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WARNING: This week’s post does not contain any pretty lawn and landscape pictures. Only ugly pictures of dallisgrass infestations. If you only click on our emails for inspiring pictures, please do not continue. We promise to return to normal content next week.

Often the content of our weekly emails is the result of what we are seeing in lawns and landscapes. This time of year, while doing lawn evaluations for soon to be Hall | Stewart clients, it is common to encounter lawns with dallisgrass issues.

Let’s spend a few minutes learning about this invasive weed and learn why it is so important to “address it as soon as you see it.”

Dallisgrass is a perennial grassy weed that was introduced to the US from Uruguay and Argentina in the 1800’s by A.T. Dallis as a fast-growing forage plant. Unfortunately, dallisgrass liked the environment a little too well and soon was growing out of control.

Dallisgrass is a grassy perennial weed that is very noticeable this time of year in dormant bermuda lawns.

How fun would it be to bring to market a plant that is beneficial for generations to come and have it named after you! Poor A.T., he thought he was helping, but instead of a plant people love named after him, he has a weed with his name that is the catalyst for a lot of foul language.

Dallisgrass is often confused with crabgrass. Crabgrass is an annual, meaning it dies every winter and can be completely prevented with a pre-emergent. While dallisgrass is a perennial, a pre-emergent will prevent the spread of new clumps but repeated post-emergent grassy weed control is required to eradicate existing clumps.

What is Dallisgrass?

Dallisgrass is a coarse textured perennial that grows in an ever-enlarging circular clump and is often confused with crabgrass.

A perennial is a plant that comes back year after year. Dallisgrass goes dormant during the winter, but the rhizomes do not die. In the spring, new growth appears from the roots.

Dallisgrass has short underground rhizomes that gradually grow outward. It has wide ¼ to ½” leaf blades that grow 4-12” long when not mowed.

Mature clumps typically have dying centers while the outer edge continues to grow smothering turfgrass as it spreads.

Individual plants increase in size while new clumps start from weed seeds.

Dallisgrass flourishes in all soils, sandy to clay, but is partial to compacted, wet soils.

Dallisgrass is a very common problem for lawns throughout the south from coast to coast.

How To Control Dallisgrass

1. Healthy Turf - As with all weeds, maintaining a healthy, dense turf is the first step. Good mowing, watering, fertilizing and aeration practices result in a thick turf leaving less area for dallisgrass seeds to come in contract with and germinate. Thin turf and bare soil areas are an invitation to all weeds, especially dallisgrass.

2. Pre-Emergent Applications – Although dallisgrass is a perennial, it does produce an abundance of seeds that are spread by wind, animals and lawn equipment. Pre-emergent applications will not control existing dallisgrass, but it will prevent it from allowing more clumps to develop in your lawn. Seeds germinate in 60-65 degree soil temperatures, a few weeks after crabgrass germinates.

The second spring pre-emergent application between mid-March to early May is critical in stopping the spread of dallisgrass.

Dallisgrass goes dormant in the winter but the rhizomes stay alive and often keep some green color near the soil surface.

Dallisgrass grows outward smothering turfgrass as it spreads. Over time the center of the weed dies out while the rhizomes continue to spread.

3. Selective Post-Emergent Applications – Grassy weed control products labeled for crabgrass will work on dallisgrass, but repeat applications are required every 2-3 weeks until the rhizomes are completely dead. MSMA was the go-to product for years, but it is no longer available for home lawn use. One product labelled for homeowner use is Weed-B-Gone Crabgrass Killer. Always follow label instructions. Know your type of turf, and make sure the product is labeled for your turf type. Licensed lawn care professionals have restricted use herbicides available to use that provide better control of dallisgrass.

This lawn was overtaken with dallisgrass when we started working on it last spring. The owner agreed to allowing us to use glyphosate early in the growing season to aggressively control dallisgrass resulting large bare areas. Over the summer, most of the areas recovered. But another year of good turf management practices and this lawn is needed to return the lawn to looking great. Control of dallisgrass and recovery is often a two year process.

4, Non-Selective Post-Emergent Application – The best control of large areas of dallisgrass infestations where there is little to no desirable turfgrass remaining is to treat with glyphosate. Glyphosate is a non-selective herbicide, meaning it kills everything it comes in contact with. Repeated applications are still required. If spot treating clumps of dallisgrass in your lawn, take care not to allow the spray to reach desirable turf. Once the weed is completely killed, rhizomes included, resodding may be required.

5. Digging It Out – The most environmentally friendly, but the most time consuming and physically demanding, is to dig out the invasive weeds. A good step in preventing a dallisgrass outbreak is to dig out small clumps, rhizomes and all, as soon as you see them in your lawn.

Large areas of dallisgrass where little to now desirable turfgrass remains are best completely killed out with a non-selective herbicide and then resodded.

Non-selective herbicides were used in June to control dallisgrass in this lawn. After the dallisgrass was completely controlled, the areas were sodded with Bermuda.

Dallisgrass grows faster than turfgrass spoiling a well maintained lawn and landscape.

Because dallisgrass is a perennial, persistence is required. Total eradication of a large area may take more than one season. Multiple treatments over a two-year period can be expected.

It is one of the more difficult to control weeds homeowners will face and the longer it has been established the harder it is to gain control.

Address dallisgrass as soon as you see it. The longer you wait the more invasive it will become.

If you have dallisgrass problems, or if you need help in identifying dallisgrass, please give us a call or respond to this email.

Lorne Hall

Hall | Stewart Lawn + Landscape

(405)367-3873