Mixing Bahia and St. Augustine, two distinct warm-season grasses, is generally not recommended for a uniform, healthy lawn. Both are popular turf choices in warm, humid climates, but their fundamental differences in growth habits and maintenance requirements create significant conflicts when planted together. Attempting to mix them often results in a patchy, uneven appearance and complicated lawn care strategies. A cohesive lawn is best achieved by selecting a single grass variety that matches the specific conditions of the yard.
Essential Differences in Growth and Appearance
Bahia grass and St. Augustine grass possess completely different biological and aesthetic traits. St. Augustine is known for its coarse, broad-bladed texture and a dense, carpet-like growth habit, typically presenting a rich, dark blue-green color. It spreads primarily through above-ground runners called stolons, creating a thick turf layer.
In contrast, Bahia grass has a finer texture with thinner blades and a lighter, often sparse, green color. Bahia develops an extensive, deep root system, making it highly tolerant of drought and poor, sandy soils. St. Augustine’s shallow stolons make it less tolerant of dry conditions and require more frequent watering to thrive.
The grasses also differ dramatically in their establishment methods and light needs. Bahia is easily established from seed, while St. Augustine is almost exclusively established using sod or plugs because its seeds are often not viable. St. Augustine can tolerate moderate shade, making it ideal for yards with large trees, whereas Bahia grass requires full sun to grow successfully.
The Consequences of Mixing Grass Types
Planting Bahia and St. Augustine together inevitably leads to a non-uniform lawn that is visually distracting. The stark differences in blade width, color, and density create a noticeably patchy appearance, with the thinner, lighter green Bahia contrasting sharply against the lush, dark green St. Augustine. Bahia grass is also prolific with its distinct Y-shaped seed heads, which sprout above the turf and disrupt the lawn’s aesthetic uniformity.
These two grasses will be in constant competition, with the winner determined by microclimates within the yard. St. Augustine tends to dominate in areas that receive regular water and fertilizer, creating a dense barrier that can suppress Bahia growth. Bahia, with its robust roots, will outcompete St. Augustine in poor, un-irrigated, and sandy sections of the lawn. This struggle for resources results in a shifting mosaic of healthy and stressed patches, depending on the environmental conditions.
Mixing the types also complicates maintenance, particularly concerning weed control. Herbicides formulated for weeds in St. Augustine grass may inadvertently damage or kill Bahia grass, and vice versa. For example, some common post-emergent herbicides are safe for St. Augustine but will severely harm the Bahia. Mowing is also complicated because St. Augustine is typically mowed shorter (2.5 to 3 inches) than the taller, more upright Bahia grass (3 to 4 inches).
Selecting the Dominant Grass for Your Yard
Since combining the grasses is impractical, the decision should center on choosing a single type that best suits the yard’s conditions and the homeowner’s maintenance goals. If the yard has moderate shade, receives frequent irrigation, and the owner desires a dense, carpet-like appearance, St. Augustine is the better choice. It creates a lush, highly-valued turf, provided it receives the necessary water and fertilization.
If the property is large, receives full sun, has poor sandy soil, and the owner prioritizes low-maintenance and water conservation, Bahia grass is the more appropriate selection. Bahia is durable, requires less fertilizer and water, and is more resistant to pests, making it a utilitarian turf for difficult conditions.
To transition a mixed lawn to a single type, the undesirable grass must be eliminated first. For example, to establish St. Augustine where Bahia is dominant, the Bahia should be killed, often using a non-selective herbicide like glyphosate, before the St. Augustine sod or plugs are installed. This step prevents competition and ensures the new, single-variety lawn establishes itself successfully.