KNOTWEED FACTS

Knotweed is The Big Problem at the High Street parcel. It's taken over the south bank of the stream.  The invasive plant is why Dobbs Ferry (in consultation with the Conservation Advisory Board) hired goats for two years--to keep it under control. Watch the News12 story here.  

Info (from the Mountain Statesmen) You can also read NY gov info on Knotweed here. 

Japanese Knotweed, Polygonum cuspidatum: Polygonaceae is an invasive species that was originally introduced to North America from Asia in the late 1800s as an ornamental. 

It is a shrub like herbaceous perennial that can grow as tall as 10 feet. The stem of the plant is hollow and is sometimes confused with a bamboo stem. 

It is a large aggressive plant that grows quickly and densely. When in bloom, it has small white strings of flowers and bamboo like hollow stalks give it a misleading attractiveness.

While the plant can be invasive and cause issues with drainage of waterways, damage to structures, roads and break sewer lines, it is also, surprisingly, edible.

Forages take advantage of eating, raw or cooked, young shoots, growing tips of larger plants and unfurled leave on the stalks and branches. It is a major source of vitamin A and vitamin C. 

It also provides potassium, phosphorus, zinc and manganese. It has also been found to be a source of resveratrol, the same substance in the skin of grapes and in red wine that reduces bad cholesterol and lowers the risk of heart attacks. 

There are even several recipes to be found using Japanese Knotweed such as Wild Knotweed Jelly, Japanese Knotweed Bread and Knotweed Pesto to name just a few.

REMOVAL

Option 1 (note: we don't want to do this)

Someone suggested that we hire a super-expert pesticide applicator to inject the knotweed with glyphosate (roundup). We were resistant, but she said that’s the only thing that kills it. She has two guys we could get estimates from. She said where it is in the stream, it may start to grow though the concrete of the waterway.

Option 2 – pull and smother

For those who don’t want to use chemicals, a few techniques have been proven effective. Small, new populations are perhaps easiest to remove by hand pulling or digging. Use a shovel or digging fork at any point during the growing season to loosen the soil around the rhizome and extract the plant. Larger, well-established patches of Japanese knotweed are easier to control by smothering. Smothering is most effective in early summer once the plants have put on a significant amount of growth and have exhausted some of the reserves in their rhizomes. In the beginning of June, cut stems close to the ground and cover them with heavy 7-mil black plastic or non-woven landscape fabric. Put mulch on top of the smothering material to improve its appearance. Smothering can take upwards of five years.

Option 3 - Cut (like the goats did)
As the Delaware River Invasive Plants Partnership said: Repeated cutting of the stems reduces vigor and can eventually reduce the root reserves in some cases, particularly with small, isolated populations. Cutting is effective at any time during the growing season, but only when done repeatedly as it will result in new shoot emergence. Cutting greatly reduces the reserves in below-ground rhizomes. At least three cuts are needed in one growing season to offset rhizome production. Repeated cuttings must be continued until knotweed stops resprouting and must be checked regularly for any regrowth. Cutting is most effective when used in conjunction with either shading or herbicide. *
*we do not want to use herbicide

After each clean up:

Plant material should be bagged or burned, not composted.