How to Get Rid of Invasive Plants Without Chemicals

Non-chemical control works best on small patches of shallow-rooted plants. For deep rhizomes, tubers and established trees, expect years of repeated cutting, digging or smothering, and accept that some stands will not be eradicated. Vinegar and boiling water kill top growth, not perennial roots.

That is the decision this page makes for you: if the plant has a root system built to survive, do not expect one afternoon of work to end it.

How to get rid of invasive plants without chemicals: start with the root

The University of Maryland Extension separates weeds into three groups, and the group decides the method:

• Annuals complete their life cycle in one year. Stop them before they set seed.
• Biennials grow leaves in year one and flower in year two. Kill the rosette before it bolts.
• Perennials live for years and regrow from roots, rhizomes, tubers or bulbs. These are the hardest to control, because any living underground part can start again.

Plant type	Best non-chemical bet	What usually fails
Annual or winter annual	Pull or mow before seed set; smother the ground	Letting it flower and drop seed
Biennial	Dig the taproot in the rosette year	Cutting the flower stalk after seed has set
Perennial with tubers or rhizomes	Dig every piece, or repeat cutting and smothering for years	One pass; tilling, which spreads fragments
Woody vine or groundcover	Cut stems at the ground; pull runners; repeat	Pulling only the top growth
Tree or shrub	Pull seedlings; cut sprouts repeatedly, or use cut-stump treatment	Cutting a mature tree once and walking away
Lawn weed	Rake or pull rooted stems when soil is moist; keep turf dense	A single spring pass

Pulling and digging

The University of Maryland Extension says hand-pulling and digging work best when plants are young, small and the soil is slightly moist. Annual weeds have finer roots and come out more easily. Perennials need as much of the root structure as you can get, and simply breaking off the top will not kill them.

Three rules make the difference:

1. Pull at the base, not the leaf. Grab the crown or stem where it meets the soil and pull slowly.
2. Follow the root. For taproots, use a trowel or hori-hori knife and lift the whole root. For rhizomes, dig wider than the patch.
3. Expect to repeat. Maryland Extension says perennial root structures can be spread by cultivation, and regrowth may need several passes.

Do not till a patch of perennial weeds to “start clean.” Maryland Extension names Canada thistle, bermudagrass and mugwort as plants that can get worse after tilling, because every cut piece can become a new plant.

Cutting schedules

Cutting removes the top growth without killing the roots. Maryland Extension puts it plainly: perennials with well-established root systems will not be killed by mowing or trimming, though repeated cutting can keep them under control.

That does not make cutting useless. Repeated cutting can starve a perennial by forcing it to spend energy on new shoots. Maryland Extension says mugwort kept growing after two years of repeated mowing, so “repeated” can mean many visits, not two.

Three examples show how the schedule changes by plant:

• Tree of heaven. Maryland Extension says a cut tree regrows from live roots and produces prolific suckers. Without herbicide, the job is to cut every new sprout promptly, before it can store energy, and keep cutting until the roots are exhausted. This takes more effort and time than a herbicide treatment, and the page says so.
• Japanese knotweed. Penn State Extension says cutting alone is not an effective suppression approach. Cutting is sometimes used to shorten the regrowth before a herbicide treatment, but on its own it does not exhaust the rhizome system.
• English ivy. NC State Extension says frequent mowing, like mowing a lawn, can starve an infestation if you mow all of it. On trees, cut the stems at ground level and remove the vines as high as you can reach safely; the upper vines will die.

For a cutting schedule to work, cut low, cut often, and cut the whole patch. A plant that is cut on one side and left on the other will keep feeding the roots.

Smothering and solarization

These two methods are often confused. Both use a cover, but they work differently.

Smothering (occultation) blocks light with an opaque cover: a reusable tarp, thick black plastic, cardboard or commercial weed block. Maryland Extension says four weeks is the minimum, and tough perennials with extensive roots need longer, up to a year or more. Japanese knotweed is one of the examples. Hold the edges down with rocks or boards, and do not leave a gap where a stem can reach the light.

Solarization uses clear plastic to heat the soil. Maryland Extension says to use it during the hottest part of summer, July and August, for at least two to three weeks and up to six. Remove visible vegetation, water the area, lay 3 to 6 mil clear plastic, and bury or pin the edges. Do not till afterward, because that brings up weed seed. Do not use solarization under the dripline of a tree, because it can damage fine roots.

Smothering is the better fit for a patch you want to plant later. Solarization is the better fit for a sunny, bare site in midsummer. Neither is a quick fix for a plant that can regrow from a root fragment left outside the cover.

Grazing

Grazing is a real option for large, heavily invaded sites. It is not a backyard fix.

• The USDA Forest Service lists prescribed grazing among cultural control methods, and notes that manual and mechanical work is labor intensive and can produce poor results when the tools are inadequate.
• A five-year Purdue Extension study of goats on multiflora rose reduced rose cover by an average of 40 percent. The goats also ate most native plants, and the researcher followed the grazing with a targeted herbicide treatment.

Purdue Extension’s summary is the honest one: prescribed grazing “will not eradicate invasive plants,” but in combination with cutting and follow-up it can treat certain infestations, especially on steep or overgrown land where equipment cannot go.

If you want to try it, you need secure fencing, water, shelter and a plan for the regrowth. Check local rules before bringing livestock onto a property, and do not graze plants that are toxic to the animals.

Vinegar, salt and boiling water: what they can and cannot do

These three are the most common “natural” suggestions, and the sources are clear about their limits.

Vinegar (acetic acid). Montana State University Extension explains that acetic acid is a contact herbicide. It damages only the plant parts it touches, and it does not move to the roots. Household vinegar is about 5 percent acetic acid; herbicidal products are 20 or 30 percent. It works best on young seedlings at the two- to four-leaf stage. Perennial plants are unlikely to be controlled, because they can resprout from roots even when the tops are killed. It is also non-selective, so it injures any plant it touches.

Boiling water. Maryland Extension says boiling water can kill some annual weeds when they are young and small. It can suppress perennial weeds by killing the top growth, but it is “not effective for permanently killing perennial root structures.” It is best used in cracks in pavement or other hardscapes, not in lawns or planted beds.

Salt. No extension source used for this page recommends salt for invasive plant control, and this page does not give a salt recipe. If you use a product, it must be labeled for that use. The label is the law.

None of these is a shortcut for a perennial with a deep root system. If the plant is Japanese knotweed, tree of heaven, lesser celandine or English ivy, the method has to match the root, not the leaf.

Per-species notes for plants WildScope covers

Plant	What non-chemical control can do	What it cannot do	Guide
Tree of heaven	Cut every new sprout promptly and keep cutting until the roots stop sending shoots, Maryland Extension says	A single cut does not kill it and can make the colony worse	Tree of heaven removal
Japanese knotweed	Cutting and smothering can weaken it; a tarp may need a year or more	Penn State says cutting alone is not effective suppression	Japanese knotweed removal
Lesser celandine	A very small patch can be dug if every tuber is removed	Penn State says digging is not recommended: tubers are easy to miss and you remove a lot of soil	Lesser celandine removal
Garlic mustard	Hand-pull the whole crown and taproot before the seed pods form	It will not clear the seedbank, which lasts for years	Garlic mustard removal
Poison hemlock	Digging is possible only if you can remove the whole 10-inch taproot, and Penn State says it is difficult	The sap is toxic and a skin irritant, and trimmers also need precautions	Poison hemlock removal
Giant hogweed	Do not handle it casually; ask your state agency or extension before removing it	NISIC says the sap can cause skin irritation and blindness	Giant hogweed profile
Creeping charlie	Tug rooted stems with a sturdy metal rake when the soil is moist, at the start of an infestation	Not practical for large infestations; stems break and regrow	Creeping charlie profile
English ivy	Cut stems at the ground, remove vines from the tree, and mow or pull runners repeatedly	Vines regrow from roots and stem pieces; it takes repeat visits	English ivy profile
Callery pear	Pull seedlings and shallow-rooted trees when the soil is moist, removing the whole root	Cutting a larger tree leads to resprouts unless the stump is treated	Callery pear profile
Burning bush	Pull seedlings under 2 feet and cut larger stems; follow with cut-stump or basal bark treatment	Mowing alone resprouts, and treated stems can send up new shoots for at least two years	Burning bush profile

Japanese stiltgrass is an annual grass, so the non-chemical goal is to stop seed rather than exhaust a root system. Pull or cut it before the seed heads open in late summer, and expect the seedbank to last for years. The Japanese stiltgrass profile explains the timing.

For the full stem-size decision and the replacement programs, see how to remove Bradford pear and Callery pear.

Two safety notes do not fit in a table. Poison hemlock is toxic in all parts, and its sap is a skin irritant. Giant hogweed sap can cause skin irritation and blindness. Do not start either job without reading the safety section of the relevant page and, for giant hogweed, contacting your state agriculture department.

When non-chemical control is the wrong tool

Stop and get site-specific advice if:

• The stand is large enough that you cannot finish it in one season.
• The plant spreads by rhizome, tuber or bulb and you cannot remove every piece.
• The site is in or near water. Aquatic rules and methods are different.
• The plant is poison hemlock or giant hogweed, and you cannot avoid contact with the sap.
• The plant crosses a property line, or you are not sure who owns the land.
• You are not sure of the identity, and a native look-alike may be present.

Your county extension office is the right first call. It can identify the plant from a photo and tell you what has worked locally.

Dispose of every fragment

Non-chemical control produces debris, and the debris can restart the infestation. Penn State Extension recommends heavy-duty plastic bags, double bagging, and leaving the sealed bags in direct sunlight for several weeks before putting them in the regular trash. Bag roots, rhizomes, tubers and seed heads. Do not compost them. Keep soil that contained roots on site, and clean tools before moving to another patch.

The invasive plant disposal guide covers bagging, solarizing and local rules.

Related WildScope pages

• Removal guides for the species-by-species methods.
• When to treat invasive plants if you decide to use a herbicide after all.
• How to dispose of invasive plants for the debris.
• Identification guides before you pull the wrong plant.
• How to get rid of invasive plants for the five-step overview.