Unlike other broadleaf weeds, crabgrass maintains a low profile in the lawn. The lower height of the weed makes mowing impractical to cut the plant. However, you can kill the invasive weed with a multistep process involving pre and post-emergent herbicide.
Crabgrass is a yearly problem that many homeowners face. The invasive plant is an annual broadleaf weed that grows and spreads in clumps.
Crabgrass reproduces every year via seeds. Each plant is capable of producing between 100,000 and 150,000 seeds in its lifetime. Once the seeds shed, they will germinate in the soil and spread like wildfire if not controlled. It's a frustrating weed to deal with. However, this article spells out how to kill crabgrass once and for all.
Step 1: Pre-emergent Herbicide
Pre-emergent herbicides prevent weeds from germinating in your lawn. After application, pre-emergent products act almost like a “force field” against crabgrass seeds.
Its best to use pre-emergent herbicides before spotting crabgrass in your turf. Once crabgrass begins to grow, pre-emergent herbicides will not kill it.
Apply a pre-emergent herbicide or weed and feed in the early spring. A general rule of thumb is to apply a pre-emergent product no later than the third cut of the growing season. The earlier in the spring you use a herbicide, the more time the pre-emergent has to work.
Make two to three applications of herbicide to ensure an adequate protection against crabgrass. Remember to moisten the lawn before application of granular products.
Some products may need watering post-application to activate and spread the pre-emergent herbicide. If you are looking to overseed, wait at least 90 days to apply it after using a pre-emergent. Many pre-emergent products will keep grass seeds from germinating or sod from developing.
Best Pre-Emergent Herbicides to Stop Crabgrass Before It Starts
HJ Crabgrass Control Plus is one of the best performing pre-emergent herbicides on the market. Designed to keep crabgrass from growing in any lawn, you can use this pre-emergent in almost any type of turf. Prodiamine is the active ingredient in the product. Prodiamine is designed to keep crabgrass, chickweed, spurge, carpetweed, and a host of other weeds from growing in your grass.
Application rates range from 3-9 pound per 1,000 sq ft. depending on the type of grass and infestation level. It is best to apply HJ's product when there is light rain in the forecast; the product needs half of an inch of rain after application.
Step 2: Post-Emergent Herbicides
Post-Emergent herbicides kills crabgrass after the weed has already started to grow. After the effectiveness of pre-emergent products fades, post-emergent products should be used.
Homeowners should apply a post-emergent product at the first signs of weed growth. Post-emergent weed killers interrupts the weed's metabolism processes, killing it to the root.
During the heavy growing season, you can apply many applications of post-emergent products. Use Post-emergent products on sod and established lawns in lower concentrations. Always follow the manufacturer's instructions and application rates when using herbicides.
Best Post-Emergent Crabgrass Killer for fescue, zoysia and bermuda lawns
One of the most powerful herbicides available for crabgrass is Fertilome Weed – Out With Crabgrass Killer RTS. It targets crabgrass as well as chickweed, morning glory, sunflower, dandelion, poison oak, thistle, and buttercup.
There is no seasonal restrictions for using Fertilome Weed – Out. You can use it during warm and cool weather and it is rainproof for an hour after the application.
Each 32-oz. bottle covers 2,500 square-feet.
Best Post-Emergent Crabgrass Killer for centipede lawns
Although designed for maintenance of deer food plots, Arrest MAX Herbicide provides the best control for Crabgrass in centipede lawns. Among other weeds, it also controls bermudagrass, barnyardgrass, broadleaf signalgrass, brome, crabgrass, fescue, foxtail, goosegrass, itchgrass, Johnsongrass, lovegrass, ryegrass, orchardgrass.
Simple to use, it is best to apply this product in spring or summer.
Best Post-Emergent Crabgrass Killer for St Augustine lawns
There is no perfect solution for crabgrass growing in St Augustine lawns. The best solution is to use Atrazine.
Atrazine will only suppress crabgrass, it doesn't kill it outright. However, using Atrazine combined with practices that encourage a healthy lawn, your St Augustinegrass can outcompete crabgrass to keep it from taking over your lawn.
Atrazine can also be used on centipedegrass, making it perfect if you have a mixed St Augustine and centipedegrass lawn.
Bonus: Recommended Weed & Feed Crabgrass Killer
Scotts Turf Builder and Crabgrass Preventer kills crabgrass and fertilizes your lawns at the same time. It delivers the nitrogen your lawn needs to green up. Also, it contains a pre-emergent herbicide (Pendimethalin) to prevent crabgrass.
After applying, ensure that the lawn receives between .25 and .50 inches of water for best results. You can use Scotts Weed and Feed and Crabgrass Killer on almost all residential lawns. Do not use the product on established or recently seeded lawns.
Do not oversee until at least 60 days after applying Scotts Crabgrass Killer.