St. Augustine grass is a popular warm-season grass known for its ability to tolerate extreme heat and humidity surprisingly well.
However, it is also very good at dealing with shady conditions, too!
But how well will it grow in shade, and how much sunlight does it actually need to thrive?
We’ve got all the information you need here.
Overall, St. Augustine grass tolerates heat, humidity, and even partial shade quite well. It is among the most shade-tolerant warm-season grasses, with most varieties needing only 4 to 6 hours of sunlight per day.
Follow along to learn everything you need to know about caring for St. Augustine grass, namely how much shade it is able to safely tolerate, how much sunlight it requires, and how to properly maintain it for a beautiful, lush lawn.
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Does St. Augustine Grass Grow in Shade?
In general, St. Augustine grass tolerates shade much better than most other warm-season grasses. Certain variants such as Seville, Palmetto, and Sapphire are especially shade-tolerant, as they only need around five hours of sunlight per day to grow properly.
If you live in a warmer climate, such as in the southeastern United States, and need the right kind of grass to cover a heavily shaded area of your lawn, St. Augustine is an excellent choice.
In addition to its ability to withstand high temperatures and high humidity well, this type of grass also fares particularly well in coastal areas with high amounts of salt in the soil.
Most notably, though, it grows well in shaded spots, such as around buildings and structures and under trees and bushes.
For areas like Florida, Georgia, and the hot and humid southeast in general, St. Augustine is a perfect candidate for various areas of your lawn, whether they’re heavily shaded or under direct sunlight.
Check out our related post on the best time to plant grass seed in Georgia if you live there.
However, to ensure your St. Augustine grass grows properly and maintains its vibrant bluish-green color, you’ll need to take a few extra steps to keep it hydrated and well-fed.
We’ll cover how to maintain this uniquely hardy type of grass in the shade below soon, but first, let’s discuss exactly how much shade it tolerates and the minimum amount of sunlight it needs to thrive.
How Much Shade Can St. Augustine Grass Tolerate?
Most types of St. Augustine grass need only around four or five hours of direct sunlight per day, making it one of the most shade-tolerant warm-season grasses available. Some variants, such as Bitter Blue and Palmetto, are able to thrive on as little as three hours of sun per day.
For partially or even heavily shaded areas, St. Augustine grass is one of the best choices when it comes to warm-season turf grasses.
Virtually all existing strains are able to grow well with less than six hours of direct sunlight per day, and several particularly shade-tolerant varieties will get by on as little as three hours of sun each day.
Any less than this is risky, even for the hardiest strains.
Notably, it is even more shade-tolerant than Zoysia grass, another popular warm-season grass species known for its hardiness in both sunny and shady conditions.
This means St. Augustine grass is able to tolerate up to 16 hours of partial to heavy shade per day, making it possibly the best variety of grass for shaded areas!
How Much Sun Does St. Augustine Grass Need?
Depending on the strain, St. Augustine grass needs around four to seven hours of direct sunlight per day. The most popular type, Floratam, needs around six hours each day, while some of the hardier varieties like Seville, Sapphire, and Bitter Blue need only around three to four hours.
St. Augustine is a popular choice of grass because it is able to tolerate an impressively wide range of conditions for a warm-season variety.
It is surprisingly hardy in high-heat, direct sunlight, and high-humidity conditions, but it tolerates partial and even heavy shade quite well, too.
The exact amount of sunlight St. Augustine grass needs to stay healthy and vibrant varies slightly depending on the strain or type you select.
While its most popular variety, Floratam, needs about six hours of sunlight each day, some of the even more shade-tolerant strains like Seville, Sapphire, Bitter Blue, and Palmetto are able to get by on as little as three to four hours of sunlight each day!
For more tips on getting St. Augustine grass to grow thick, check out our article.
What is the Most Shade-Tolerant Type of St. Augustine Grass?
The most shade-tolerant varieties of St. Augustine grass are Bitter Blue, Palmetto, Sapphire, and Seville. These strains are all able to grow properly in shaded conditions with as little as four hours of sunlight per day.
Not all types of St. Augustine grasses are equally shade tolerant!
The most popular variety needs at least six hours of sunlight each day to thrive, and some other varieties need slightly more.
However, a few notable strains are mentioned above, with Palmetto being potentially the most versatile and the hardiest when it comes to weather conditions and foot traffic.
With plenty of care and maintenance, Palmetto grass is able to subsist on only around four hours of sunlight each day.
How to Maintain St. Augustine Grass in the Shade
It is possible to boost St. Augustine grass’ shade tolerance with the following maintenance tips:
- Mowing at a slightly higher height
- Trimming nearby trees to improve sunlight conditions
- Applying fungicide treatments at least once per season
- Using a 3-1-2 NPK fertilizer every 4 to 8 weeks
While St. Augustine grass is naturally quite shade-tolerant, there’s still plenty you’re able to do to help protect it and boost its growth in shaded areas.
Perhaps the most notable bit of advice here is to simply mow any St. Augustine grass in the shade at a slightly higher height than the rest of the grass in your yard.
This gives the individual grass blades a bit more height and surface area so it is better able to photosynthesize and take in nutrients despite getting less sunlight than the rest of your yard.
We recommend keeping it trimmed to a height of around 2.5” inches on average in the shade and around 2” inches in more sunny areas.
Additionally, while you likely won’t be able to modify any buildings in your yard much, you should at least have the option of trimming any shade trees and shrubs around the grass to at least slightly improve sunlight conditions.
Even an extra half an hour of sunlight is vital to the growth and health of your lawn!
Another important thing to note is any grass grown in moderate shade is automatically going to be more susceptible to lawn and fungal diseases.
This is why it’s a good idea to treat any St. Augustine grass in the shade with a fungicide treatment at least once every season as a form of preventative maintenance for a healthy lawn.
Finally, be sure to give your lawn in the shade a bit of extra TLC in the form of fertilizer every month or two.
The exact type of fertilizer needed will potentially vary slightly depending on your soil quality, but as a general rule, a 3-1-2 ratio NPK fertilizer or anything fairly high in nitrogen is a good choice.
Make sure you know when the best time to plant St. Augustine grass is to give it its best shot at life.
How Short Should You Mow St. Augustine Grass?
St. Augustine grass fares best when kept at a slightly higher height than the rest of your lawn. For grass in the sun, a height of around 2” inches is recommended. For grass in heavily shaded areas, keep it a bit higher at around 2.5” inches.
Overall, St. Augustine is a type of grass which does not do well with being kept very short.
“Scalping” or mowing too low is a common issue with this variety of lawn grass because it needs extra height to be able to take in the additional sunlight, water, and nutrients necessary to protect itself in partial to complete shade.
If you’re wanting a lawn you’ll be able to keep at a neat and uniform 1” inch at all times, St. Augustine is definitely far from the best option.
In fact, virtually any shade-tolerant grasses must be kept at a slightly higher mowing height than average.
While many kinds of grass do just fine at heights of 1” inches or even less, even red fescue, another popular shade-tolerant grass type, needs to be kept at around 2” inches or higher.
Essentially, the added height not only gives your lawn an added nutrient supply to pull from, it makes it easier for the individual grass blades to photosynthesize and pull in sunlight.
The extra surface area and height are extremely valuable for grasses like St. Augustine.
How Often Should You Water St. Augustine Grass?
Like most shade-tolerant grasses, St. Augustine needs very little water, or around only ½” inches per week to thrive in the shade. Water doesn’t evaporate nearly as quickly in shaded areas, so deep yet infrequent weekly waterings are best.
As a general rule, you should water your St. Augustine grass until you begin to see a small amount of runoff.
Usually, watering for around 5 to 10 minutes is enough, depending on the water pressure you’re working with.
St. Augustine grass is able to thrive with very little water, especially in the shade.
While it needs around 1” inch of water per week in the sun, ½” inches is more than enough every week in partial shade.
The main reason why so little water is necessary for this type of grass’ survival is water isn’t absorbed nearly as quickly in the shade as it would in full sunlight.
This is mostly because your yard is a lot cooler and experiences far less stress from the sun in the shade, so less water is needed to keep it hydrated.
Also, the water also won’t evaporate on the surface of your yard nearly as quickly as it would under full sunlight.
What Kind of Fertilizer is Best For St. Augustine Grass?
Shade-tolerant grasses like St. Augustine do best with fertilizers with a fairly high amount of nitrogen. Either a 3-1-2 or a 4-1-2 NPK ratio is best. Ideally, you should fertilize every 4 to 8 weeks, or every month during the active growing season and every two months during the dormant season.
While any nitrogen-rich fertilizer is recommended for all St. Augustine grass varieties, the ideal ratio is either 3-1-2 or 4-1-2.
This means, for example, a 16-4-8 fertilizer or a 20-5-10 would also be appropriate.
Certain brands list their NPK ratios slightly differently, so pay attention to the label before using them.
Around one pound of nitrogen per 1,000’ square feet is recommended.
In particular, we advise using something like Simple Lawn Solutions’ Advanced 16-4-8 Balanced NPK Lawn Food.
It’s ideal for various types of warm-season grasses, including the more shade-tolerant ones like St. Augustine and all of its many strains.
When it comes to your fertilizing schedule, stick to applying it around once a month during the active growing season in the spring and summer.
During St. Augustine’s dormant period in the fall and winter, fertilizing every two months or so is best.
How Often Should You Aerate St. Augustine Lawns?
Core aeration and spike aeration are highly recommended to improve your lawn’s soil quality and drainage, especially for shade-tolerant grasses like St. Augustine. For most lawns, aerating every one to two years is best to keep soil from becoming compacted.
All lawns benefit from some degree of aeration, and St. Augustine grass is no different.
There are three main types of aeration: core, spike, and liquid, but core and spike are generally the most effective and cost-efficient.
It’s a good idea to aerate your entire yard at least every year or two to keep your soil healthy and improve drainage, especially in shaded areas.
Core aeration essentially involves using a tool to remove compacted “cores” of soil from your lawn.
Spike aeration requires you to dig small spikes a few inches into the ground to loosen the soil and improve drainage.
Liquid aeration is exactly what it sounds like–applying a liquid chemical product directly to your lawn to loosen the soil.
In addition to aerating your lawn yearly, dethatching regularly will also go a long way in keeping your yard healthy and looking great.
Whenever you notice your thatch layer reaching around ½” to ¾” inches, go ahead and dethatch.
This usually translates to once or twice per season.