Deblen the Tree & Turf Doctor
Read your weeds
Read your weeds
Weeds can tell you a lot about the condition of your lawn and indicate what you need to
do to grow healthy grass that is naturally resistant to weeds and pest problems. Learn to
read your “weeds” for what they indicate about your lawn care practices and soil
conditions, and you’ll be on your way to creating a healthy lawn that will be less work in
the long run.
Reading weeds is actually very simple. First, know that weeds thrive in soil that is
compacted, poorly fertilized, and not pH balanced; and in lawns that are improperly
watered, seeded, and mowed.
Synthetic fertilizers and chemical pesticides also lead to undesirable conditions, which
restricts water and air movement in the soil. High nitrogen fertilizers can disrupt the
nutrient balance, accelerate turf growth, increase the need for mowing and contribute to
thatch buildup. Pesticides harm the microorganisms, beneficial insects and earthworms
that are essential to maintaining healthy soil, and therefore,
Use the following chart to identify the weeds in your lawn and correct the conditions that
are promoting them with the information below. For instance, blue violets often indicate
compaction and excessive watering. Aeration and proper irrigation would correct the
conditions that are promoting blue violet growth.
While we cannot provide specific information for every region of the country, and every
weed, this general overview will highlight the association of weeds with poor soil and
management conditions. And, while we don’t focus on pests, following the
recommendations outlined here will help alleviate many pest problems.
Remember, many plants that are considered weeds, have beneficial qualities. Try to
develop a tolerance for some weeds. For instance, clover - considered a typical turf weed-
thrives in soil with low nitrogen levels, compaction issues, and drought stress. However,
clover takes free nitrogen from the atmosphere and distributes it to the grass, which helps
it grow. Clover roots are extensive and extremely drought resistant, providing significant
resources to soil organisms, and clover will stay green long after turf goes naturally
dormant. Crabgrass provides erosion control, dandelions’ deep roots return nutrients to
the surface, and plantains are edible!
Common Lawn Weeds and What Contributes To Them
Eliminate the Conditions that Promote Weeds
1. Compaction – Compaction is an invitation for weeds. If your lawn is hard, compacted,
and full of weeds, aerate to help air, water and fertilizer to enter. If you can’t stick a
screwdriver easily into your soil, it is too compacted. Get together with your neighbors
and rent an aerator. Once you have an established, healthy lawn, worms and birds
pecking at your soil will aerate it for free!
2. Mowing Height – Bad mowing practices cause many lawn problems. Mowing lower
than 1 1⁄2 to 1 3⁄4 inches can kill the root system by preventing photosynthesis, and
mowing with a dull blade makes the turf susceptible to disease. A low mowing height
also invites sunlight in for weeds to sprout.
While grass species vary across the country, most lawns are a mix of kentucky bluegrass
and fine fescue. Generally, you should keep a lawn at 3- 3 1⁄2 inches. Mowing high allows
the grass to develop deeper, drought-resistant roots systems. For the first and last cut of
the season, mow to 2 inches. Do not mow more than 1/3 of the grass blade at a time.
Keep your mower blades sharp to prevent the development and spread of fungal disease,
or ask your service provider to sharpen their blades frequently.
3. Soil pH and Soil Testing – Low pH means acidic conditions and high pH indicates
alkaline conditions. If the pH is too high, your grass cannot properly absorb nutrients.
Ideal pH should be between 6.5-7.0, slightly acidic. Generally, lime is added to raise the
pH and sulfur is added to lower the pH, and adding compost can naturally correct your
pH. A soil test is highly recommended to determine the soil pH and specific nutrient
needs. Contact your extension service to find out how to take a soil sample. In addition to
nutrients and pH analysis, ask for organic content analysis, and request organic care
recommendations. Organic content should be 5% or higher.
4. Fertility -Soil testing is the best way to determine your soil’s specific nutrient needs.
Fertilizing in early fall ensures good growth and root development for your grass.
Nitrogen, the most abundant nutrient in lawn fertilizers promotes color and growth.
Adding too much nitrogen, or quick-release synthetic fertilizers, can weaken the grass,
alter the pH, promote disease, insect, and thatch build-up.
Your grass clippings contain 58% of the nitrogen added from fertilizers, improve soil
conditions, suppress disease, and reduce thatch and crabgrass. So, leave the clippings on
your lawn. You can use a mulching mower and leave the leaves too.
Compost is an ideal soil conditioner, adding the much-needed organic content to your
soil, and suppressing many turf pathogens. In the fall and spring, preferably after
aerating, spread 1⁄4 inch layer of organic or naturally-based compost over your lawn.
Compost tea and worm castings are also great additions.
Thatch is a dense layer of grass stems and roots on the surface of the soil. Thatch is a
symptom of shallow watering and chemical fertilizer usage. When thatch layers become
1⁄2” or more, the roots will grow up within the thatch instead of in the soil, making grass
susceptible to insects, disease, and weather stress. If your lawn feels spongy, you may
have thatch buildup. Thatch is reduced by aeration, topdressing with organic matter, or
power raking. In healthy lawns, earthworms and soil microorganisms break down the
5. Watering and Poor Drainage– Drought conditions, excessive watering or poor
drainage due to soil type are all invitations for weeds. Watering needs are very site
specific, but generally speaking, a deep watering of about one-inch once a week in the
early morning is best. Your type of soil impacts your drainage and is also site-specific.
Once you establish a deep root system from mowing high, you will need less water.
Check with your local nursery for more specific recommendations and your soil type.
6. Grass Seed and Seeding – Grass varieties differ enormously in their quality,
resistance to certain pests, tolerance to climatic conditions, growth habit and appearance.
Some weeds are the result of using poor quality grass seed. Over-seed with the proper
grass seed for your region to promote a dense turf that out-competes weeds. Consult your
extension service website to learn the best grass variety for your region and site
conditions (sun or shade). Your work to create a healthy lawn will help to protect public
health and the environment.