Through a series of laboratory and field experiments, the seed feasibility study has documented the necessary steps involved in using seed to create dense mosaics of native riparian land covers. Steps in the process included, seed collection, storage, treatment, planting, germination, and monitoring seedling growth and survival. Using seeds may be feasible if it involves less labor, is more cost effective, or preserves the genetic diversity of the riparian habitat created under the LCR MSCP. The amount of nonnative to native vegetation resulting from using seed for restoration will also be an important factor in determining the feasibility of this method.

Over four seasons, the techniques to achieve riparian seeding have been refined using information and best practices from the laboratory experiments and through the establishment, monitoring and management of a series of small plot studies. The details of these experimental trials are available on the LCR MSCP website in the technical reports section.  A summary of the results is provided below.

Four years of study on the feasibility of using native seeds for riparian restoration have pointed toward the following conclusions:

• Fremont cottonwood, Goodding’s willow, and coyote willow seed can be stored cleaned or uncleaned in freezers for over two years while retaining viability of greater than 80%.
• The optimal seeding method for Fremont cottonwood and Goodding’s willow is hydroseeding on to furrows.
• Fremont cottonwood and Goodding’s willow should be seeded separately to avoid cottonwood dominance of seeded areas.
• When co-established, Fremont cottonwood dominates volunteer saltcedar.
• Establishment of undesirable species (primarily saltcedar and grasses) can be controlled by reducing the seed bank on and adjacent to revegetation areas and by spraying revegetation areas with grass-specific herbicide during the first growing season.
• Infrequent, deep irrigation appears to enhance survival of Fremont cottonwood and Goodding’s willow compared to frequent, shallow irrigation.
• Large-scale direct seeding of Fremont cottonwood would likely result in cost reductions of over 60% compared to mass transplanting.
• Large-scale direct seeding of Goodding’s willow would likely result in cost reductions of over 40% compared to mass transplanting.

The applicability of seeded for large-scale restoration is still unclear. The results of this study show promise, however a large-scale demonstration of these established techniques and protocols would be prudent to determine the true effort, logistics, and costs involved in establishing riparian cover type in a restoration setting. In addition, long-term monitoring of the experimental plots should be continued to determine if the competitive treads in these experiments will continue and if seeding can produce the desired species composition and habitat characteristics necessary for LCR MSCP covered species.  Additional information can be found in the 2008 Annual Report found at this link.

Updated January 4, 2017