Roadside Revegetation

IMPLEMENTATION GUIDES
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Some seedlings cannot grow through the hydraulic mulch
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Seeds can be damaged by agitators and pumps
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Precocious germination can occur as a result of moisture in the hydraulic mulch
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Hydroseeding requires large quantities of water
With good planning, implementation, and monitoring, many of these limitations can be
managed, resulting in successful revegetation. Ultimately, the success of any hydroseeding
project comes down to the availability of water during germination and seedling establishment.
Hydroseeding is successful in the landscaping business because seeds are irrigated after
hydroseeding until a stand of grass has become established. As one applicator stated, “what
people don’t understand is you can do the best hydroseeding job in the world but if they don’t
water it, it’s not going to grow” (Brzozowski 2004). The challenge in wildland revegetation is
that, for most projects, irrigation is not available. To make hydroseeding successful, strategies
must be developed that maintain moisture around the seeds and in the soil during early plant
establishment.
Integrate Hydroseeding into Revegetation Strategy
From a revegetation standpoint, hydroseeding serves as (1) a method of seed placement, (2) a
means of stabilizing the soil surface for controlling erosion and to allow seedlings to become
established, and (3) a way to apply fertilizers and other soil amendments. These objectives
cannot always be met in one hydroseeding operation. It often requires that each objective be
considered independently, and then integrated into an overall strategy. Clarifying objectives,
based on the site specific conditions of the project, and determining the best way to achieve
them using hydroseeding equipment as part of the approach, will lead to the best revegetation
results. For example, seed placement and fertilizing are different objectives, yet meeting
both objectives is often accomplished in one hydroseeding operation out of convenience.
However, the best time to apply fertilizers on many projects is after the seeds have germinated
(see Section 10.1.1, Fertilizers). Instead of meeting fertilizer and seeding objectives in one
hydroseeding operation, separating them into two different applications would be a better
strategy for meeting overall project objectives.
On a site with high surface rock, for example, the main objective would be seed placement.
Little importance would be placed on surface stabilization since the rock has already created
a stable surface. The best potential sites for seedling germination on this harsh surface would
be between the surface coarse fragments, where seeds are protected and moisture collects.
Yet a common mistake that occurs in many hydroseeding projects is to include the same rates
of tackifiers as would be used on a soil surface. Under these circumstances, tackifiers adhere
seeds to the rock surface, preventing the seeds from washing between the gravel and cobbles
that cover the surface. The objective of stabilizing the surface is not only unnecessary in this
example, it would negatively affect placement of seeds.
Hydroseeding should always be accomplished within a strategy of creating an optimum seed
environment. The hydroseeding operation places seeds on the surface of the soil which is
often a poor environment for germination. Hydraulic mulch is inferior to long-fiber mulches in
reducing surface temperatures, maintaining soil moisture, and moderating surface temperatures
(see Section 10.1.3, Mulches). The term “hydraulic mulch” is misleading because most
materials that fall into this category lack many of the important properties associated with
mulches (see Section 10.3.2.5, Select Hydraulic Mulch and Determine Rates). By their nature,
hydraulic mulches are more like a growing medium than mulches because of their capacity to
absorb water (Most hydraulic mulches hold greater than 1,000 times their weight in water).As
a growing medium, hydraulic mulch maintains high moisture around the germinating seeds.
But once the hydraulic mulch dries out, which is often very quickly on dry sites, it no longer
protects the seeds from drying as a mulch would and germination rates are compromised.
Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat
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