Roadside Revegetation

IMPLEMENTATION GUIDES
seed source, were grown. For example, a field is being prepared for sowing California fescue
(Festuca californica) from a seed source in the Blue Mountains of northeastern Oregon. The
field had previously grown California fescue from a seedlot collected west of the Cascades.
Since seed from the previous fescue crop would germinate in the same bed, the resulting
crop would include both seedlots. Since the plants from these seedlots would appear almost
identical, it would be impossible to weed out the plants that came from the previous crop.
Even species in the same genera are difficult to distinguish by untrained weeders and cannot
be weeded out of beds.
Fields that previously produced seed from the same or similar appearing species should be
evaluated for the risk of seed contamination from previous seed crops. There are measures
seed producers can take to reduce contamination risks. These include growing non-seed crops
for several years between seed crops, rotating between grass and forb seed production (forb
seed is easy to discern from grass seed), and fumigating between seed crops. These strategies
must be discussed with the seed producers.
Location of Other Seedlots – Equally important to the history of seed production fields, is
the location of adjacent seed crops of the same species. If seedlots of the same species are
being grown close by, the risk of cross-pollination between crops increases and the genetic
integrity of the proposed seed crop would potentially be compromised. There can even
be cross- pollination between similar species. For example, blue wildrye (Elymus glaucus),
bottlebrush squirreltail (Elymus elymoides), and bluebunch wheatgrass (Pseudoroegneria
spicata) are known to cross-pollinate. Talk to a local botanist or geneticist about which species
can potentially cross breed. Seed crops that can cross-pollinate should also be separated by a
minimum isolation distance. Under most circumstances, the isolation distances should be in
accordance with State Certification Standards (certified class). These standards can be found
at the departments of agriculture for each state.
Irrigation System – Many native species must be grown under irrigation to meet the quantities
of seed specified in the contract. Seed producers that have minimal or no irrigation capacity
are often unlikely to meet seed production requirements and time frames. Only those species
that do not require irrigation should be offered to growers lacking irrigation systems.
Culturing Practices – A review of the culturing practices, which include irrigation, fertilization,
disease, and insect control, should be done to determine whether they are appropriate for the
production of the species being grown. Culturing practices are often written up in propagation
protocols that can be found at http://www.nativeplantnetwork.org.
Control Measures for Non-Target Species – Specific attention must be given to how weeds
and other non-crop species will be controlled. Typical measures include (1) the use of herbicides
prior to sowing and after the crop has been established and (2) hand weeding of non-target
species. The most important period of weed control is just prior to seed harvest because of
the importance of eliminating potential non-target seed before seed harvest.
Seed Harvest Methods – Most seed harvests are carried out with specialized equipment
that detaches seed from the stock, separates it from plant and soil debris, and collects it into
storage containers (Figure 10-67). It is important to know the seed harvesting equipment that
will be used for each species and how it will be cleaned between seedlot crops to prevent the
possibility of seed contamination.
Species with indeterminate inflorescences (seeds that ripen on the seed stock all summer
long) must be hand collected more than once in the summer. Periodic seed harvests of these
species must be planned so that the full range of seed can be collected. The seed producer
should address how these species will be harvested to obtain the maximum seed yield.
Seed Cleaning, Packaging, and Labeling – After seed is harvested, it must be dried and
further cleaned. Seeds are air dried (Figure 10-68) or placed in a forced air drying system. Seeds
are then extracted and cleaned. Awns and flower parts are removed and dirt, stems, and other
Figure 10-67 | Seed
harvesting equipment
Seed harvesting equipment varies by
seed producers and species being harvested.
Discuss with the seed producer
how each species will be harvested and
see that equipment is cleaned between
seedlots.
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