Compost and Invasive Plants - Horticulture

Compost and Invasive Plants

Can invasive plants be disposed of in the compost pile? Read these tips to find out the answer and more.
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Ridding a landscape of invasive plants is a worthy but challenging cause. Physically removing every bit of every individual plant from the ground presents the most obvious challenge, but the project doesn't end there. The next step is to safely dispose of the plants. If not done properly, this task can undo all the good work you've just done.

Japanese Knotweed

(Shown: Japanese knotweed (Fallopia japonica, syn. Polygonum cuspidatum).)

The problem lies in invasive plants' ability and sheer determination to spread. After all, that's what makes them invasive. So simply dumping pulled plants on a compost pile or, worse, in a wild area of your yard, may very well give rise to new individuals.

The key to safely disposing of invasive plants lies in knowing the species and its method of reproduction. It is also important to ensure the plant is completely dead before completely disposing of it.

Woody plants that spread by seed. Examples: Japanese and European barberry, burning bush, buckthorns, bittersweet, multiflora rose.

It's best to pull them before they set fruit or seeds. Seal small plants or seedlings in a black plastic garbage bag, leave it in a sunny spot for several weeks, then take them out and compost them. (If immediately composted, they may take root in the pile and continue to grow and flower.) Larger plants should be laid on a tarp and covered with another tarp. Fasten the top tarp to the ground. Leave them to dry for several weeks, then they can be placed in a brush pile. Alternatively, pull them and immediately chip them to use as mulch or burn them. (Check with local government before burning any yard waste.)

Non-woody plants that spread by seed. Examples: dame's rocket, hogweed, knapweed, garlic mustard.

Pull them before they flower. Let them lie with their roots exposed until they are completely dried out, or seal them in a garbage bag in the sun for several weeks. They can then be composted.

Non-woody plants that spread by plant parts (stems, roots, rhizomes, bulbs, root fragments or buds, tubers). Examples: goutweed, thistle, loosestrife, Japanese knotweed, star of Bethlehem.

These should never be added to a compost pile or brush pile because they may root and sprout either in the pile or, in the case of compost, in the location where the compost is spread. Pull the plants and seal them in a heavy black plastic garbage bag. Leave the bag in the sun for several weeks, then dispose of it with trash, or remove the plants from the bag and burn them. (Check with local government before burning any yard waste.)

Your local extension agency or state Environmental Protection Agency may have detailed instructions on how to eradicate invasive plants common in your area. Your city or town may also offer guidelines on the disposal of problematic plant material.

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Learn the ins and outs of making great, safe compost with Let It Rot!, the classic guide now in its third edition.

Get ideas for replacing invasive plants in Great Natives for Tough Places.

Identify and eradicate weeds in your garden with Peter Loewer's Solving Weed Problems.