University of Vermont Extension
Department of Plant and Soil Science

Summer News Article

Purple Loosestrife is Not for Gardens

By: Dr. Leonard Perry, Extension Professor
University of Vermont

Purple Loosestrife (Lythrum salicaria) is an attractive perennial, but unfortunately not for gardens. Why?

You may be familiar with this plant, seeing the masses of purple along roadside ditches and in wetlands in late summer. It invades wetlands, eventually killing out existing plant species such as cattails, grasses and rare plants. It doesn't provide any food or habitat for wildlife. It may end up clogging drainage ditches, changing the wetland habitat, needed by birds and other wildlife, into a waterway. Or by capturing silt from streams, it may change a waterway into an eventual dryland instead of wetland habitat.

For these reasons the Purple Loosestrife is considered a noxious weed and illegal in at least 13 states to purchase and plant it. Vermont has no laws to legally ban such plants, but they do have a committee set up to research and provide information on such plants. You may contact them, and receive the free Invasive Plant Fact Sheet series from the Department of Environmental Conservation, 103 South Main St., Building 10 North, Waterbury, VT 05671-0408 (phone 802-241-3777).

"So" you ask, "I see this plant is bad news, but I don't have any natural waterways nearby. Why should I be concerned?" Each plant produces thousands of seeds which are spread by wind and birds, in addition to water. These can carry the tiny seeds quite some distance.

"Okay" you ask, "why should I be concerned with a few garden plants when there are already an estimated 3,000 to 4,000 acres in Vermont covered with this plant? What little impact will my few plants have?" This is a good question, and one I often get. But as noted above, even one plant can produce thousands of seeds, and so thousands of future plants which could make a significant impact on a wetland. Your sole plant might furnish the seeds to a wetland not yet invaded. And this wetland might have rare or endangered species in it which would be killed by the Loosestrife invasion.

"Okay," you admit, "I wont plant this. But what are my alternatives?" If you want a spike effect in the garden such as from Loosestrife, try the Obedient plant (Physostegia) which may also spread, but is not considered invasive. It also has a similar purple color as the Purple Loosestrife. If the color is key in your garden, not necessarily the upright spike effect, consider some of the fall asters (tall or low), some of the Speedwells (Veronica) which are generally 1 to 2 feet high and have flower spikes, or some of the perennial geraniums.

Check books in your local library or the internet for other potential alternatives. Mail order catalogs also have such information. And be sure and check with your full-service garden store for their suggestions for your particular locale.

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