Hydroseeding is a direct seed application method that sprays large concentrations of seed on the land by using a trailer-mounted tank and sprayer system.The machine sprays out a slurry of seeds and water and sometimes (but not always) mulch and fertilizer. The sprayer is used to apply seed in a manner that minimizes the potential for movement of seeds from the site. This method is commonly used to quickly revegetate roadside excavation sites using conservation mix and grass seed.
Although it is a more common use, this method isn’t limited to herbaceous plant seeds such as grasses. Over the last 4 years, NorthWoods has partnered with Vermont Fish and Wildlife, the U.S. Fish and Wildlife Service, the Intervale Conservation Nursery, The Nature Conservancy, and the Connecticut River Conservancy to experiment with the use of this method with native tree and shrub seeds to restore riparian buffer zones throughout the state. Seed collection efforts by the NorthWoods Riparian Lands team have provided over 450 gallons of seed over the past two years to be used for these projects.
Our project sites are located on abandoned agricultural hayfields filled with invasive reed canary grass. For hydroseeding to be successful, extensive site preparation is needed. This begins by cutting down the grasses and plowing the soil of the project area. After a few weeks, to allow some limited regeneration, herbicide is applied to the site to get rid of any unwanted species, especially the reed canary grass, which tends to take over sites and exclude other species from getting established. Seeding can be done following this treatment or in the spring of the following year, as long as the soil remains relatively bare.
Hydroseeding for riparian restoration allows a high density and even distribution of seed application, which can increase the chances of successful riparian buffer establishment. For the amount of seed broadcasted, it can be more efficient than tree planting, making it particularly useful for larger-scale projects. It also has the benefit of creating an environment where trees can grow up in a more forest-like environment rather than establishing individual shade trees and relying on natural recruitment to turn a buffer of tree islands into a functional forest.
While hydroseeding reduces the effort during seed broadcasting, the time and effort needed to collect, store, and process seeds must be considered to determine the overall effort of the project. Hydroseeding also requires a lot of water, which must either be trucked in or siphoned on-site. Additionally, hydroseeding places seeds on top of the soil, leaving them vulnerable to desiccation, making the timing of seeding, mulching, irrigation, or otherwise mitigating desiccation very important.
Many factors must be considered to ensure successful application, including size of seeds, species selection, and the potential for seed desiccation after they are sprayed onto the bare soil. Clogs in the nozzle can occur if a seed is too large, resulting in extra maintenance time. Species that are more prolific can be useful to outcompete non-target species that may colonize the site. Native species that match site conditions tend to have the best chance of success in restoration sites because they have co-evolved with other species present on the site and also are adapted to the local climate.
NorthWoods has been and continues to be a part of five hydroseeding projects throughout the Northeast Kingdom and Champlain Valley of Vermont. This season the 2023 Riparian Lands Crew from NorthWoods will be continuing this work alongside project partners to collect seeds, refine application methods, and hopefully restore several acres of floodplain forest.
Pictured: Hydroseeding in 2019 at the Hubbardton River Clay Plain Forest in Benson VT.