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Updated Nov 03, 2022

Take a Year-round Approach Using Many Methods

Many people want to manage their garden and landscape without weed killers (herbicides). Herbicides are chemical products designed to kill unwanted plants.

Non-chemical weed control tips

  • Weed management in landscapes and lawns requires a year-round, integrated approach using many methods.
  • These methods work best when used in combination with each other or in addition to chemical weed-control methods.
  • Evaluate your tolerance for weeds. Strive to use non-chemical control methods first.

JUMP TO

  1. Understand Weeds’ Life Cycles
  2. Use Physical Weed Control Methods
  3. Prevent Weeds from Establishing
  4. Maintain Healthy Plants to Compete with Weeds

Keys for Success

  • Know how different kinds of weeds grow (life cycle). This information helps you determine the correct methods and timing for control.
  • Be realistic about weed control. Consider your expectations for your lawn, garden, and landscape. Match them with the time and effort you are willing to put toward weed control. Evaluate your tolerance for various weeds in different parts of your space.
  • Remove established weeds before planting. When possible, get them out with the root attached.
  • Plan your site with weed control in mind. Prevent weeds from establishing. Grow a thick lawn without bare spots. Use dense plantings and/or mulch to cover soil in landscape areas.
  • Remove new weeds quickly as they grow. Look for new weeds every 1–2 weeks. Remove them when the plant is small, before they are difficult to dig out.
  • Preventing weeds from going to seed reduces future problems.
UNDERSTAND WEEDS’ LIFE CYCLES

You often don’t need to know the species name or exact identity of various weeds growing in your garden and landscape to control them.

However, if you understand the life cycle of unwanted plants, you can determine the correct control timing and method.

Weed life cycles (how they grow) include:

  • Annual
  • Biennial
  • Perennial

ANNUAL WEEDS

  • Annual plants germinate from seed, grow, and set seed over the course of one year or less.
  • They often germinate in bare soil, exposed to sunlight, but also other areas.
  • For landscape areas, use mulch to prevent annuals from germinating.
  • Control annual weeds before seed matures to prevent future problems.
  • If you remove annual plants by the roots or cut them off just below the root crown (base of plant), they won’t grow back.
Common groundsel growing in dry creek bed landscape feature

"Senecio vulgaris" by Matt Lavin is licensed under CC BY-SA 2.0.

Annuals that sprout in fall and winter and then flower in the spring are cool season annuals. The photo shows common groundsel (Senecio vulgaris) in a dry creek bed landscape feature. The seeds float on air currents to new locations.

Crabgrass plant growing in brick patio

Joseph Berger, Bugwood.org

Annuals that sprout in spring when the soil warms and flower in the summer and fall are warm season annuals. The photo shows crabgrass (Digitaria spp.) growing in a brick patio.

Shiny geranium plant

Shiny geranium (Geranium lucidum) is an annual plant that grows 6–18 inches tall. It forms dense mounds that smother other vegetation. It often grows in landscapes and along roads, trails, and forest edges. Shiny geranium is an invasive plant species. Take action to control it.

Other common cool season annual weeds include:

  • Bittercress (Cardamine oligosperma)
  • Chickweed (Stellaria media)
  • Dead nettle (Lamium purpureum)
  • Annual bluegrass (Poa annua)

Other common warm season annual weeds include:

  • Pigweed (Amaranthus retroflexus)
  • Lambsquarters (Chenopodium album)
  • Mallow (Malva neglecta)

BIENNIAL WEEDS

  • Biennial plants complete their life cycle over two years.
  • During the first year, they germinate and grow as a rosette (low-growing plant). Rosettes are visible from the time of germination, through the winter, and into the spring.
  • In the second year they grow non-woody stems, flowers, and seeds. Many weedy biennials will survive more than two years under the varying conditions or if inadequate weed control is applied.
  • Dig out plants before they set seed and keep them from spreading.
Wild carrot flower head (umbel)

Becca MacDonald, Sault College, Bugwood.org

Wild carrot (Daucus carota) is also known as Queen Anne’s lace. Wild carrot plants grow a rosette in their first year. In the second year, they form long stems with white flower heads (umbels) at the tips as shown in the photo. Wild carrot attracts bees and other pollinators. It provides significant food resources for them.

Tansy ragwort flowers and stems

RuudMorijn, iStock

Tansy ragwort (Senecio jacobaea) is a biennial, non-woody (herbaceous) plant with yellow flowers. Tansy ragwort forms dense stands. It crowds out other herbaceous plants. All plant parts are toxic to people. Tansy ragwort is poisonous to some livestock.

Burdock rosette

Common burdock (Arctium minus) is a herbaceous, biennial weed. It often grows along roadsides and abandoned fields. The photo shows a burdrock rosette. The leaves are up to 20 inches long and 12 inches wide and heart shaped. In the second year, burdock grows a stem up to 5 feet tall and forms purple flowers and fruits with hooked bristles. The bristles stick to clothing and animal fur, which aids in seed dispersal.

PERENNIAL WEEDS

  • Perennial plants live two years or more. Perennial weeds include herbaceous plants and woody plants.
  • The best method to control perennial plants is to prevent them from establishing in the first place.
  • Established perennials are difficult to control. They often require several years of effort to get rid of them.

HERBACEOUS PERENNIALS

  • Herbaceous perennial weeds include dandelion, bindweed, Canada thistle, dock, and many others.
  • Watch for these weeds on your site and take action before they establish.
  • Dig out established plants by the roots. For example, you can remove most or all of the roots of dandelion and similar plants.
  • Many herbaceous perennial plants spread with underground roots. Remove as much of the root system as possible.
  • For situations where you can’t remove the roots of herbaceous perennial plants, focus on cutting the stems to remove leaves. The goal is to decrease the plant’s ability to perform photosynthesis. Over time, this process depletes the plants of carbohydrate reserves.
Dandelion flowering

Weston Miller, Oregon State University

Dandelion (Taraxacum officinale) is a common perennial weed. It has a long taproot that anchors it in the soil. You should dig and remove dandelion plants by the root. But they may regrow from small pieces of root broken off deep in the soil, so keep an eye on problem areas.

Canada thistle plants with pink bristly flowers

"Cirsium arvense" by Matt Lavin is licensed under CC BY 2.0.

Canada thistle (Cirsium arvense) is a perennial and spread by seeds and robust underground root systems. Mow stems several times per year to keep it from spreading. The seeds travel via wind to new locations. Until you remove the roots, it will keep coming back each year.

Mat of field bindweed growing with other weeds

telev_cat, iStock

Field bindweed (Convolvulus arvensis) has extensive root systems deep underground. New vines emerge from roots when old vines are removed. Keep bindweed from climbing up plants and fences by removing new vines as they emerge.

Perennial Grasses

  • Consider physically removing them by the root to keep them from growing back.
  • Perennial grasses are difficult to control, especially without herbicides.
Quackgrass leaves and stem

Steve Dewey, Utah State University, Bugwood.org

Quackgass (Elymus repens) is an invasive perennial grass. It grows up to 4 feet tall from seeds and creeping roots (rhizomes). It becomes a problem in landscape beds and other areas that are not often tilled. Quackgrass forms dense stands that suppresses crop growth. It out-competes native species in natural areas.

Black plastic on ground used for weed control

Master Gardener Volunteer, Oregon State University

Small patches of quackgrass and other herbaceous perennial weeds can be covered with a light-impenetrable barrier.

Tractor digging out jubata grass

David Chang, Santa Barbara Agricultural Commission

Heavy equipment is useful to dig out large perennial grasses such as jubatagrass and pampasgrass (Cortaderia jubata and C. selloana).

PERENNIAL VINES, SHRUBS / Bushes & TREES

  • Perennial vines, shrubs, and trees include tough weeds such as Himalayan blackberry, broom, tree-of-heaven, and many others.
  • Consider physically removing them by the root to keep them from growing back.
  • Woody perennial weeds are difficult to control, especially without herbicides.
  • Monitor where you remove perennial weeds for regrowth. Dig out plants as they regrow.
  • Controlling woody perennial weeds in the Pacific Northwest has a significant economic impact on public and private landowners.
Invasive blackberry taking over abandoned area

Invasive blackberry (Rubus armeniacus) is a widespread invasive plant that grows throughout the Pacific Northwest. It thrives in a variety of habitats. Blackberry spreads quickly and is difficult to control. Dig it out by the roots. Watch for regrowth and control it as needed.

Broom plants with yellow flowers along trail

Weston Miller, Oregon State University

Broom species (Cytisus spp. and other species) are evergreen shrubs with bright yellow flowers. Following control activities, look for broom regrowth and seedlings. Control them as needed.

Tree-of-heaven tree next to building

Weston Miller, Oregon State University

Tree-of-heaven (Ailanthus altissima) is an invasive tree that spreads quickly and is difficult to control. It thrives in abandoned sites. Roots must be killed or tree-of-heaven grows back. Controlling tree-of-heaven without herbicides is very challenging. Return to areas where you control it. Expect to re-treat for two or more years.

INVASIVE PLANTS

  • Invasive species are defined as non-native species that spread aggressively and alter the environment. There are many invasive plant species in the Pacific Northwest.
  • Controlling invasive plants requires specialized knowledge and methods specific to each individual species.

How to identify and control invasive plants and common weeds:

  • See Weeds for more information on how to identify and control invasive plants and common weeds.
  • Find specific control methods for each weed species.
PHYSICAL WEED CONTROL METHODS

WEEDING WITH HAND TOOLS

  • Dig out the roots of individual weeds.
  • Weed manually through the growing season every week.
  • Remove pulled weeds from your worksite.
  • Weeds left on the soil may re-root if the soil is moist.
  • For some weeds such as pigweed, if you remove the ones that have already flowered and begun to develop seeds, the seeds can continue to mature after the plant is pulled.
  • Put pulled weeds in the green waste recycling stream. You can also compost pulled weeds onsite.
Kale seedlings crowded by many weeds

Jen Aron, Oregon State University

The photo shows summer annual weeds between kale plants. The weeds need to be removed with hand tools at this stage to keep them from overcrowding the kale.

Freshly dug dandelion plant with root and leaves next to hori-hori gardening knife

Weston Miller, Oregon State University

Dig out dandelion and other herbaceous weeds by the root to kill plants.

Hand-pulled weeds including roots

Signe Danler, Oregon State University

Remove all parts of the plant when hand-pulling weeds. Dispose of weeds in yard waste or compost.

CULTIVATING

  • Preparing soil for planting (tillage) brings weed seeds to the surface and stimulates germination.
  • Expect many new weeds to germinate after you cultivate soil in your garden or landscape.
  • Kill young weeds 1–3 weeks after you disturb the soil surface.
  • Weeding activities also bring new weed seeds to the soil surface. Look for newly germinated weeds 1–3 weeks after weeding activities. Control them as needed.
Kale transplants with hoe and newly germinated weeds

Weston Miller, Oregon State University

The photo shows vegetable transplants, a hoe, and newly germinated weeds on bare soil. Cultivate the soil surface when weeds are small. Gently scrape the weed seedlings with a sharp cultivating tool. Repeat as needed until the canopy of your desired plants shades the soil to suppress weed growth.

Small tiller cultivating vegetable garden

"Mantis Tiller" by David Goose / MSI is licensed under CC BY-NC-SA 2.0 (cropped).

Use power tillers to cultivate the surface of the soil to kill young, small weeds. These tools don’t work well for large weeds. However, tillers damage soil structure and bring new weed seeds to the surface.

FLAME WEEDING

  • Flame weeding uses a backpack or dolly-based propane tank and torch. This tool effectively kills seedlings and low-growing plants.
  • This is most effective on smaller weeds.
  • Sites with significant annual weed infestations require flame weeding several times per year to keep plants from flowering and setting seed.
  • Check with your local fire department to make sure you can use a flame weeder in your area. Also, keep a hose or bucket of water nearby.
  • Use caution to keep from starting a wildfire if you choose to use a propane torch for weeding.
Flame weeder torch

Zack Snipes, 2019, Clemson Extension

The photo shows a worker using a flame weeder to kill weeds in a path in a farm field.

Many small weeds in soil

"Weeds" by Dwight Sipler is licensed under CC BY 2.0

Flame weeders kill young weeds such as the ones shown in the photo. Flame weeders work best for broadleaf weeds (dicots). They are less effective for grasses (monocots).

DIG OUT ESTABLISHED PLANTS

A selection of tools for removing woody plants

Weston Miller, Oregon State University

Dig out the root crown of woody perennial weeds. Use picks, shovels, or similar tools. A selection of tools for removing woody plants is shown in the photo.

Worker using weed wrench tool to remove a shrub

James H. Miller, USDA Forest Service, Bugwood.org

Manual removal of woody shrubs and small trees is effective but labor intensive. Using a Weed Wrench™ or similar tool makes it easier to remove larger shrubs. 

MOWING PERENNIAL PLANTS

Cutting back plants is an effective way to reduce their canopy so the root crowns and rhizomes can be located and dug out or treated with herbicides.

Worker using string trimmer

kn1, iStock

String trimmers with a blade attachment cut thickets of blackberry and other woody perennial plants. A tractor-mounted flail mower attachment effectively shreds blackberry canes.

Blackberry regrowth after mowing

Weston Miller, Oregon State University

After blackberry or woody perennials have been mowed, the plants will often regrow. The photo shows blackberry regrowth one month after mowing in the late spring. Further action is needed to control this patch of blackberry.

CULTIVATION, MOWING & REMOVING PLANTS WITH HEAVY EQUIPMENT

Tractor with disk attachment cultivating field

freeteo, iStock

Use a tractor-mounted disk harrow to control grasses and broadleaf weeds. Disking at the right time kills annual weeds. Disk after germination before plants flower. Perennial weeds like Canada thistle will regrow after disturbance. Control regrowth as needed to prevent plants from setting seed.

Tractor with mower attachment

sshepard, iStock

Carefully timed mowing limits weed seed production. After mowing, many plants will regrow and try to flower again. Repeat mowing and consider other control methods to keep weeds from setting seed.

Tractor removing invasive shrub

James H. Miller, USDA Forest Service, Bugwood.org

Use heavy equipment to pull or dig isolated bushes. Remove as much of the root system as possible.

TARGETED GRAZING

Grazing animals are used by ranchers and land managers to reduce the growth of weeds such as blackberry, yellow starthistle, knotweeds, and others.

  • Grazing is an effective way to reduce plant canopy so the root crowns and rhizomes can be located and dug out or treated with herbicides.
  • Grazing animals will eat desirable vegetation as well as the targeted weed.
Goat herd grazing

Repeated grazing is a good way to suppress plant growth. It is often followed up with other control methods.

Goat eating plant stems and leaves

Scott Bauer, USDA Agricultural Research Service, Bugwood.org

Contact professional pest control companies with experience grazing goats to control weeds. Or ask your Soil and Water Conservation District office for referrals.

PREVENT WEEDS FROM ESTABLISHING

SITE PLANNING TO PREVENT WEEDS

  • Establish a clean site by controlling perennial weeds before planting.
  • Plan landscapes to prevent weeds from entering or spreading.
  • Use the methods detailed below to prevent weeds in the first place.
Weed free landscape bed and compost mixed into the soil

Neil Bell, Oregon State University

Take the time to remove weeds in landscape beds before you plant. Before planting, dig out perennial weeds such as blackberry, dandelion, bindweed, or creeping buttercup. Remove the entire root system. Look for regrowth and follow up as needed.

Weeds sprouting in compost

Signe Danler, Oregon State University

The photo shows weeds growing in compost. Use weed-free topsoil and compost products, and nursery plants. Don’t bring new weeds to your site.

Concrete edging between lawn and shrub bed

Signe Danler, Oregon State University

Use edging to separate your lawn from landscape beds. Edging is attractive and helps to prevent grass from lawns from growing into landscape areas.

Seed spreader with lawn seeds

Weston Miller, Oregon State University

The best way to keep weeds out of your lawn is to grow thick, healthy turf. Provide lawns with water and nutrition. Apply seed over the top of your lawn at least every other year. The photo shows a seed spreader with lawn seeds on an established lawn area.

Large pigweed plant in landscape area

Stacy Kanan, Independent Consultant, Bugwood.org

Keep weeds from producing seed to minimize future weed problems. A single pigweed plant such as the one shown in the photo can produce 100,000 or more seeds. The seeds remain viable in the soil for many years.

Weed seeds stuck to a boot

SB_Johnny, CC BY-SA 3.0, via Wikimedia Commons

Don’t bring weed seeds that are on equipment or clothing to your site. The photo shows weed seeds attached to the worker’s boot and leg. Clean your shoes, clothing, and tools to keep from bringing new weeds onto your site.

USE HIGH-DENSITY PLANTING

Many weeds need exposed soil and many hours of sunlight to germinate and grow. Growing dense plantings of desired plants prevents weeds from growing.

Dense planting suppresses weed growth

Signe Danler, Oregon State University

A dense cover of low-growing plants prevents weeds from growing.

Native plants in landscape

Weston Miller, Oregon State University

Cover up bare soil in landscape areas with vegetation. The desired plants will shade the soil and keep weeds out.

ORGANIC MULCHES

Use a thick layer of mulch (3–4 inches deep) to keep annual weeds from germinating. Most weed seeds need exposed soil and a lot of sunlight to grow. Mulch limits the light on the soil surface that weeds require for germination.

Wood chips mulch around shrubs

Signe Danler, Oregon State University

Wood chips are an effective mulch choice for use in landscapes. Wood chips are often available for free. Ask tree care companies working in your neighborhood if they can drop off a load of chips for you.

Bark dust mulch between landscape plants

Neil Bell, Oregon State University

Carbon-rich mulch such as wood chips, bark dust, and straw helps to suppress weed seed germination. Mulch helps to conserve water. As it decays, it improves the soil structure over time. The photo shows bark mulch in a landscaped area.The look of this mulch appeals to many people.

Compost used as mulch with weeds growing in it

Neil Bell, Oregon State University

Compost is best used as an amendment that is mixed into the soil before planting. When compost is used as a mulch, weeds germinate and grow as shown in the photo. Carbon-rich mulch such as wood chips, bark dust, and straw are less likely to allow weeds to grow.

Get Wood Chips in the Portland metro area, Oregon.

In the Portland metro area in Oregon, CHIPDROP  is a service to get free wood chips delivered to your house, school, or community garden.

INORGANIC MULCHES

Inorganic mulches provide a physical barrier that limits weed growth.

Weed barrier exposed under bark mulch

Neil Bell, Oregon State University

Weed barriers (landscape fabrics) are applied under mulch. Weed barriers shade the soil and help to keep weed seeds from germinating. Add new mulch on top of the weed barrier every 1–2 years to keep the fabric buried. But weed seeds may germinate in the mulch. The roots then grow through the fabric. The fabric may tear when weeds are removed. Also, shifting mulch exposes the fabric over time, as shown in the photo.

Tomatoes growing with black plastic

Alton N. Sparks, Jr., University of Georgia, Bugwood.org

Use plastic mulch for annual plantings such as vegetables. Plastic mulch warms the soil as well as limits weed growth. Use thick black plastic sheeting from the hardware store. Or source biodegradable plastic from specialty grower supply stores. Plastic mulch is not recommended for permanent plantings.

Weeds taking over area mulched with rock

Signe Danler, Oregon State University

Rock mulch is not recommended as an effective method to suppress weeds. Weeds that become established are hard to remove. Rocks increase surface temperature. Dry stream bed landscape features use rock mulch. Put landscape fabric under the layer of rocks. You will need to remove weeds regularly to keep dry stream beds weed-free.

OTHER MULCHING METHODS

Layer of leaves on cardboard covering the ground

The sheet mulching method uses a layer of cardboard or newspaper as a temporary barrier placed on the soil surface. Then place a 3–4 inch deep layer of organic mulch such as leaves or compost on top of the cardboard. The cardboard layer breaks down over time. This method works to keep weed seeds from germinating temporarily. It doesn’t work to keep perennial weeds from growing.

Black plastic sheeting used to suppress weeds

Master Gardener Volunteer, Oregon State University

Use opaque plastic sheeting or a tarp to shade out weeds before preparing soil for planting. If you are planning to expand your garden or landscape, cover the area for 3–6 months with an opaque barrier. The barrier will keep annual weed seeds from germinating. The barrier deprives perennial weeds of light and weakens them.

Clear plastic applied tightly to soil surface for solarization

Karey Windbiel-Rojas, used with permission from the University of California Statewide IPM Program.

Soil solarization uses clear plastic secured to the soil surface to heat the soil and kill weed seeds and other pests. Follow these steps: Cultivate and rake smooth. Water to 8-inch depth. Cover the soil tightly with clear plastic for 4–6 weeks during mid-summer. Remove plastic. Avoid disturbing the soil at this time.

Maintain Healthy Plants
  • Weeds compete with desirable plants for space, water, sunlight, and nutrients.
  • Help your desired plants to establish and outcompete weeds by giving them the space, water, sunlight, and nutrients they need.
Fertilizer pellets at base of geranium

Signe Danler, Oregon State University

The photo shows white fertilizer at the base of a perennial landscape plant. Place fertilizer in the root zone of desired plants to promote robust growth and help keep weeds from growing.

Drip irrigation distribution tubing and emitters in landscape

Weston Miller, Oregon State University

The photo shows drip irrigation tubing and emitters next to a landscape plant. Drip irrigation is an effective way to water desired plants. It minimizes water application between desired plants and this helps to keep weeds from growing.

Sprinkler spraying water on bare ground

Sprinklers are an effective way to provide water for your plants. However, using overhead sprinklers to apply water to bare ground encourages weeds to germinate and grow.

Large leaved perennial

Signe Danler, Oregon State University

Provide your desired plants with the sunlight they need to grow. A dense canopy of desired plants shades out weed seedlings.

Content provided by editor Weston Miller and writers Signe Danler and J. Jeremiah Mann.

 Peer reviewed by OSU Department of Horticulture.

Photo of Weston Miller

Weston Miller

Project Founder and Content Writer

Weston Miller served as Community and Urban Horticulture faculty for Oregon State University Extension Service for Clackamas, Multnomah, and Washington Counties. Weston is an author for content for this website. He developed funding partnerships with Portland area agencies to initiate and build out the Solve Pest Problems website focused on this goals:

Signe Danler

Signe Danler (Editor/Writer)

Signe supports the OSU Extension Master Gardener Program by producing educational content for online Master Gardener training courses, and teaching and managing the OSU-Extension online Home Horticulture courses. She also designs residential and commercial landscapes, specializing in regenerative gardening and landscaping practices.

J. Jeremiah Mann

J. Jeremiah Mann

J. Jeremiah Mann completed a Physical Science undergraduate degree at Humboldt State University, and M.S, Ph.D focusing on plant science topics at UC Davis. He went on to work for the Natural Resources Conservation Service and in a leadership position serving a private agricultural technology company. He currently lives in Sacramento California where he consults on pest and property management topics.