Dallisgrass (Paspalum dilatatum) is a perennial, grassy weed found throughout the Southeast and southern United States. Its unattractive clumping pattern can be a problem in home lawns and although it is known to be difficult to control, various methods can be implemented to handle this problem in your landscape.
This weed thrives when fertilized with nitrogen, grows well in soils that are composed of clay or sand and can often grow much faster than turfgrass which allows it to overtake lawns easily.
One common characteristic of dallisgrass is its short rhizomes, which can root quickly and easily, allowing it to spread throughout the landscape. Since it grows in clumps, it will continue to enlarge its circle, even when the center of the weed has died. It’s typically coarser than turfgrass, greyish-green in color and produces tall, unattractive seed heads that are easy to identify.
Although it can spread by its rhizomes, its most common method of dispersal is through its seed produced in the spring and summer.
An individual plant can produce numerous seeds that germinate when the soil temperature is between 60–65 degrees. Mature plants grow best when the temperature is between 80–90 degrees; however, it is quite frost tolerant and has a long window of growth as it will often go dormant later than southern turfgrass species.
Pictured above from left to right: Dallisgrass growing in clumps and a dallisgrass seed head. The image of dallisgrass to the left is originally from Flickr.com.
Dallisgrass vs. Crabgrass
It’s not uncommon for homeowners and turfgrass professionals alike to confuse crabgrass with dallisgrass or vice versa. Both are grassy weeds that grow in clumps and can be difficult to remove.
However if both weeds are side-by-side, they’re easy to identify. For example, crabgrass has broader leaves that grow close to the ground. Dallisgrass grows to a taller height and has much larger seed heads that often have black spots on them that grow off the side of the stem. Crabgrass seed heads are smaller and grow out of the top of the stem.
Dallisgrass often thrives when nitrogen-heavy fertilizers are applied whereas crabgrass is often suppressed with thicker lawns.
Pictured from left to right: Crabgrass seed heads and dallisgrass seed heads.
Dallisgrass Non-Chemical Control
To take care of a dallisgrass problem, pulling or digging out plants can be an option. If the weed is young (before it has grown rhizomes and produced seed) and the problem is isolated, hand pulling may work. This is often best when the soil is moist so the roots can slide out of the soil more easily, but it may be necessary to use a tool to help you pry the weed out so that no roots are left behind.
Maintaining a lawn that is dense and has no bare spots will help to stop new dallisgrass seed from germinating. Developing and implementing a proper irrigation, mowing, and fertilization plan to keep your lawn healthy is your first defense against dallisgrass and other problematic weeds.
As previously stated, dallisgrass thrives when nitrogen has been applied excessively so choosing a fertilizer that’s not heavy in nitrogen or has slow-release nitrogen will help. If you aren’t sure how to select a fertilizer, check out How to Read a Fertilizer Label.
Seeds from dallisgrass can also stick to the blades of your mower so if it is an issue in one area of your lawn, save this for last and rinse your mower afterwards.
One of the best ways to maintain a thick, healthy lawn is to fertilize the lawn with the nutrients it needs. Here are some of our favorite fertilizers. You can learn more about them in Why Use Lawnifi Fertilizer?.
Dallisgrass Chemical Control
Pre-Emergent Control of Dallisgrass
Generally, the longer dallisgrass has been a problem, the more challenging it will be to control. Therefore, if hand pulling doesn’t work, chemical options may be your best choice and multiple treatments may be needed.
Pre-emergent herbicides are a great option that prevents weeds and should be applied in the spring before seeds start germinating. A pre-emergent, as its name suggests, controls weeds before they germinate and appear in your lawn.
Dimension (active ingredient Dithiopyr) is a popular choice and can also kill plants that have just recently germinated, making it a safe option if you are a few days late in applying. Another pre-emergent is Mesotrione. Mesotrione can be used as both a pre- and a post-emergent for dallisgrass.
Post-Emergent Control of Dallisgrass
For post-emergent control, which functions to control weeds after they’ve germinated, many homeowners ask us here at Sod University “Does Tenacity kill dallisgrass?”. As previously mentioned, Mesotrione, the active ingredient for Tenacity, serves as a great dallisgrass killer.
Systemic herbicides, including Mesotrione , are absorbed and moved throughout the plant’s system as a means of killing the entire plant.
Dallisgrass is notoriously difficult to control, so if you use chemical controls in your management plan make sure you read the label of the chemicals carefully to ensure that they are compatible and will not cause any damage to your lawn. For more information on weed control, check out Identifying Common Lawn Weeds or Weed Control in Your Lawn & Garden.