Weeds Matter

Do weeds matter? An initial response may be ‘are you kidding me’!? Actually, weeds do matter! Did you know weeds provide clues of soil health and environmental factors? Some weeds are native plants and serve as a food source for butterflies and bees. This is part 1 of a 2 blog series where we discuss the roles of weeds particularly in lawns.

In part 1, we’ll discuss why the presence of weeds provide clues to the properties of your soil. We’ll learn organic strategies to reduce weeds in the lawn by first understanding the role weeds play in nature. This blog is targeted for those bound by HOA regulations or do not prefer a weedy lawn yet want to reduce chemical use and be more organic. If you can tolerate some weeds, then please stay tuned for part 2 (Pollinator Friendly Lawns) on how to manage a lawn to be aesthetically pleasing as well as beneficial for pollinators. Typically lawn maintenance is not discussed amongst wildlife advocates but lawn plays an important role with reducing water run off and increasing property value. Plus, let’s face it … lawns are everywhere so we might as well discuss it.

What is a weed?

What is a weed? A weed is a plant that grows where it is not intended, a “plant out of place”. What one person considers a weed may be a desired plant by others. It is subjective. Therefore, I rarely use the word ‘weed’ when I present horticultural topics but I’ll make an exception here. Learning why a plant grows in a certain area provides an understanding of what’s happening in the soil which is usually the root cause of many lawn issues.

What Would Mother Nature Do?

Why do we have weeds to begin with? The key to growing healthy plants (including grass) is healthy soil. When soil is poor, nature begins a process to repair it. One of those first steps includes pioneer plants which we perceive as weeds. When soil is disturbed or healthy topsoil is removed, pioneer plants grow from newly exposed seeds that were once dormant under the soil layer. These weedy plants include annuals and herbaceous plants that grow rapidly covering the soil surface. The plants grow, reseed, die, decay, and recycle nutrients back to the soil. This cycle gradually repairs soil by building up organic matter in efforts to sustain the next generation of plants: shrubs, pine trees, and understory trees. These larger plants eventually shade and suppress the weedy plants. The pioneer plants may survive for awhile but most will die out from unfavorable conditions and reduced sunlight.

Bad Reputation
front lawn
Our lawn in 2011 after a lawn company applied synthetic fertilizers for a year. We naively had no clue of the true harm we were doing to soil life. It was ‘green’ but not a healthy green.

Of course, some of you may be saying, I don’t have time to wait for weeds to repair the soil. Understandable. Plus, most HOAs will slap a fine or warning for unkempt landscapes with unsightly weeds. I do feel kind of sad for weeds and their bad reputations. They are trying to survive like you and me. Unfortunately, their negativity is echoed in the mega industry of lawn & garden care products. We spray weeds, kill weeds, pump soil with synthetic fertilizer, and do it again. Guess what? We’re nurturing a toxic environment and degrading soil life even more. In the majority of cases, poor soil is the reason we deal with weeds. Lipstick on a pig is still a pig. Poor soil with synthetic fertilizers is still poor soil.

“Topdressing” the Lawn

Many turf experts recommend “topdressing” lawns with a layer of compost twice a year. In the springtime, spread a half inch thick layer of compost on the lawn. In the fall time, repeat with a heavier application of compost, around one inch to 1.5 inches. Core aerate after a compost topdressing to amend organic material in the lawn’s native soil. This improves soil health, adds organic material, increases beneficial microbial activity and earthworms, and mimics what nature does to repair soil in a fraction of the time. Most importantly, improving soil health will naturally reduce weeds. Grass will grow healthier crowding out the weeds and suppress their growth.

Buying bulk compost is cheaper than bagged compost. If budget is a concern, I would prioritize compost topdressing in the fall season before the lawn is aerated and sown with grass seed. If you have a section of lawn that is always a trouble spot for weeds, then prioritize only that area. Compost topdressing will not give you instant gratification as chemicals do but the long term results are worth the investment. Your footprint for chemical and synthetic fertilizers will be reduced. The underground soil life will thrive resulting in a beautiful lawn.

Free Greens
henbit and purple dead nettle
Holding henbit in my hand. Purple deadnettle in the background.

As a wildlife advocate, I garden and recycle in ways that eliminate the need of chemicals and fertilizers. Take advantage of what weeds do provide: nutrients! I compost many weeds before their flowers go to seed. Consider it green manure like cover crops. Instead of spending money to buy NPK fertilizer at big box stores, steep weeds in hot water to make a free alternative. Your flowers and vegetables will appreciate some deadnettle tea! Some weeds are edible and make perfect additions in salads. Never eat a weed if you are not 100% confident of its identity. Hand-pulling, though tedious, is an effective way to control weeds but at least it comes with benefits.

Deep Watering
bittercress versus chickweed
Many weeds have shallow roots which will die off from less watering. (Left) Bittercress and (Right) Chickweed are winter/early spring annuals that thrive with frequent rainfall.

Deep watering is important for managing weeds and a healthy lawn. Most weeds, that grow as annuals, have shallow roots and rely on frequent watering. Many literatures provide a generic guideline to water the lawn one to two inches per week. This does not necessarily work for all lawns. Save time and money based on the condition of your grass and soil type. 

The appearance of grass provides clues when to water. If you walk on grass and see your footprint then that’s an indicator it’s time to water. I recommend you actually wait to see mild drought stress in the lawn before watering. When grass experiences this stress, a hormone (Abscisic Acid, ABA) is produced to encourage roots to grow deeper in the ground looking for water. You want grass to have deep roots so it’s more resilient especially during summer droughts.

Soil type also affects the duration time of watering. An intermittent water test provides informative data about your soil. For example, turn the sprinkler on and water the lawn for 15 minutes. Check for any water runoff. If you have runoff, then that means the soil needs more time to absorb water. Turn off the water and wait 45 minutes. Then water for another 15 minutes. Your goal is to soak the top 6” of the soil. Use a screwdriver test to measure depth. A screwdriver will penetrate soaked soil easily but will encounter resistance when it hits dry soil. Repeat the water intermittent test until you achieve 6”. 

Common Lawn Weeds

There are a gazillion weeds out there, and I use various mobile apps for identification. Below are only a few of the most common weeds found in lawns. Weeds can indicate a soil’s health, mineral deficiencies or surplus, ph levels, and soil types. The take away, if you want less weeds then strive for healthier soil. Healthy soil favors growth of grass, and grass outcompetes the majority of weeds.

Lawn Weed Profiles
speedwell
Bird’s Eye Speedwell
  • Veronica persica
  • Origin: Europe, Asia
  • Growth: Annual wildflower with blue flowers blooming from winter through spring. Dormant in summer.
  • Soil: Most soil types. Prefers disturbed soil. 
  • Wildlife: Early food source for bees

bittercress
Bittercress
  • Cardamine spp.
  • Origin: Europe
  • Growth: Annual. Early bloomer from late winter into spring. Compact, basal rosette. Difficult to eradicate; slightest touch pops seed pods
  • Soil: damp, open, or disturbed soil
  • Wildlife: attracts pollinators

chickweed
Chickweed
  • Stellaria media
  • Origin: Europe
  • Growth: Annual. Cool-season annual with white flowers and pointed oval leaves
  • Soil: Compact soil or poor draining soil. Soil ph slightly alkaline or neutral. Low calcium and phosphorus levels. High potassium and sodium levels
  • Wildlife: Bees attracted to nectar and pollen

clover
Clover
  • Trifolium spp.
  • Origin: Europe, Asia
  • Growth: Perennial. White flowers bloom from April through August. Prefers full sun and moist soil. Some lawn seed includes clover as an organic nitrogen fertilizer
  • Soil: Indicates a low level of nitrogen. High levels of chlorine, magnesium, and sodium
  • Wildlife: Attracts bees and a variety of butterflies

crabgrass
Crabgrass
  • Digitaria spp.
  • Origin: Europe
  • Growth: Annual, warm-season grass. Hard to eradicate once established. A single crabgrass can produce 150,000 seeds in a season!
  • Soil: Indicates low calcium, phosphorus, and humus. Acidic. High levels of magnesium, chlorine, and potassium
  • Wildlife: Used as a summer forage for grazing animals such as cows, sheep, and horses

dandelion
Dandelion
  • Taraxacum officinale
  • Origin: Europe, Asia
  • Growth: Perennial. Deep tap root. Yellow flower produces many seeds. Establishes in open patches in lawn
  • Soil: Indicates acidic soil. Low in calcium. High in potassium and chlorine
  • Wildlife: One of the earliest wildflowers to bloom. Early food source for pollinators. Seeds are eaten by small birds

henbit
Henbit 
  • Lamium amplexicaule
  • Origin: Europe, Asia, and northern Africa
  • Growth: Annual, squared stems with reddish purple flowers arranged in whorls in the upper leaves
  • Soil: Open, disturbed sites as well as lawns. Indicates high nitrogen. 
  • Wildlife: Early food source for bees and bumblebees

viola
Johnny jump up, field pansy
  • Viola bicolor
  • Origin: North America
  • Growth: Winter Annual. Native plant with blue/purple blooms from late winter into spring. It is common in disturbed habitats, fields, and along roadsides. Also known as field pansy
  • Soil: Clay, loam, sand. Disturbed soils. Acidic
  • Wildlife: Larval host plant for Fritillary butterflies. It’s an early food source for bees

plantain
Plantain
  • Plantago spp.
  • Origin: North America, Europe, Asia
  • Growth: Perennial or biennial. Medium green oval leaves. Short white hairs. Pictured is Plantago virginica
  • Soil: disturbed soil, heavy clay, low fertility, slopes, sandy soil
  • Wildlife: The Common Buckeye butterfly uses the plantain family as a larval host plant

Purple Deadnettle
  • Lamium purpureum
  • Origin: Europe, Asia
  • Growth: annual spring purple wildflower often confused with henbit. Upper leaves are triangular and distinctly red or purple-tinted.
  • Soil: It grows in many soil types thus not a good indicator for understanding soil. Grows on edges of lawn.
  • Wildlife: Flowers food source for pollinators.

Sorrel
  • Oxalis spp.
  • Origin: North America, Asia, Europe
  • Growth: Perennial or annual. Pictured is Oxalis stricta , yellow blooms. Forcefully expels seeds 12 feet away! The leaves fold at night and open during the day
  • Soil: Indicates low calcium and high magnesium. Poor and disturbed soil.
  • Wildlife: Bees, ants, and butterflies visit the flowers

Tiny Bluet
  • Houstonia pusilla
  • Origin: North America
  • Growth:  Annual. Native plant, small blue-violet flowers from mid-winter into spring. It adapts to rocky surfaces where grass can not grow.
  • Soil: Clay, sand, slightly acidic soil.
  • Wildlife: Early food source for emerging native bees (little carpenter bees, metallic bees, and small butterflies). Larval host plant of the Spotted Thyris moth (Thyris maculata).

Violet
  • Viola sororia
  • Origin: North America
  • Growth: Perennial. Blooms spring and sometimes late summer. Larger than the annual field pansy. A nice lawn alternative under trees since it tolerates shade unlike grass
  • Soil: Clay, Loam (silt), and sand
  • Wildlife: Larval host plant for Fritillary butterflies. Attracts butterflies and bees. Birds and small mammals enjoy seed fruits.

Published by all.i.plant

Horticulturist with an emphasis on improving biodiversity one yard at time. Organic vegetable and wildlife gardening.

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