Crabgrass is a terrible weed to have in our home lawns, it’s a very weedy and fast growing annual grassy weed that spreads very rapidly, and can be difficult to eradicate. If we have Crabgrass in our Saint Augustine lawns, then the very best way to remove this weed is to have an overall management plan for its planned removal - as well as its ongoing control. Having an overall strategy to control Crabgrass is the best way to permanently keep this weed out of our lawns.
Lawn Health and Lawn Mowing Heights
Our first step in controlling crabgrass is to ensure our lawns are in the best health possible, as a healthy Saint Augustine lawn will naturally fight off and keep out almost all infestations of Crabgrass. Good lawn care practices should be followed to bring our lawns to full health, such practices include following a good year round fertilization program, pruning surrounding shrubs and trees that may be causing excessive shade onto the turf, and watering correctly throughout the year.
Equally as important is to maintain the height of the Saint Augustine lawn at its correct height for this lawn type. Most modern soft leaf Saint Augustine lawns love to have a longer leaf than other warm season grasses such as Bermuda grass and Zoysia grass. So wherever possible, we should raise our lawn mowing heights a little higher. This is even more important when growing turf in higher shaded conditions. While Saint Augustine is very shade tolerant, we must always ensure we keep the leaf of our lawns higher whenever it’s growing in partial shaded areas.
A longer lawn leaf will ensure far greater photosynthesis in partial shade, thus creating a healthier lawn in these conditions, and a strong healthy lawn with a reasonable level of thatch, and a lush green leaf sward, will fight off Crabgrass on its own quite effectively. Regular lawn mowing will also remove more and more Crabgrass seeds as they are being produced and before they can spread out and reseed themselves.
Once we’ve got our lawn care, lawn mowing heights and regular lawn mowing practices sorted out, all of which will aid in the control of all weed types, we can now look at spraying the existing Crabgrass to kill it off.
Pre-emergent Crabgrass killer should be applied to the turf in the early Spring before the first Crabgrass weeds have even emerged. A pre-emergent herbicide kills the weeds as they are first emerging from their seeds, and it’s at this time that they are at their weakest and most easily killed.
Once the herbicide has been applied to the lawn, it is then lightly watered into the soil. Each Crabgrass killer product is different and will have different application rates and recommended procedures to follow for best results, so be sure to follow manufacturers recommendations.
Exact germination times for Crabgrass will vary from region to region, so if you’re unsure, check in with your local garden store to ask for advice with these weed treatments.
Post Emergent Crabgrass Herbicide
Once Crabgrass has emerged through the Saint Augustine lawn, it will be more difficult to kill, and the more mature the weed gets - it will become far more difficult to kill these weeds properly, if at all. So if we missed out on killing the Crabgrass with a pre-emergent herbicide, then we should get onto treating these weeds as quickly as possible after they are first noticeable.
Specialized post-emergent Crabgrass killers are readily available to treat these weeds, and should be applied as is necessary while the lawn weeds are youngest to effectively treat and kill them from our Saint Augustine grass lawns.