Killing Weeds in St Augustine Grass

Killing weeds in St Augustine grass before they can get established in large numbers is the best approach. This lawn care guide outlines the best method for controlling weeds throughout the growing season, keeping your lawn as attractive as possible.

Keep your St Augustine Grass Healthy
A healthy lawn is less vulnerable to the encroachment of weeds. Therefore, keep your St Augustine lawn fertilized and watered on a regular basis. We have included specific articles on fertilizing and watering St Augustine grass in this guide. See those articles for all the details. When your lawn is healthy, it may actually crowd out weeds, winning the competition for nutrients, water and oxygen.

Give Weeds a Hand
If there are just a few weeds in your lawn and you’d prefer not to use weed killer unless you have a major weed issue, you may want to pull them by hand. Use a hand trowel on tough weeds to make sure you get them out, root and all. When your lawn is relatively weed-free, this can be an effective method for keeping it that way.

Apply Weed Killer in the Spring
In March of each year, as the St Augustine begins to green up, apply a pre-emergence weed killer. By definition, this type of herbicide stops weeds before they get started. Many homeowners choose the time when the forsythia plants are in bloom to apply pre-emergence herbicide.

Then in May apply a post-emergence weed killer that will eliminate any weeds that have managed to take root in the lawn. These herbicides are primarily designed to get rid of summer annual and perennial broadleaf weeds. Don’t apply post-emergence herbicide until the lawn has been green for 3-4 weeks. If no weeds are present, there’s no need to use week killer until they appear.

Read the labels carefully before applying any week killer to your lawn. Make sure it is safe for use on St Augustine grass. If you know what type of weeds your dealing with, that may also help you find the right product, though most herbicides cover a broad spectrum.

Cut your Grass Regularly
St Augustine grass will look better and grow more uniformly if it is mowed every 7-10 days. Its ideal height is 2” to 3”. In addition, regular mowing will keep weeds from developing seeds and spreading.
It takes a comprehensive approach to keep weeds out of your lawn. When you do, your St Augustine grass will thrive, adding beauty, value and enjoyment to your home’s landscape.