Roadside Revegetation

IMPLEMENTATION GUIDES
Project Name – The highway or revegetation project name is usually abbreviated.
Collection Year – The year in which the seeds were collected is abbreviated.
Certification – Certification codes apply to conifer tree species and are used to differentiate
what is known about the parentage of the seeds. For example, codes pertain to whether the
seeds were collected from the wild, seed collection areas, seed orchards, or if seeds are from
tested material.
For example, the seedlot code, ARNE-10-502-2030-Elk-04, identifies a pinemat manzanita
(Arctostaphylos nevadensis) seed source, collected on the Rogue River National Forest in seed
zone 502 in an elevation range of 2,000 to 3,000 ft. Seeds were collected for the Elk Creek
Road project in 2004.
Clean and Test Seeds
Wild seed collections must be cleaned to a standard that can be uniformly applied through
seed sowing equipment for seedling production or seed increase. Seed extractories have
the experience and equipment to clean wild seeds of most species. Seed cleaning is typically
completed in two to three steps: (1) removing seeds from cones or seedpods (conifer species
and some hardwood tree and shrub species), (2) detaching structures from seeds, and (3)
removing all non-seed materials from collections. Removing seeds from most conifer cones
involves using tumbling equipment to allow seeds to separate from scales. Some conifer
species and many shrub and hardwood species require specialized equipment to break open
the seedpod without damaging the seeds. Detaching seed structures involves the mechanical
removal of awns (grasses), wings (conifers), and fleshy structures (shrubs). Once seed structures
are detached, all non-seed materials, including stems and chaff, can be removed from the
collections, leaving only pure seeds. Seed extractories will dry, package, and store seeds, as well
as test seeds on- site or send seeds to a testing facility. It must be noted that seed extractories
cannot improve a poorly collected seedlot. For example, seed extractories cannot remove weed
seeds, damaged seeds, or immature seeds from a collection, nor separate seeds from different
crop species mixed in a seedlot. Prior to collecting wild seeds, it is important to contact the
seed extractory manager to discuss which species will be cleaned. Seed extractory managers
are great sources of information on collection and care of a variety of native species seeds.
Cleaned seeds should be tested for germination, purity, seeds per pound, and presence of
noxious weeds (Inset 10-12) by an approved seed testing laboratory (Inset 10-13). Testing
requires representative samples be collected from each seedlot. Seeds are usually stored in
Inset 10-12 | Seed tests
(modified from Tanaka 1984)
Seed testing is used to evaluate seedlot quality and provide information
for determining sowing rates for seed and seedling production.
Methods used for seed testing are based on rules of the Association
of Official Seed Analysts (AOSA). A number of tests are normally
conducted on each seedlot to evaluate physical and biological seed
characteristics.
Physical Characteristics
Purity. Purity tests are used to determine the percentage by weight
of four components: (1) pure seeds of the desired species, (2) seeds
of other species, (3) weed seeds, and (4) inert matter, such as stems,
chaff, scales, and small stones. Graminoid seeds with more than 10
percent to 15 percent inert matter will be difficult to apply through a
rotary seeder or rangeland drill. Purity tests should verify the seedlot
contains no “prohibited” noxious weed seeds and meets or exceeds
standards for “restricted” or “other weed seeds” according to state
standards for Certified Seed. Because each state has different lists of
prohibited and restricted noxious weeds, it is important to request an
“All-States Noxious Weed Exam.” While not prohibited or restricted by
the State, some aggressive non-natives found through seed testing
may still pose a threat to native plant communities.
Moisture content. Seed moisture content for most species is determined
by oven-drying. Seed samples are weighed and heated
at 105 degrees C (221 degrees F) for 16 hours, then weighed again.
Seed moisture is expressed as the percentage of the weight of the
water lost over oven-dry weight. Electronic moisture meters are also
frequently used, but are not as accurate as the oven-drying method.
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