Spring Maintenance Tips for Your St. Augustine Lawn

With the arrival of spring comes colorful, blooming flowers, singing birds and the return of green St. Augustine lawns. For us lawn and garden lovers, this is one of the most exciting times of the year! It’s important to note that seasonal maintenance on lawns slightly differs each season as temperatures and soil conditions change. In the spring, St. Augustine is just starting to come out of dormancy and turn green again. Depending on where you’re located, your St. Augustine may not have even gone dormant at all!

Read on for a list from our turfgrass experts put together on some of the most important maintenance practices for your St. Augustine grass going into the spring season. Be sure to also refer to our St. Augustine Homeowner Maintenance Guides for generic St. Augustine, Palmetto® St. Augustine and CitraBlue® St. Augustine. Each maintenance guide is divided into sections for spring, summer and fall maintenance.

1. Begin Mowing Your Lawn at the Proper Height Again

The timing for which the first mow of the spring for your mature, established St. Augustine widely varies depending on the area you live in. St. Augustine can come out of dormancy differently depending on the environment and temperatures your area encounters. For example, if you live in South Florida, your St. Augustine may have never entered dormancy at all during the winter. Many homeowners who live in South Florida will mow their lawn every other week during the winter—oftentimes starting in September and resuming a regular, weekly mowing schedule again in mid-March.

Generally speaking, mid-March is about the time for you to begin your regimen for spring green-up and mowing. The first mow of the spring shouldn’t take place while your St. Augustine lawn is dormant—wait until it’s actively growing again before mowing and never remove more than a third of the leaf blade.

Keep your St. Augustine between 2–4 inches in height. However, these heights slightly vary for different cultivars of St. Augustine. For example, Palmetto should be maintained at a height of 1.5–2.5 inches whereas CitraBlue should be kept at a height of 2–3 inches during the spring.

Lastly, a good tip for spring is to make sure your lawn mower blades are sharpened so that the mower blades neatly slice through the grass in place of ripping them. If the grass blades aren’t cut neatly, the mower is ripping them and opens the grass up to possibility of disease. Performing regular maintenance on your mower is good practice for the end of the mowing season or before spring takes place.

2. Start Your Lawn Off Right with the Appropriate Spring Fertilizer This Year

With most St. Augustine grass coming out of dormancy, the spring is one of the most important times to use fertilizer. The fertilizer needs to promote healthy roots and the return of green leaf blades.

Be careful when making your first fertilizer application of the year though—it is common for homeowners to see their grass green up and immediately pull out the fertilizer and lawn mower. We advise that you typically wait until the last frost has hit. If you fertilize your lawn and another frost hits, your St. Augustine will go right back into dormancy and you’ll have a harder time getting it to green up again. This does more harm than good.

The date of the last frost varies from location to location. In the Florida Panhandle, for example, St. Augustine may not go dormant and will reach its full green-up in early February (depending on how cold the winter was). Even then, you won’t want to apply fertilizer until after Easter once the last frost has passed. Refer to the Farmer’s Almanac to figure out the last frost date for your area in 2021.

Sod University recommends two different options for St. Augustine spring fertilization: Lawnifi® Foundation, a slow-release granular option that comes in 25 lb. bags and lasts for three months, and our Lawnifi Spring Fertilizer Box, a liquid fertilizer program that includes three bottles of liquid fertilizer that can be applied monthly with a hose-end sprayer. Each option covers 5,000 sq. ft. Learn more in Granular vs. Liquid Fertilizers or by clicking the two products listed below. Our patented nano-fertilizers with Catalyst Technology^TM give your St. Augustine lawn the jump-start it needs to emerge from dormancy, green up fast and thrive throughout the spring months. Read Why Use Lawnifi Fertilizer? for more information about Lawnifi.

Next, it is important to mention that you may start to notice spots of brown or straw-like grass while the rest of your lawn comes out of dormancy. This is usually a sign of disease. You do not want to apply fertilizer to a lawn with disease as the nitrogen in the fertilizer will feed the disease and promote its growth. Apply a systemic fungicide first and then wait several weeks before following with a fertilizer application.

3. Set Up a Spring Irrigation Schedule

Dormant St. Augustine doesn’t need much water until the active growing season kicks in and your grass starts to green up. In our Winter Lawn Maintenance Tips article, we state that if you have a dormant, warm season lawn, it is not dead—it’s just “sleeping”. Although dormant grass requires much less water than it would while it is actively growing, it will still need water. Once it starts to come out of dormancy, St. Augustine requires about 1 inch of water per week including rainfall. The same can be said for the different brands of St. Augustine like Palmetto or CitraBlue. If you aren’t sure how to measure how much water your lawn is receiving, an irrigation audit may be beneficial to you. Irrigation audits provide measurable information about how much water each area of your lawn is receiving within a given amount of time.

If you’re a homeowner who lives far enough south and your St. Augustine doesn’t go dormant during the winter, you may continue to regularly water your lawn in the winter. However if you live in South Florida, for example, you may turn your irrigation off completely during the winter and during the months of June–August when it rains a lot. The atmosphere in South Florida isn’t usually evaporating much water and the grass isn’t using it much during the winter, so frequent irrigation isn’t needed.

The next few tips in this article discuss spring applications for fungicides, herbicides or insecticides. If any of these control products or fertilizers are granular, you will need to water the product in so that your lawn absorbs it. This means that you will already be watering your lawn with the appropriate amount of water during the week of application. The same can be said with any liquid products as they are either products that attach to the end of your garden hose or require tank mixing with water.

4. Control Weeds with a Pre- or Post-Emergent Herbicide

The most important thing you can do for any weed issues your lawn may be having come springtime is to apply a pre-emergent herbicide. A pre-emergent herbicide functions to prevent weeds from emerging from the surface of the soil, as its name suggests. So if you know you get a lot of weeds in the summer like goosegrass or crabgrass, applying a pre-emergent to keep them from even appearing may be a good idea for you. It’ll also save you time, money spent on more product and effort from pulling the weeds that appear in the future. It’s actually not recommended you use an herbicide in the summer or winter, so pre-emergents can be especially useful for this reason. Read more about this in The Best and Worst Times for Herbicide Applications.

Pre-emergents should be applied during the spring when ground temperatures reach about 55 degrees Fahrenheit. The exact dates for these applications differ depending on the area you live in, but generally speaking, pre-emergents should be applied between March 1st and March 15th in the spring. For more information, read our blog on spring pre-emergent applications and refer to our recommended pre-emergent herbicides below. 

Apply post-emergent herbicides in May as needed to control summer annual and perennial broadleaf or grassy weeds like white clover, knotweed, spurge, lespedeza, crabgrass or goosegrass. Atrazine-based post-emergents like the ones below are the most effective control product for St. Augustine lawns. They also serve as an excellent pre-emergent herbicide. Be sure to follow product labels appropriately during application. Lastly, if you notice weeds and you aren’t sure which type of weed it is, check out our Identifying Common Lawn Weeds blog.

Note: St. Augustine and centipede lawns are sensitive to active ingredients like 2,4-D, MSMA or Mecroprop. Apply an Atrazine-based weed control product like Hi-Yield Atrazine or Spectracide Weed Stop For St. Augustine and Centipede to control weeds. Both Atrazine products serve as pre- and post-emergent herbicides.

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Pictured above from left to right: Crabgrass, goosegrass, clover, knotweed, spurge and lespedeza.

5. Watch Out for Insects That May Begin Coming Out

If your lawn has suffered from insect damage around this time in the past, it is a good idea to apply a broad-spectrum insecticide at this time to prevent them from coming back again. If the insecticide is a granular product, be sure to water it in so that it soaks into your soil. On the other hand, if it’s a liquid product, you will either need to attach it to the end of your garden hose or tank mix it. Some of the most common spring insects in St. Augustine are white grub worms and chinch bugs. If you notice yellow spots in your lawn that somewhat resemble drought damage, check for chinch bug activity. You can read more about these insects in our Insect Identification blog. Refer to some of our most popular and effective insect control products below and be sure to follow product label instructions before application.

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Pictured above from left to right: White grub worms and a Southern chinch bug.

6. Prevent Disease as Temperatures Begin to Warm Up

As previously mentioned, circular brown or yellow spots may start to show up as St. Augustine comes out of dormancy. This is a sign of disease and you may need to make applications of a systemic fungicide. St. Augustine is also prone to gray leaf spot, a disease that shows up around this time that looks like little gray/brown spots on St. Augustine leaf blades. Even if you don’t have disease in your lawn, it’s still good practice to apply it preventively to keep disease from taking over—especially if you’ve had disease in the past around this time. Systemic fungicide applications should take place before you apply any spring fertilizer. If you have fungus in your lawn, the nitrogen found in fertilizers oftentimes feeds it and helps it spread. Apply a systemic fungicide and wait a few weeks before applying any fertilizer. Read product labels thoroughly.

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Pictured above from left to right: Spring dead spot and gray leaf spot.

There are a few other optional things that can be done to help your lawn thrive in the spring. Before the onset of summer heat, lawn patchwork and light top dressing with a sand and topsoil mix is a great way to recover any weak areas. Plugs can be purchased to fill in areas of the lawn with bare spots.

Aerating your lawn is also an ideal way to help deliver nutrients and really break up compacted soils. We typically recommend doing this once every couple of years. If you notice thatch that is thicker than 1⁄2 inch, dethatch in late May. Read more in Aerating vs. Dethatching.

Spring maintenance tips differ from other practices that take place during the rest of the year. Weather starts to warm up and everything will turn green again. Be sure to check out our individual Homeowner Maintenance Guides for generic St. Augustine, Palmetto® St. Augustine and CitraBlue® St. Augustine.