St. Augustine grass is a warm-season grass known for its lush growth and vibrant green color.
St. Augustine grass tends to spread very quickly in warm climates with proper care compared to other grass species.
Colder temperatures and waterlogged soil halt St. Augustine grass growth, so it is essential to maintain ideal conditions for a thick and healthy lawn.
The growth rate of your St. Augustine grass depends on factors such as temperature, sunlight, moisture, and nutrients.
Once St. Augustine grass becomes established, it can withstand heavy foot traffic.
Read on for 11 tips to make your St. Augustine grass spread quickly and grow thicker for a beautiful, lush lawn.
Table of Contents
Soil Preparation
St. Augustine grass grows best in well-draining sandy soil with a pH between 5.0 to 8.5.
A more acidic soil pH will create a thick and lush lawn.
Topdressing your lawn with a sandy loam soil mixture will provide better drainage and aeration for faster growth.
If the soil type is too alkaline with a pH higher than 7.5, your St. Augustine grass will appear yellow instead of having its typical blue-green color.
When the soil is compacted or has poor drainage, you will need to aerate and amend the soil if you want your St. Augustine grass to grow healthy and full.
Plant In Early Summer
Establishing your St. Augustine grass in the early summer when the temperatures are warmer will ensure your grass spreads quickly.
Ideal temperatures for rapid growth in St. Augustine grass range between 80-100° degrees Fahrenheit (38° C).
Low temperatures in late fall will cause stunted growth, and the grass will not spread easily.
Planting St. Augustine grass too late in the season will leave you with thin grass growth and bare spots on your lawn.
If temperatures are warm enough, you may still be able to have a thick, fast-growing St. Augustine lawn in late spring, but early summer is still the ideal planting time.
For more info on planting time, check out our detailed guide on the best time to plant St. Augustine grass.
Apply The Right Fertilizer
Applying a starter fertilizer high in phosphorus will encourage rapid root growth and grass establishment if it is done directly after planting St. Augustine plugs or installing sod.
For best results, continue to use the high-phosphorus starter fertilizer for at least two months before changing to a slow-release fertilizer high in nitrogen.
The high-nitrogen fertilizer will continue to support St. Augustine grass growth by encouraging grass shoots to multiply.
A high nitrogen content will also help the grass runners spread more easily.
As a general rule, you will use one pound of nitrogen-rich fertilizer for every 1,000′ square feet of St. Augustine grass.
The slow-release nitrogen fertilizer is applied once every ten weeks to maintain a rapid growth rate and faster spread.
Properly Water the Grass
While St. Augustine grass is drought-tolerant, it will grow and spread faster when given the proper amount of water.
St. Augustine plugs, or grass sods need to be watered right after installation to jump-start the growth process.
If the weather is extremely hot, lightly water the new lawn twice a day for the first 14 days, so the grass grows thicker and establishes a robust root system.
After your St. Augustine grass has established solid roots and the runners have begun to spread, you will only need to rinse from 1/2″ inch to 3/4″ inch of water twice per week.
Your St. Augustine grass will begin to go dormant or possibly die without a watering schedule of at least 1.5″ inches of water every week.
You also need to be careful not to overwater your lawn.
Waterlogged soil will cause your St. Augustine grass to grow more slowly, and it will require a lot of effort to remove the excess moisture from your entire lawn.
Eliminate Weeds
If you planted your St. Augustine plugs too far apart or left gaps in between the sod, your lawn will be more prone to having weeds.
Grassy and broadleaf weeds will start growing in the spring, and they will deprive your St. Augustine grass of essential nutrients and moisture.
Your grass will grow very slowly without enough nutrients, and the coverage will be thin.
You will either need to use a pre-emergent herbicide before the weeds emerge or a mild weed killer after the weeds have sprouted.
Always read the label on your herbicide of choice to ensure it is safe to use on your St. Augustine lawn.
You may also apply a pre-emergent herbicide at least five weeks for installing St. Augustine sod to encourage faster growth and spreading.
Be sure to wait until temperatures are warm enough for planting your new lawn so your grass can spread quickly and inhibit weed growth.
You may need to use a specially formulated herbicide to get rid of crabgrass, which grows from early spring to throughout the summer.
We have a post dedicated to getting rid of crabgrass if you want to learn more.
Eliminating weeds before they take over your lawn will ensure your St. Augustine grass grows thick and spreads quickly.
Never apply a weed killer to your lawn if the temperature is higher than 85° degrees Fahrenheit (29° C), as this will cause damage to your grass.
Maintain A Tall Mowing Height
The ideal mowing height for St. Augustine grass is between 3-4″ inches.
The one-third rule by only cutting one-third of the grass blade length in each mowing session will encourage the grass to grow and spread.
St. Augustine grass spreads through above-ground stems known as stolons, making the grass more susceptible to damage when cut too short or scalped.
A drought-stressed lawn will grow more slowly, especially during the hottest days of summer.
It can counteract this slow growth by watering your lawn more frequently and mowing less often than the standard 5-7 days.
By slowing down the mowing frequency and increasing the amount of moisture your lawn receives, your St. Augustine grass will start growing thick and full once again.
Do not cut your St. Augustine grass for the first time until it has grown to at least 3″ inches tall.
Remove Pests
Chinch bugs are the most common pests found in St. Augustine lawns because they thrive in a warm, moist climate.
These pests will stunt the growth of your grass and prevent it from spreading rapidly.
Signs of a chinch bug infestation mimic drought damage, and you will notice irregularly-shaped brown spots on your lawn.
Chinch bugs are visible to the naked eye, and if you see them on your lawn, you will have to use an insecticide to get rid of them.
To prevent a chinch bug infestation in St. Augustine grass, it is important to remove any excess thatch from your lawn.
Removing thatch buildup gets rid of the chinch bug’s ideal environment.
Avoid excess thatch by removing lawn clippings after mowing, being careful not to use too much fertilizer, and not overwatering.
Removing thatch by aeration or vertical mowing needs to be done very carefully because it will temporarily slow the spread of your St. Augustine grass.
These methods should only be used when your lawn is entirely healthy so it can recover very quickly.
Prevent Disease
Grey leaf spot is a fungal disease commonly found in hot and moist climates like Florida and other Gulf coast states.
The fungus is also likely to occur when a lawn has been overwatered during the warmest months.
Grey leaf spot prevents St. Augustine grass from growing or spreading very quickly, and the fungus is spread through tiny spores.
Signs of the fungus start as small gray spots on the blades of grass, and once the disease progresses, it will eventually discolor the entire blade.
Once this fungus has spread on your lawn, you will have to apply an appropriate fungicide to get rid of it.
Another common disease in St. Augustine lawns is caused by the Panicum mosaic virus, more commonly known as St. Augustine’s Decline.
This virus is typically found in Texas and surrounding areas.
Signs of the virus include light spots and discoloration on the grass blades, and your lawn will be more prone to damage from drought.
If the disease is not properly treated, it will kill your lawn within three years.
The virus may be treated using an iron-rich fertilizer, but it is best to prevent the disease entirely by choosing a more resistant strain of St. Augustine grass.
Regularly Aerate the Lawn
Regularly aerating your lawn twice per year will help keep your soil from becoming compacted, and it will be able to supply your St. Augustine grass with the nutrients and water it needs to healthy growth.
Compacted soil does not allow the grass roots to spread, and it causes drainage issues.
Excess water makes your lawn more susceptible to a fungal overgrowth and causes the soil to erode.
Core aeration removes plugs of soil to allow nutrients, oxygen, and water to reach the grass roots for healthy root development.
Proper lawn care, nutrition, and moisture create a robust root system and keep your St. Augustine grass growing thick and healthy.
Monitor Dogs On Your Lawn
While a small number of dog feces or urine will act as a natural fertilizer to your lawn, it is best to keep dogs away from your St. Augustine grass as much as possible.
If you have dogs, monitor their bathroom habits to ensure they are not repeatedly urinating or defecating in the same area, causing an excess buildup of harmful toxins.
Too many of these toxins will stunt your St. Augustine grass’s growth and overall spread.
It is also wise to keep your neighbor’s dogs off of your lawn as well, whenever possible.
Keeping other dogs away from your yard may prove to be challenging and expensive, as you may need to build a fence around your yard to remedy the situation completely.
If your neighbor is constantly allowing their dog to urinate or defecate on your lawn, it is best to have a calm conversation with them to explain the problems you are having with this arrangement.
It is always best to resolve the situation calmly before resorting to more extreme measures such as calling your local animal control authorities.
Never doing anything to cause harm to a neighbor’s pet, as this is not only inhumane for the animal, but it could land you in serious legal trouble as well.
High-Density Plug Planting
To jump-start the growth of your St. Augustine grass plugs, the best method is to use high-density plug planting.
High-density plug planting involves planting your St. Augustine grass plugs in a dense growth pattern, usually with 6-11″ inches between sprigs.
This spacing gives your St. Augustine plugs just enough room to develop a healthy and strong root system.
When the roots of your grass are well-nourished, your grass will experience accelerated growth as well as a rapid spread.
In ideal conditions, such as with proper watering, fertilization, and a warmer climate, your St. Augustine lawn will have thick, green grass in as little as twelve months.
Commonly Asked Questions
How long does it take for St. Augustine grass to spread?
St. Augustine grass plugs will begin to spread within 7-14 days of planting.
Once the grass has an established root system, it will grow and spread very rapidly, especially during warmer months.
Temperatures between 80-100° degrees Fahrenheit (38° C) will accelerate the growth.
Why do St. Augustine runners spread on top of each other?
If St. Augustine runners begin to grow on top of each other instead of spreading out, your lawn may appear thin or have bare spots.
The causes for the runners to spread on top of each other include:
- Cutting your grass too short.
- Overfertilization.
- Using too much pre-emergent herbicide.
This problem usually occurs in the spring, when the grass begins to come out of its dormant state and starts to grow quickly.
A nutrient deficiency will also cause St. Augustine runners to grow erratically instead of attaching to the soil.
When do St. Augustine grass roots grow fast?
St. Augustine grass roots grow the fastest during late spring and early summer.
Applying a phosphorus-rich fertilizer during this time will speed up root growth even further.
St. Augustine root growth does not typically slow down until the days get shorter in the late summer months.
During this time, the grass is preparing for the dormancy period in the colder season ahead, storing nutrients.