Author Topic: Introduction to Common Weeds  (Read 1910 times)

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Introduction to Common Weeds
« on: April 27, 2011, 06:14:15 PM »

Color photographs of the weeds described here can be found in Weeds of the Northeast by Richard H. Uva, Joseph C. Neal and Joseph N. 
DiTomaso, Cornell University Press, 1997.

Ajuga or Bugleweed (Ajuga reptans) Description: Perennial; glossy green leaves arranged in tight rosettes; bluish-violet flowers in spring; spreads quickly by runners. Where it grows/what it likes: 
Shady areas. Beneficial uses: Great groundcover; attracts bumblebees; showy flowers and colorful leaves can be assets in an informal lawn. Control methods: Aerate soil to reduce compaction; add organic matter to soil; mow flower heads.

Common Chickweed (Stellaria media) Description: Annual; seeds germinate in early spring and late summer; slender, tender prostrate stems with numerous branches; leaves are opposite and about 1/2-inch long; small white flowers with five deeply notched petals; shallow fibrous root system. Where it grows/what it likes: Acidic, compacted, tight soil; prefers shade. Beneficial uses: Helps soil retain nitrogen; many varieties of birds like to eat it; high in vitamins; can be used to treat internal inflammation. Control methods: Boost organic matter in soil; maintain a thick, vigorous lawn; when weeding, remove plants from site completely as they tend to re-root themselves.

Clover (Trifolium repens) Description: Perennial; creeps to form patches in lawns; fibrous root system; dark green ovalshaped leaves with white crescent-shaped markings. Where it grows/what it likes: Sunny spots that are low in nitrogen and high in phosphorus; moist, low fertility soils. Beneficial uses: Helps fix nitrogen and make it available to other plants. Control methods: Add nitrogen to the soil and decrease phosphorus; mow high; mow flower heads.

Crabgrass (Digitaria sanguinalis) Description: Annual; germinates in late spring and becomes a pest in mid- to late summer; reproduces by seed; leaf blades are flat and 1/4- to 1/2- inch wide with sheaths that have long stiff hairs. Where it grows/what it likes: Compacted soil; thrives in hot weather when cool-season turf grasses are dormant; often found along driveways, sidewalks or in pavement cracks; usually means soil is low in calcium. Beneficial uses: Common heat-loving grass used as a lawn grass in warm climates like Florida; good forage food for ruminant livestock (such as cows). Control methods: In early spring, aerate bare patches to reduce compaction, topdress with compost and liberally apply grass seed; use corn gluten meal in early spring when forsythias bloom; you can reduce crabgrass by 50 percent just by cutting the lawn at 3-1/2 to four inches during the month of peak crabgrass germination (for six to eight weeks beginning when forsythias start dropping their blooms).

Dandelion (Taraxacum officinale) Description: Broadleaf perennial; seedlings have oval cotyledons with smooth surfaces; leaves exude a milky juice when cut; yellow ray flowers form dense heads; each head produces many plumed seeds that are readily dispersed by wind. Where it grows/what it likes: Moist weather and acidic soil; usually means the lawn is being mowed too low; can be a symptom of lack of calcium in the soil. Beneficial uses: Edible; sheep and cattle like to eat it; attracts beneficial ladybugs; the long roots aerate the soil and enable the plant to accumulate minerals, which enhance the soil when the plant dies. Control methods: Mow high, avoid overwatering and hand weed beginning in spring and continuing until new growth stops (when temperatures drop to 42 degrees Fahrenheit); raising calcium levels will help turfgrasses better compete with dandelions.

Ground Ivy or Creeping Charlie (Glechoma hederacea) Description: Creeping perennial; round to kidney- shaped leaves with toothed, rounded edges; spreads quickly by long, creeping shoots called runners. Where it grows/what it likes: Moist soil, thrives in shady, compacted areas. Beneficial uses: Historically used as a curative tea. Control methods: Fertilize in fall, regularly overseed, mow high and add organic matter to the soil; aerate to reduce compaction. The University of Minnesota suggests using borax to control creeping Charlie because the weed is more sensitive to boron than grass is. Dissolve 10 ounces of Twenty Mule Team Borax in 1/2-cup of warm water (or in enough water so it actually dissolves). Dilute this solution with enough water to total 2- 1/2 gallons. Spray the mixture evenly over 1,000 square feet of lawn. (Test a small patch of lawn first.)

Moss (many species) Description: Soft, ground-hugging plants lacking water-conducting tissues and roots. Where it grows/what it likes: Shady areas where the soil is acidic, moist, heavily compacted and infertile; can grow in areas heavily treated with limestone if there is deep shade and the soil is very moist. Beneficial uses: Beautiful groundcover. If grass won?t grow where moss is, let it flourish and enjoy it. Control methods: Test soil to determine acidity and nutrient levels, add proper amendments, reduce compaction, fertilize properly and aerate soil; provide enough sunlight for turf grasses to outgrow moss, perhaps by pruning trees or other vegetation that shades the soil where moss flourishes; rake moss away with an iron rake, and reseed; do not overwater.

Broadleaf Plantain (Plantago major) Description: Perennial; smooth, oval leaf blades two to six inches in length; leaf veins converge at the base into a broad leaf stem; fibrous root system; germination increases as temperature increases. Where it grows/what it likes compacted soil, moist areas. Beneficial uses: Helps to maintain lawn fertility; leaves are commonly used as medicinal poultice to treat poison ivy and insect bites. Control methods: Aerate soil to alleviate compaction; avoid overwatering; hand weed young plants; pop off seed heads in summer; add organic matter to the soil to enhance soil health.

Wild Violets (Viola papilionacea) Description: Perennial; heart-shaped, waxy leaves; fibrous root system; spreads aggressively by branching rhizomes and seed. Where it grows/what it likes: Shady spots and moist, fertile soils; often spreads from woody areas into newly established lawns. Beneficial uses: Flowers edible; pretty purple and/or white flowers add color to a lawn in spring. Control methods: Hand pull small clumps, being sure to remove roots; reduce shade; allow soil to dry out.