Weeds and Other Pests

What is a weed? That depends on your point of view. A weed to one person might be a beautiful wildflower or a source of food to someone else. You must decide which weeds and how many you are willing to tolerate in your lawn. Remember, a healthy lawn is not necessarily a weed-free lawn.

Most of the plants that we label as weeds are plants that can tolerate poor growing conditions. They thrive in conditions that other plants do poorly in, such as low nutrients or compacted soil. Because they survive in poor growing conditions, weeds can help you diagnose your lawn’s problems.

Many weeds are colonizers. They like bare soil and lots of sun, so they are the first to take advantage of newly disturbed ground. Weeds are able to grow quickly and produce huge quantities of seed, some of which can remain viable for decades.

Many weeds are plants that have been introduced from other countries. This has given them an advantage over our native plants, because the introduced species have escaped their natural controls like insect, pests, and diseases.

The best way to control weeds is to avoid creating the conditions that encourage weed growth. Follow the Safe Lawn guidelines of mowing high (3”) and leaving grass clippings in the lawn. Have your soil tested for pH and nutrients, then add slow release fertilizer in the fall if the soil indicates it is needed. Whenever you remove weeds, remember to spread some grass seed in the bare spot left behind, using a “northern mix” that is appropriate for our climate. Add some annual rye seed to the mix for quick sprouting. Then keep the seeds evenly moist until they sprout.

Permanent weed management lies in nurturing desirable plants the form a multi-layered groundcover within which weeds cannot get established. Use the following guide to address your weeds and pests safely and effectively.

Dandelion

(Taraxacum officinale)

Characteristics: A perennial with bright yellow flowers. Blooms most heavily in spring and has a long taproot. Seeds germinate throughout the summer.

Indicator of: Thin turf, bare soil.

Control: Dig out at least 4”-5” of the taproot and discard the plant. If you do this when the plant is blooming (but before it goes to seed), a time when it’s food reserves are the lowest, the remaining root pieces won’t have enough energy to send up another stalk. Reseed the area after removing. Or mow off flowerheads before they go to seed and use a grasscatcher to collect them. Discard all flowerheads. For dandelions growing in narrow cracks, pour boiling water on the plant. Corn gluten meal is a nontoxic “weed and feed.” (See box.)

Plantain

(Plantago major)

Characteristics:A perennial with a basal rosette of thick, smooth dark-green leaves. Many small, inconspicuous flowers cover a spike about 6-8” tall.

Indicator of: Compacted or poorly-drained soil.

Control: Dig up and dispose of the plant. Then re-seed the area. Aerate your lawn to loosen compacted soil.

Creeping Charlie

(Glenchoma hederacea)

Characteristics:A perennial that grows in sun orshade. A low plant with long creeping square stem and small lavender flowers. Smells like mint when crushed.

Indicator of: Poorly-drained soil and shady conditions.

Control: In the spring, raise the runners by raking, then mow them off. Be sure to dispose of the runners completely, because any pieces left on the ground will simply send out new roots. Or mix 5 teaspoons of borax with 1 quart water. (This will cover a 5’ x 5’ area.) Spray the mixture directly on the plant when it is in full bloom or after the first frost. Do not apply more than once per season, because it will kill the grass as well.

Hawkweed or Indian Paintbrush

(Hieraceum species)

Characteristics: A perennial with a yellow or orange dandelion-like flowers at the top of a stalk about 8-12” tall. The rosettes of hairy leaves often form extensive mats. They spread by underground stems and runners. Hawkweed blooms in summer.

Indicator of: Disturbed ground of low fertility, acidic or dry soil.

Control: Hawkweed is difficult to eradicate. Maintain dense turf and avoid bare spots to prevent it from getting started. Fertilize soil as recommended.

Chickweed

(Stellaria media)

Characteristics:A low-growing annual. It has a slender stem and tiny white flowers in small terminal clusters. Seeds germinate from late fall to early spring. Spreads by seed or underground runners.

Indicator of: Chickweed grows in many conditions, but it thrives in shady, moist areas.

Control: Dig out the plants and dispose of them completely, because seeds will continue to mature even after the parent plant dies. Chickweed is difficult to eradicate, so add it to the list of weeds you can tolerate.

Veronica or Speedwell

(Veronica serpyllifolia and Veronica arvensis)

Characteristics:A small creeping plant that forms mats. Cup-shaped flowers are pale blue with darker stripes.Heart-shaped seed pods. Seeds germinate in spring.

Indicator of: Thin turf, and shady areas with cool, moist soil.

Control: In the spring, rake vigorously to raise the runners and stems, then mow them off and remove them from the ground.

Thistle

(Cirsium species)

Characteristics:A biennial with a low rosette of prickly leaves that overwinter the first year. Large purple flower heads appear the second year.

Indicator of: Thin turf, low nutrients.

Control: Deep taproots and creeping underground stems make thistles difficult to eradicate. Dig out as much of the taproot as possible. Reseed the area after removing. Fertilize the soil as recommended.

Moss

Characteristics:A low emerald-green plant that forms mats on the ground surface. Mosses lack true roots and are often anchored to the ground just like thin filament.

Indicator of: Moist, shady conditions.

Control: Moss grows where it is too shady and moist for grass. Unless you are willing to work hard to improve the drainage of the soil and increase the amount of sunlight the area receives, you might as well add moss to the list of plants you can tolerate. You can also introduce other shade-tolerant ground covers.

Crab Grass

(Digitaria sanguinalis)

Characteristics:A grass with short, light green, hairy leaves on prostrate stems. Seeds germinate from spring through fall. Crabgrass is generally not a serious problem in Duluth.

Indicator of: Thin turf, mowing grass too short.

Control: Use Safe Lawn techniques to improve the success of more desirable grass varieties or plant a different ground cover,

Ants

Control: Ants like warm soil. To encourage the ants to relocate, pour lemon juice into the anthill. To eliminate anthills, you must kill the queen ant. To do this, quickly shovel the top layer of the hill and immediately pour boiling water into the nest. If ants are still present after a week, repeat this process.

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