Hydroseeding involves spraying a specialized slurry onto the ground to establish vegetation. This mixture combines grass seed, water, fertilizer, and a protective mulch layer, often dyed green, creating an ideal micro-environment for germination. You can hydroseed over an existing lawn; this process is specifically known as overseeding. Success relies on extensive preparation, ensuring the new seeds can reach the soil beneath the existing grass canopy.
Preparing the Existing Lawn for Overseeding
Before applying the hydroseed slurry, the existing lawn requires aggressive preparation to minimize competition and maximize seed-to-soil contact. First, address any broadleaf weeds or undesirable plant species several weeks in advance using an appropriate herbicide. This step is necessary because new grass seedlings cannot successfully compete with established weeds for light, water, and nutrients.
The next action involves “scalping,” which means mowing the existing grass down to its lowest possible setting, typically one inch or less. This reduction in height exposes the soil surface, allowing light and moisture to penetrate the dense turf canopy. It also stuns the old grass slightly, giving emerging seedlings a temporary competitive advantage.
Following the close mow, the lawn should be aggressively dethatched or power-raked to remove the layer of dead organic material, or thatch, that lies above the soil. Core aeration is also highly beneficial, as it pulls small plugs of soil from the ground, significantly reducing compaction and creating pockets for the seed to settle. Without these efforts, the hydroseed mixture would merely sit on top of the thatch, leading to poor germination rates and weak root establishment.
It is advisable to conduct a soil test to check the pH balance and nutrient levels before application. Most turfgrasses thrive in a soil pH range of 6.0 to 7.0. Amendments like lime or sulfur may be tilled into the topsoil if the pH is outside this optimal range. Addressing soil deficiencies beforehand provides the best possible foundation, ensuring new seedlings have immediate access to the necessary minerals for strong initial growth.
The Hydroseeding Application Process
The hydroseeding application for overseeding uses a slurry mixture with slightly modified components compared to planting on bare ground. The mixture contains the chosen grass seed blend, water, a starter fertilizer high in phosphorus, and a protective layer of wood or paper fiber mulch. This mulch is designed to absorb and retain moisture, keeping the seeds continually hydrated during the germination phase.
A tackifier, a glue-like binding agent, is an important ingredient in the overseeding slurry. This additive ensures the mixture adheres securely to the existing short grass blades and exposed soil, preventing wash-off from rain or irrigation. When overseeding, the slurry thickness is often reduced compared to a new-lawn application to avoid suffocating the existing turf beneath heavy mulch.
The high-pressure spray from the hydroseeder ensures a uniform distribution of all materials across the area. This method provides more consistent coverage and a more even growth pattern than traditional broadcast seeding techniques. The mixture creates a moist, nutrient-rich blanket that protects the seeds from wind, birds, and excessive sun exposure, fostering rapid germination.
Post-Application Care and Expected Results
The period immediately following hydroseeding is the most important phase for determining the success of the project. The primary focus of post-application care is maintaining consistent moisture in the hydroseed mulch layer. This requires frequent, light watering sessions—typically two to four times per day for five to fifteen minutes each—to keep the surface moist without creating puddles.
This shallow, frequent watering must continue for the first four to six weeks until the new grass is well-established. If the seedlings are allowed to dry out after they have begun to sprout, they will quickly die. As the grass grows taller, the watering frequency can be gradually reduced, and the duration of each session lengthened to encourage deeper root growth.
Visible germination typically begins within one to three weeks, depending on the seed type and weather conditions. The first mow should be delayed until the grass blades reach a height of approximately three to three and a half inches. When mowing, use a sharp blade and never remove more than one-third of the blade height at one time, which prevents stressing the young turf.
It is recommended to avoid applying weed-control products for the first three months, as the chemicals can severely damage the delicate new seedlings. Overseeding with hydroseed improves the density and health of a thinning lawn, but it is an enhancement rather than a complete overhaul. While it will thicken patchy areas, it will not correct major underlying soil or grading issues.