Hydroseeding refers to the process of applying a mulch, fertilizer, tackifier (optional), water, and seed slurry on a soil surface to promote grass growth. Hydroseeding is considered an alternative to the process of broadcasting seed and is quite productive in terms of coverage per amount of time and rapid growth rates (ample growth can begin in 5-6 days or even sooner). Hydroseeding on the other hand, is a mulch, water, and tackifier mixture only.
The hydroseed slurry is typically made up of water, mulch (paper and wood fibers or straw), seed, and starter fertilizer.
Hydroseed tanks mix the slurry ingredients by either paddle or jet agitation. If the soil is overly acidic, lime may be added to the slurry. The slurry is typically spread through a hose which is attached to a truck or trailer equipped with a large tank.
Straw mulch (in lieu of paper) tends to be utilized more in summer months when seeds should be protected from excessive sun exposure and when the lingering of moisture within and under the mulch combats hot and dry weather. Straw mulch is also used on sloped ground where erosion might be more of a concern. It also keeps seeds from blowing away or being eaten by birds. Straw mulch can hand placed or be blown in with a blower and will typically also receive a ‘tackifier’ product which essentially weaves a structural web, holding the material together.
A Hydroseed tanker truck with a 2,200 Gallon Tank can commonly cover 23,000-30,000 square foot, or 2,500-3,300 square yards. In public traffic areas to be hydroseed, it is common to remove rocks, bricks, etc from the substrate in excess of 1/2″. Hydroseeding is an activity with success hinging heavily around the weather. Permanent Hydroseeding performs best when applied in moderately warm weather, under ample sunlight, with moderate amounts of rain/watering. Excessive amounts of sun and heat can significantly hinder the proper growth process, so much so that many hydroseeders will choose not to apply permanent seed in the hottest summer months.
It is common for temporary seeding methods to be applied in colder months when it can be expected that permanent seeding methods will not ‘take’ due to unfavorable weather conditions (cold, lack of sunlight, lack of water). Temporary commonly consists of a simple broadcast seed and straw application, where the seed will lie dormant until the environment permits growths. It can be assumed that hydroseeding requires less watering than broadcasting seed or straw mulch seeding methods but it still requires plenty of water and sunlight.
Depending on the project, the area to be sprayed may need preparation work done prior and it is commonly expected in the industry that a hydromulching price include at least minor prep work prior to spraying. This prep work might include placing several inches of topsoil or loosening/raking the soil and removing small stones with a ‘Rock Hound’ or a ‘Harley Rake’ skidsteer attachment or tractor. Then the final grading is typically done by hand raking.
There are different seed mixes specialized for different areas: ex. lawns, rural roadsides, slope mixes, etc. There are also native grass mixtures and wildflower mixtures. Hydromulching provides an excellent stand of grass on rich topsoil. It will come up moderately well on clayey-silty soils if watered adequately. It does not perform particularly well on overly sandy soils (more than 50% sand).
All seed mixtures will have some propensity to produce weeds. Also fresh, rich topsoil while an excellent substrate for grass growth, will also be susceptible to heightened weed growth. Some argue that the use of straw mulch instead of wood fiber can also contribute to weed growth in new grass seed.
A common hydromulch mixture ratio per 1000 square feet is: 20 lbs of fertilizer (liquid or pellet) or enough that 1-lb of nitrogen is present, 5-7 lbs seed, 40-50lbs mulch.