Overseeding St. Augustine Grass – Everything You Need to Know

St. Augustine (Stenotaphrum secundatum), commonly known as Charleston grass, is a dense, warm-season grass that aggressively spreads to make a thicker lawn. Sometimes pests such as chinch bugs, white grubs, or gray leaf spots attack your yard and make it unhealthy.

Similarly, if the grass faces drought, heavy traffic, freeze, or excess heat, the chances of bald patches and grass thinning increase. Thus, do not let the lawn suffer as it can benefit from overseeing to revive your lawn.

If you want to overseed St. Augustine grass, don’t go without a solid plan. First, understand the basics behind overseeding so you may know what suits your zone’s climatic conditions and what not.

  1. Remember, St. Augustine grass lawns are made with commercially available Augustine sods, plugs, or springs. St. Augustine does not give viable seeds to start a lawn. So, the first option is to buy or dig plugs from established areas and plant in the bare spots. Second, if you want to overseed, go for other warm-season grass varieties such as Bermuda grass. The choice is yours!
  2. When overseeding is locked as your preferred choice, check your lawn’s compatibility with Bermuda grass. St. Augustine is one of the most shade tolerant turfs, while Bermuda goes well in full sun. Testing a bare spot for overseeding is good and indicates how Bermuda seeds respond to your land. You can also remove a 3 feet square section of St. Augustine and seed Bermuda grass as you plant a newly seeded yard.
  3. Last but not least, make sure the lawn is free from weed killers. A pre-emergent is a weed control chemical applied in late summer or early fall to discourage weed spread through winter. These weed killers can hinder seed germination and sprouting, so ensure no weed treatment before overseeding St. Augustine grass.

How to Overseed St. Augustine Grass with Bermuda Turf – Step-by-Step

img source: pexels.com

Growing Bermuda grass in St. Augustine lawn again shows two routes. You can either grow seeds with existing grass and have a mixture or remove St. Augustine completely and transform the yard from St. Augustine to Bermuda lawn. Both ways are practicable and give results if done accurately. So, get both procedures and find the most suitable as per your convenience.

Mixing Bermuda Grass with St. Augustine

Mixing Bermuda grass with St. Augustine is preferable if you live in USDA Zones 7 through 10. Next, follow these steps carefully and get a healthy lawn.

Scalp the Lawn

Set the mower on its lowest settings and mow as short as possible or keep it down to 0.5 inches. By scalping the lawn, you expose the soil to the sun and the incidence of adequate sunlight reaching Bermuda seedlings increases. Leaving taller grass blades of St. Augustine will stop Bermuda seeds from growing.

Rake Well

No rake well with a metal rake to collect debris, stones, and sticks. You may leave grass stubble to support growing seeds; otherwise, the lawn must be clear.

Overseed with Bermuda

Follow the instructions on the seed bag and take 1 ½ pound seeds as per 1000 square feet. Fill a mechanical or hand spreader with Bermuda seeds and move the seeder back and forth across the lawn area for an even spread. If covering a small grass area, use a hand spreader, but a mechanical spreader proves beneficial for large lawns.

img source: pexels.com

Care Routine

Rake the new seeds into the soil and cover them with 1/8 of soil to keep it in place and encourage roots growth. Ensure moisture with regular watering as if it dries out, up to 30% of seeds can die. So, water regularly for two weeks unless grass seeds germinate. Similarly, use the best fertilizer for St Augustine grass, having high nitrogen and little or no phosphorous. Check lawnandpetal.com for more information. For example, 16-0-8 fertilizer is nitrogen-rich, phosphorous deficient, and contains a small amount of potassium.

Properly Mow the Lawn

Mowing an overseeded lawn keeps grass uniform in all areas. St. Augustine performs well when mowed at 3 to 3.5 inches in height, while Bermuda is a low-growing grass and should be cut at 1.5 to 2 inches in height. But for now, Bermuda is grown in the St. Augustine lawn; continue to grow your lawn at 1.5 inches to give Bermuda grass adequate sunlight.

Transforming St. Augustine Lawn to Bermuda Turf

Bermuda grass is efficient enough to take over St. Augustine for its invasive growth habit. Bermuda spreads through two methods; through root system means rhizomes and through runners means stolon. On the contrary, St. Augustine only spreads via aboveground runners that make its growth slow. So, ideal conditions encourage Bermuda to spread and choke out St. Augustine.

Follow these steps to transform St. Augustine lawn to Bermuda turf:

img source: pexels.com
  • Remove existing St. Augustine turf completely by cutting sod with a sod cutter. This helps to eliminate previous grass, thatch layer, and roots in a single step and gives a clean land for overseeding Bermuda.
  • Some home gardeners also use glyphosate-based weed killers, but it may leave the spongy bed of dead grass and harmful chemicals that are unfavorable for Bermuda seedlings. So, you can either skip this option.
  • If there are grass clippings or other undesirable objects, just remove them all before spreading seeds.
  • After clearing the surface, take seeds in the spreader and follow the same steps mentioned in the above method.

Tips and Warnings

  • Augustine’s growth slows down over 5 to 6 years, so overseeding keeps the lawn thick and lush after a particular time.
  • If there is only a small damaged patch in the lawn, e.g., less than 1 foot in size, don’t panic. St. Augustine will fill in these spots over the next month or so when left untreated.
  • Maintaining adequate moisture and Hydro-mulch greatly helps the seeds from drying out between irrigation.
  • Don’t overwater lawn as neither St. Augustine nor Bermuda prefers heavy watering. Instead, waterlogged soil causes fungal diseases and destroys root growth.
  • Installing an aboveground irrigation system with a timer can help avoid overwatering. Set watering as per ground requirement and achieve a steady water plan.
  • When the seedlings are about an inch tall, begin watering once per day, giving about ¼ inch of water each time. Try to avoid runoff and erosion, and water as fast as the soil absorbs.