Managing Invasive Plants at Home: Resource List

Written and compiled by Kathleen G. Connolly, 11-3-22

Contents

Site-Clearing and Plant Removal Methods ............................................................................................................................. 1

[a] Repeated cutting or mowing ......................................................................................................................................... 1

[b] Forestry mowers ............................................................................................................................................................ 2

[i] Metal mesh over Japanese Knotweed ............................................................................................................................ 6

[j] Organic Herbicide: .......................................................................................................................................................... 6

Information resources ............................................................................................................................................................ 7

Purchasing topsoil and compost: ............................................................................................................................................ 8

“Blight” .................................................................................................................................................................................... 8

Plant blindness: ....................................................................................................................................................................... 8

Disposal ................................................................................................................................................................................... 8

Site-Clearing and Plant Removal Methods

leaves are pale-colored. Roots stores are naturally depleted by early-season leaf creation. When the young

leaves and stems are cut, the roots aren't replenished and the plant is weakened. (FYI: In many plants, stems

and trunks can photosynthesize.)

Cutting works slowly compared to other techniques. It may take multiple cuttings per year over multiple years

for woody plants. One of its benefits is that soil remains undisturbed, so that weed seeds are locked below the

surface. Also, even if the unwanted woody plants regenerate in the year they are cut, they may not produce

seeds in the current year, or even several subsequent years.

Read about knotweed reduction through systematic scalping: Nix the Knotweed

https://www.facebook.com/NixtheKnotweed/.

shredded chips on the ground, though it is usually not enough to achieve a wood chip smother (described later

in this document). Unfortunately, viable seeds and shoots may be present in the shredding. Roots will be

injured but not killed. Therefore, this form of mowing is only the first step. Subsequent steps might include

other methods, for example:

1. Leave chips lie fallow for up to a year and spot-remove any unwanted regeneration. Spot removal could

involve a variety of techniques, including hand-pulling, excavation, or cut-and-paint for the most difficult

weeds such as knotweed, bittersweet, or swallow-wort.

2. Cover the mowed area with 12" depth of raw wood chips fresh from "clean" tree takedowns. ("Clean" =

absence of invasive vines or other unwanted vegetation). Fresh chips are best. (See section on woodchips).

People often ask, “Should I replace topsoil after sod cutting?” The answer depends on the intended plants and

the results of a soil test. If replanting lawn grass (including a low-mow lawn), a 2" – 6" application of fresh

topsoil with 5% organic matter may be desirable. If planting warm season bunching grasses such as little

bluestem and native wildflowers, you might not amend the soil at all.

Remember: Rich topsoil is well-loved by many weeds. Also, many New England native plants evolved in the

region's acidic, low-nutrient soil. It is usually not a good idea to import nutrient-rich soil for this type of

planting.

[e] Smothering with black plastic (A.k.a. "Occultation") can be very effective in summer because it heats

embedded roots with temperatures as high as 110 degrees +/- and deprives plants of sun, air, and water. The

technique works best with herbaceous plants such as lawn grass and broadleaf weeds, which should be

winter. Others are very efficient at surviving winter weather. Leave the cover in place until August 1 of the

following year or later (see notes below). Remove newly germinated weeds with a rake or hoe. Supplemental

methods may be needed, particularly for mugwort, euphorbia (spurge), swallow-wort, and other incorrigibles.

[f] Solarizing with clear plastic (A.k.a. "Solarizing"): This approach uses UV-tolerant greenhouse plastic film,

with four mil thickness. In hot climates, such as the Southwest, clear plastic is a good choice. In the northeast,

solar orientation is critical. If the location has strong south or southwest-facing exposure, this technique may

create enough heat to be effective. Cut existing vegetation very close to the surface and remove it. Place the

plastic directly on the soil.

On a north or northeast orientation, clear plastic acts more like a greenhouse for weeds. In this orientation,

 Neither of these is effective with Japanese knotweed.

 Before applying any plastic, cut existing vegetation very close to the surface and remove debris.

 Use sandbags or long metal posts or long boards to secure the edges. Do not use staples or otherwise

develop holes in the cover.

 Overlap the edges if necessary. Take note of the likely wind direction and take care to put the higher

overlap above the edge that could be pulled by wind. (See diagram)

 Unwanted plants can sprout almost any time of year. If you keep the area smothered for a full twelve

months (or the better part thereof), all embedded plants will encounter the destructive effects of the

barrier.

 After removing the plastic, allow at least two months to allow unwanted plants to resprout. They

custom-cut for greenhouses, roll-ends are sometimes available at reduced prices:

 See https://farmplasticsupply.com/plasticulture/weed-control.

 Sometimes, AM Leonard (www.amleo.com) has clear greenhouse plastic and black plastic remnants at

reduced prices. Call the sales team at 1-800-543-8955 for pricing and availability.

 Bootstrap Farmer: https://www.bootstrapfarmer.com/products/greenhouse-

plastic?_pos=4&_sid=347649039&_ss=r.

 Greenhouse MegaStore: https://www.greenhousemegastore.com/

 Griffin Greenhouse Supply: https://www.griffins.com/

Overlapping edges:

[g] Wood Chips for Site Preparation: The chips created after tree removals are excellent site-clearing material.

These chips are rough cut and include all parts of the tree. Pile them 12" deep or more over the intended

removal area. (Depth is key! This is not the same as mulching with decorative bark materials.) Before placing

the chips, you must mow or brush-cut the intended area as low to the ground as possible. Rake away the

cuttings. (Or use a bagger on the mower.)

Additional notes on the use of wood chips for site clearing:

 Note 1: Wood chips are not the same as bark mulch or other forms of landscape mulch. Bark mulch

decays quickly and uniformly compared to wood chips. Bark mulch tends to repel moisture. Deep bark

mulch is likely to create dry zones under the soil surface. Wood chips, on the other hand, decompose

more slowly. Most of the chips in a typical pile are wood—with comparatively little bark. Wood is

"hydrophilic," attracting and holding moisture for longer times. Water infiltration and gas exchange are

unimpeded.

in southern New England. Eggs can travel with chips that lay on the ground. According to Annise

Dobson, Ph.D., Yale School of Forestry, try to use chips directly from a take-down. (They have not been

stored on the ground.) If the chips are stockpiled and rest on the ground, they may be pick up worms

or eggs. If using stored chips, allow the pile to compost for three days at 105 degrees or higher and

turn it. To get the latest on jumping worm solutions, visit ct.gov/CAES and use the search bar to search

for the topic: “jumping worms.”

 Note 4: Timing: Woodchip or woodchip/cardboard smothering can begin at any time of year. Leave the

material in place for at least one year for best results. After removing the cover, allow at least two

months to observe emerging weeds. There will be some unwanted plants, as embedded seeds can

remain viable for years. Remove undecomposed chips before seeding or planting plugs.

The drawbacks of cardboard are several, however. First, cardboard deprives the underlying soil of moisture

and air exchange. This deprives the roots of desirable trees and shrubs of water and air. (Keep in mind that

tree and shrub roots extend horizontally well beyond their canopies.) Second, it alters soil microbial

Organic farmers use weed-suppressing cellulose fiber paper. WeedGuard is probably the best-known

 Newsprint is generally considered safe, but it needs to be 3” to 6” thick to create an effective smother.

[j] Organic Herbicide: This group of herbicides has benefits, but a few drawbacks. Most organic herbicides

A few more points:

Books about invasive plants and weed management:

 Weed Control Methods Handbook, The Nature Conservancy, University of Georgia - Center for Invasive

on-your-farm-an-ecological-approach/

 Plant Blindess, a Mower, and One Unfortunate Afternoon: https://www.zip06.com/features/20200729/plant-

blindness-a-mower-and-one-unfortunate-afternoon/

Disposal

Plants, plant parts, and their seeds sometimes remain viable even after cutting or spraying. Some seeds can remain

viable for decades. It’s very important that invasive plants be thoroughly dessicated before they are added to the public

waste stream. Connecticut statutes govern invasive plant disposal, both aquatic and terrestrial. To find the statutes and

learn about acceptable disposal methods, download fact sheets:

 Guidelines for Disposal of Terrestrial Invasive Plants. University of Connecticut, CT Department of Energy and