Weed Resistant Grass Seed

Overseeding your lawn will thicken the grass, helping it resist future weed invasion. However, it is best used on a lawn where the weeds are currently dormant What you need to know about buying grass seed for lawns in Maryland.

Will Overseeding Choke Out Weeds?

Overseeding your lawn will thicken the grass, helping it resist future weed invasion. However, it is best used on a lawn where the weeds are currently dormant or have recently been killed. Spreading grass seed on a weedy lawn won’t do much good. Weeds that are actively growing in your grass will steal water and nutrients from grass seedlings, causing them to struggle and die. For best results, attack lawn weeds with a weed killer, then overseed to create a healthy lawn that prevents weeds from returning.

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How Does Overseeding Help Prevent Weeds?

Overseeding your existing lawn with new grass seed fills in bare spots and contributes to thicker grass throughout the lawn. A thick grass lawn without bare spots shades the soil below, depriving weed seedlings of sunlight, killing them. Not only that, but thick growing grass pulls moisture and nutrients from the soil first, before weed seedlings can get to them.

  • Overseeding contributes to a thicker lawn.
  • Bare spots that have been overseeded with grass are less prone to weed invasion.
  • Lawns thickened by overseeding prevent weed seedlings from receiving sunlight and nutrients, smothering them.
  • Regular overseeding maintains a thick, weed-resistant lawn without herbicides.

Grass plants, like all plants, weaken and die naturally over time. By overseeding you replenish your lawn with new grass plants. This constant replenishment keeps your entire lawn thick enough that it continues to smother new weeds. This reduces the need to use chemical weed killers on your lawn.

Do You Need to Remove Weeds Before Overseeding?

Overseeding is most effective when you kill existing weeds before you overseed. This is because grass can’t choke out existing, established weeds no matter how thick it is. A lush lawn can only stop new weed seeds from sprouting. Also, any weeds that are present when you overseed will steal water, nutrients, and sunshine from your new grass seedlings. Wipe out the weeds to give your grass a fighting chance.

  • Remove existing weeds before you overseed.
  • Existing weeds won’t be killed or choked out by overseeding. A thick, overseeded lawn will only suppress new weed growth.
  • Kill established weeds or they will rob water and nutrients from your grass seedlings.

You’ll get more new grass sprouts from overseeding if you kill existing weeds first. Overseeding a lawn overgrown with weeds will get a poor yield. Your new grass will struggle to compete with the weeds. Paving the way for new grass by killing weeds is your best bet.

See also  Germinating Weed Seeds In Distilled Water

What is the Best Time of Year to Overseed a Weedy Lawn?

For the best results overseeding your lawn, you need to seed at the optimal time for your grass type. Warm-season grass lawns (such as Bermuda, Zoysia, and Centipede grass) should be overseeded in spring. Cool-season grasses (Kentucky Bluegrass, Fescue, Ryegrass) sprout and survive best when overseeded in fall.

  • Overseed warm-season grasses in spring.
  • Overseed cool-season grasses in fall.
  • It’s best to overseed when no weeds are present.

Another factor that makes overseeding in fall a great option for cool-season grass lawns is that few weeds will be present. Even if your lawn was infested with crabgrass in spring, by fall it will have begun to drop its seeds and die off. If you overseed in fall, your new grass will sprout and establish itself. By spring, the grass will be thick enough to prevent many of those crabgrass seeds from sprouting.

What is the Best Grass Seed to Use for Overseeding?

The best grass seed for overseeding is grass that will grow well in your climate. In regions with freezing winters, choose cool-season grass. In regions where winters seldom freeze, warm-season grass will perform best.

  • Seed with cool-season grass in regions with freezing winters.
  • In regions with mild winters, overseed with warm-season grass.
  • Match your grass seed to the variety of grass present in your lawn.

It’s also important to note that overseeding is the act of spreading additional grass seed over an existing lawn. It’s usually best to overseed your lawn with the same species of grass that is present there. This will create a uniform, beautiful lawn.

What Grass Will Choke Out Weeds?

The best grasses for choking out weeds in your lawn depend on your location. If you are planting warm season grass and wish to have a weed-resistant lawn, Bermuda grass is your best choice. It spreads through runners and roots to take over areas, which prevents weeds from getting a toehold.

  • Bermuda grass is the best warm-season grass for choking out weeds.
  • Kentucky Bluegrass is the top option for battling weeds in cool-season grass lawns.

Kentucky Bluegrass spreads faster than any other cool-season grass. It produces roots that form new plants in both spring and fall, meaning it self-thickens and fills in bare spots. If you want to weedproof your northern lawn, go with KBG.

Will Overseeding Your Lawn Get Rid of Weeds?

Overseeding a weedy lawn will not kill weeds on its own. However, thick grass growth produced by overseeding prevents new weeds from sprouting. In order to keep your lawn weed-free with overseeding, first, kill any existing weeds, then prep your lawn and spread new grass seed. The thick growth of new grass will choke out new weed seedlings as they attempt to sprout.

See also  Growing Good Weed From Bad Seeds

Grass Seed

Turf-type tall fescue is the recommended grass species for Maryland. It does well in all parts of the state.

Purchasing grass seed

  • Buy high-quality seed. Poor quality seed is low in viability and contains weed seeds or undesirable grass species.
  • Select a turfgrass species that is suited for the site conditions. Then refer to the University of Maryland Technical Update, TT 77 Turfgrass Cultivar Recommendations for Certified Sod and Professional Seed Mixtures in Maryland (PDF), for recommended cultivars.
  • All grass seed for sale has a tag or label on the package listing basic information that indicates the seed quality. Read the information before purchasing the seed to help achieve satisfactory results.
  • Grass seed labeled as ‘Maryland Certified Seed’ (tested for germination and purity by the Maryland Department of Agriculture) is available in select locations such as garden centers, turf supply stores, specialty seed suppliers, or farm supply stores and typically contains UMD recommended cultivars. If MD Certified Seed cannot be located, look carefully on seed tags for the type of grass, variety, percentage of weed seeds, and percentage of noxious weeds. Refer to Sample Grass Seed Label below.
  • For the majority of sites, tall fescue is the recommended type of grass. Refer to Seed Mixtures and Blends below.

Sample Grass Seed Label

  • Seed blend or mixture name created by seed supplier.
  • Lot number used to track seed information back to the original site of production.
  • The official date on which the germination test was conducted. To ensure a high germination rate use seed within one year of purchase. As seed ages, the percentage of viable seed decreases, resulting in poor establishment.
  • Purity is the percentage by weight of each type of grass and cultivar or variety contained in the blend or mixture.
  • Variety or type of grass and cultivar. Refer to the University of Maryland Technical Update (PDF) TT 77 Turfgrass Cultivar Recommendations for Certified Sod and Professional Seed Mixtures in Maryland for the list of recommended cultivars.
  • Germination rate is the percentage of pure seed that is viable and will grow.
  • The origin where the seed was produced. Oregon’s ideal weather conditions for seed production of cool-season grasses makes it a large producer of quality grass seed.
  • Name and address of seller or supplier

Other crop seeds

  • Inert matter including chaff, soil, and debris. This value should be as low as possible. Inert matter is contained in the bag but doesn’t actually grow.
  • Percentage by weight of other agriculture crop seeds or undesirable grass seed. This number should be between zero and 0.5%. Avoid purchasing seed that contains Lolium multiforum (annual ryegrass), also called Italian ryegrass. This annual grass is found in inexpensive grass seed, only lives for one year, and makes it difficult for the desired grass species to become established.
  • Percentage by weight of weed seed. This number should be close to 0.00%.
  • Avoid purchasing seed that lists a percentage of noxious weeds.
See also  White Weed Seeds

Seed mixtures and blends

  • Seed is commonly sold in mixtures or blends.
  • A mixture is a combination of two or more grass species, e.g. tall fescue (should be the highest percentage), perennial ryegrass (no more than 5%-10% of the mixture), and Kentucky bluegrass (5%-10%).
  • A blend is three or more cultivars of the same species.
  • Mixtures and blends are popular because they increase the genetic diversity of your lawn. Certain grass species and cultivars are more susceptible to disease and insect problems, so using mixtures and blends increases your lawn’s ability to resist diseases and overcome insect infestations.
  • Mixtures are a good option if growing conditions vary throughout your yard. For additional information on seed, mixture recommendations refer to (PDF) TT 77 Turfgrass Cultivar Recommendations for Certified Sod and Professional Seed Mixtures in Maryland

High traffic areas

A mixture of turf-type tall fescue (90%- 95%) and Kentucky bluegrass (5%-10%) is an excellent lawn turf. The spreading root system of the Kentucky bluegrass will help the turf recover if injured from excessive traffic, drought, or pest damage.

Full sun areas

A blend of turf-type tall fescue or a single recommended cultivar.

Full sun to moderate shade areas

Turf-type tall fescue is recommended. A single cultivar or a blend.

Growing grass in shady areas

Fine fescues are the most shade tolerant of all the cool-season grasses, with hard fescue being the best choice for Maryland. Warm-season grasses, like zoysia, need full sun and are not suitable for shady areas.

How much grass seed to plant?

Grass-type Lawn establishment grass seed rate Overseeding grass seed rate
Turf-type tall fescue 6-8 lbs. per 1,000 sq. ft. 4 lbs. per 1,000 sq. ft.
Kentucky bluegrass 2-3 lbs. per 1,000 sq. ft. 1.5 lbs. per 1,000 sq. ft.
Fine fescue 4-5 lbs. per 1,000 sq. ft. 2.5 lbs. per l,000 sq ft.

By Debra Ricigliano, Maryland Certified Professional Horticulturist, University of Maryland Extension Home and Garden Information Center (HGIC), 2019. Reviewed and edited by Jon Traunfeld, HGIC Director, and Christa Carignan, HGIC Coordinator, Digital Horticulture Education.
Based on HGIC publication HG 102 Lawn Establishment, Renovation, and Overseeding.