St. Augustine grass (Stenotaphrum secundatum) is a popular, dense, warm-season turf known for its broad, dark green blades. Homeowners often become concerned when they observe unusual, stalk-like growths emerging from the uniform leaf canopy. These growths, often mistaken for flowers, are actually the plant’s reproductive structures, known as seed heads. While natural, their frequent appearance in a maintained lawn often signals a need for cultural adjustments.
Identifying the Seed Head Structure
The reproductive structure is a thick spike that pushes up from the main stem of the plant. This spike is distinct from the typical broad leaf blades and often feels coarse or woody to the touch. The actual flowers and developing seeds, or spikelets, are small and partially embedded along the sides of this primary spike, appearing greenish-purple or straw-colored.
These seed heads extend slightly above the turf, making them highly noticeable after mowing and contributing to a ragged appearance. Although the plant is genetically capable of reproduction, the seeds produced by common turfgrass varieties are generally considered sterile or non-viable. Therefore, seeing these seed heads does not typically lead to unwanted seedlings spreading throughout the lawn.
Why St. Augustine Grass Produces Flowers
The primary stimulus for St. Augustine grass to enter its reproductive phase is environmental stress. When the plant senses that its survival is threatened, it triggers a mechanism to reproduce rapidly. This stress response ensures the continuation of its genetics.
One common trigger is inadequate moisture, such as drought or shallow watering practices. The stress of insufficient water signals that conditions are poor for sustained vegetative growth. High heat or poor soil quality are also powerful environmental stressors.
A deficiency in nitrogen also encourages seed head formation. Nitrogen promotes lush leaf growth, so a lack of it signals the plant to divert resources toward reproduction. Close mowing, which removes a significant portion of the leaf surface, can also induce a temporary stress response.
Strategies for Reducing Seed Head Formation
Minimizing seed head production relies on mitigating the environmental stressors that trigger the plant’s survival response. A consistent maintenance program encourages the grass to remain in a vegetative growth state. Proper irrigation is a foundational strategy, focusing on deep and infrequent watering to encourage a robust root system.
Irrigation Practices
When watering, aim to apply about three-quarters of an inch of water in a single session. Allow the top inch or two of soil to dry out between applications. This method trains the roots to grow deeper, making the plant less susceptible to the surface drought stress that causes flowering.
Fertilization
Adjusting fertilization practices is equally important, as nitrogen application strongly suppresses the reproductive cycle. Apply a fertilizer with a high nitrogen content and a balanced ratio, such as a 3-1-2 or 4-1-2 N-P-K blend. Maintaining a steady supply of nitrogen throughout the growing season keeps the grass focused on producing green leaf tissue rather than seed heads.
Mowing and Maintenance
Mowing height also plays a role in plant health, and St. Augustine grass performs best when kept at a height of three to four inches. This higher cut provides insulation for the soil and promotes a denser canopy, which reduces stress. While mowing cannot prevent seed heads from forming, increasing mowing frequency to every five to seven days removes the visible stalks quickly.
For a more advanced approach, a Plant Growth Regulator (PGR) can be applied. This chemically suppresses vertical growth and seed head initiation.