St. Augustine has the best shade tolerance of any warm-season grass. So, if you live in the southern United States like Texas or Florida, or any other subtropical region and have a shady yard, your best best for a full lawn is a shade-tolerant strain of St. Augustine grass, such as CitraBlue or Palmetto St. Augustine.
However, St. Augustine grown in shady areas needs special care. It should be mowed higher than grass in sunny parts of your lawn, watered less, treated with a low-nitrogen fertilizer, frequently weeded, and traffic on shaded grass should be minimized to reduce damage.
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How Many Hours of Sunlight Does St. Augustine Grass Need?
4 hours of direct sunlight per day is the minimum required for the most shade-tolerant strains of St. Augustine grass. Most strains perform best with 6–8 hours of sunlight.
If your lawn doesn’t receive at least 4 hours of sunlight, St. Augustine and other grasses won’t grow there. In shaded areas, consider using an alternative ground cover, such as mulch, gravel, or plants like ivy and Lily of the Valley instead of grass.
How Do You Grow St. Augustine Grass in the Shade?
Just because St. Augustine is more tolerant of shade than other grasses, doesn’t mean it thrives in shaded areas. It’s important to note, there are different types of shade as well:
- Complete Shade: Cast by a solid object such as a building or wall. Blocks sunlight totally. St. Augustine will struggle here unless it receives at least 4 hours of direct sunlight per day.
- Partial Shade: Cast by trees, bushes, and slat fences. This allows some sunlight to filter through. St. Augustine can perform well here if it receives 4 hours of direct sunlight or 6–8 hours of partial sunlight.
In heavy shade, St. Augustine has a tendency to grow thinly or die back. In order to combat this, follow the tips below to ensure lush growth even in shaded areas.
4 inches is the optimal mowing height for St. Augustine grown in shady areas of your lawn. If your grass is thin and struggling at this height, you can even raise your mowing height up to 5 inches.
In sunny portions of your lawn, 3–3.5 inches is ideal for St. Augustine. In shady portions of your lawn, your grass needs extra grass blade surface area in order to capture the smaller amounts of sunlight for photosynthesis. Mowing high is important to keeping shaded St. Augustine healthy.
Shady conditions are cooler and subject to less water evaporation, meaning St. Augustine growing there needs less water. Shaded St. Augustine if often subject to overwatering. If any of the following signs are present, reduce the duration of your twice-weekly watering sessions by 15–20 minutes:
- Soil is soggy or squishes underfoot several hours after you’ve finished watering.
- Grass blades are yellowed.
- Weeds are taking over. Chickweed in particular loves to invade shady, overwatered portions of the yard.
If your St. Augustine is overwatered in the shade, it can develop fungal diseases such as gray leaf spot. Monitor the soil under shade trees and other areas to maintain a healthy lawn.
Use a Gentle Fertilizer
Because shaded St. Augustine grows much more slowly, it requires smaller amounts of nitrogen than areas of the yard that receive direct sunlight. St. Augustine grown in low sunlight conditions also craves potassium, to help increase disease resistance and resist fungal infection.
This slow-release nitrogen fertilizer is perfect for shaded St. Augustine. Apply at product label rates 4–6 times throughout the growing season to promote growth. This gentle fertilizer boosts growth without burning grass or weakening your lawn through nitrogen overload.
Watch for Weeds
Many species of weeds thrive in shade. Whether they’re sprouting along a garden wall or between tree roots, invasive weeds can steal nutrients and sunlight from your St. Augustine. If left unchecked for a growing season, weeds can crowd out your grass.
Use a pre-emergent herbicide in spring to stop weeds, or attack weeds quickly as they sprout. If choked out by weeds, it can take a long time for St. Augustine to recover and fill in areas because it grows more slowly in shade.
Reduce Stress on Your Grass
St. Augustine’s biggest weakness is that it does not tolerate heavy traffic well. If it is shaded under a canopy of trees, it handles foot traffic even more poorly. Moderate use can destroy blades and runners, causing shaded grass to die back.
Where possible, limit foot traffic and your pets’ usage of shaded St. Augustine. Grass burned by your pet’s urine will recover more slowly in shade.
What is the Most Shade Tolerant St. Augustine Grass?
CitraBlue and Palmetto are the strains of St. Augustine best suited for shady lawns. Floratam, a common strain of St. Augustine, does not flourish in shade and should only be planted in sunny lawns.
It’s good to note that even sun-dependent strains of St. Augustine have moderate shade tolerance and often do better in light or partial shade than other warm-season grasses, such as Bermuda and Centipede grass. In short, the least shade-tolerant St. Augustine still grows better in the shade than other grass species.
Is St. Augustine or Bermuda Grass Better for Shaded Areas?
Bermuda grass is far less shade tolerant than St. Agustine. Bermuda will not creep into shady areas and will die back if planted under trees or near shade-casting buildings. If you have a shady yard in a warm region, St. Augustine is your best option for a beautiful lawn.
You will have much better luck attempting to cultivate St. Augustine in low sunlight conditions than replanting or even overseeding with Bermuda. If your St. Augustine is still struggling in the shade despite your best efforts, consider trimming trees to allow more sunlight, or replacing turf grass with ground cover that grows in shade.
What Can You Put Where Your St. Augustine Grass Won’t Grow?
There are several plants that will thrive in shaded areas where grass won’t grow. If you simply cannot get your St. Augustine to perform in shadowed portions of your yard, consider one of the following options instead:
- Carpet Bugleweed
- Mondo grass
- Lily of the Valley
- Japanese pachysandra
- Sweet Woodruff
Each of these plants has much lower sun requirements than any species of turfgrass, making them excellent for shaded areas at the base of trees or alongside homes and buildings. Additionally, all can be cultivated and maintained easily, to create a beautiful and hassle-free yard.
Does St. Augustine Grass Like Sun or Shade?
Grasses are by nature sun-loving plants. St. Augustine thrives in sunny yards, but what makes it unique is that it grows better in shade than any other warm-season turfgrasses.
Where possible, plant St. Augustine where sunlight conditions allow for at least 4 hours of direct sun, or 6–8 hours of dappled or partial sun exposure. Anything less than that, and no grass will grow. For a lush lawn, even in shady conditions, do the following for your St. Augustine:
- Mow at a height of 4–5 inches.
- Water shady areas less, to prevent overwatering and disease.
- Fertilize with a slow-release fertilizer with potassium.
- Control weeds to prevent them from crowding out grass.
- Limit foot traffic on the grass.
By following these simple rules, you can cause St. Augustine to thrive in shaded conditions, creating a lush lawn, even where it doesn’t receive direct sun all throughout the day.