a Cambridge garden, whose owner must have had weirdly Gothic tastes. Now it’s headed for the Midwest. (Moral: Be careful what you plant.) The seeds grow in narrow milkweed-like pods before going airborne on silky parachutes. In fact, swallow-wort looks enough like milkweed to fool egg-laying monarch butterflies, but it actually poisons these “mislaid’’ monarch caterpillars. A nasty trick! When are monarchs going to get a break? In fact, nothing eats black swallow-wort with its sinister pointy dark leaves and pods and tiny black star-shaped flowers (or its equally invasive cousin, maroon-flowered pale swallow-wort). Mow or clip swallow-wort vines to prevent the 2-inch pods from maturing, or else they will take over our planet (or at least your yard) like those sinister pods in science fiction movies. Ask the neighbors whether you can clip theirs as well. Seriously. I often help manage my neighbor’s invasive weeds in self-defense. The most effective time to cut is early July, after flowering but before the pods mature and produce seeds that are viable for five years. The best organic solution is to dig up the perennial root masses producing the vines, seal them in plastic bags, and leave them in the sun to heat up and melt down. Keep at it! Early detection and perseverance are your best tools.

There are lots of weeds, but only about five that will wreck your yard and your neighbor’s, too. So learn to recognize swallow-wort vine, Japanese knotweed, garlic mustard, porcelainberry, and bittersweet, and remove them before they get entrenched or permeate your soil with long-lived seeds. Don’t get distracted by relatively harmless cosmetic annoyances such as dandelions. They’re just the jaywalkers in a war zone.

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