Roadside Revegetation

IMPLEMENTATION GUIDES
of the seed increase contract. This section describes
how to calculate the amount of wild seeds to collect
based on the amount of seeds expected from a
nursery seed producer.
The amount of uncleaned wild seeds to collect for
seed propagation contracts requires the following
information (used in calculations in Figure 10-50):
◾◾
Seed needs
◾◾
Years in seed production
◾◾
Sowing rates
◾◾
Annual seed yields
◾ ◾ “Cleaned-to-rough cleaned” seed ratio
Seed Needs – The total seeds needed for each
species on a revegetation project is based on the
total planned revegetation acreage, seedlot characteristics
(germination, purity, seeds per pound), site
limitations (how well seeds will survive), and the desired seedling densities after seeds have
germinated. The reader is referred to Section 10.2.4.3, Determine Seed Needs, for methods to
calculate how many seeds are needed for each species in a revegetation project.
Years in Seed Production – Every species has its own seed production characteristics. For
instance, species such as blue wildrye (Elymus glaucus) and California brome (Bromus carinatus)
produce high seed quantities the first and second year, then level off or decline in years three
and four. Species such as fescues (Festuca spp.) and Junegrass (Koeleria spp.) yield few seeds
in the first year, but seed harvest levels increase to full production in the second or third year.
For these species, a minimum of two years must be scheduled for seed production. Section
10.2.4.3, Determine Seed Needs, shows first- and second-year yields for some commonly
produced species.
Since seeds can be stored for many years, seed production does not have to occur all in one
year. For projects that have several years lead time, maintaining production fields gives the
revegetation specialist more flexibility. By spreading the seed production over several years,
the acreage in production and the amount of wild seed to collect can be cut in half. For
example, if 800 lb California brome (Bromus carinatus) seeds for a revegetation project are
needed and there are two production years to produce it in, the amount of seeds to produce
per year would be 400 lb. Since half the acreage would be sown, the amount of wild seed to
collect would be cut in half, from 10 pounds to 5 pounds.
Sowing Rates – All growers require a minimum amount of clean, wild seeds to produce a
given quantity of nursery-grown seeds. While these rates differ somewhat between seed
producers, general sowing rates for commonly propagated species are shown in Table 10-14
in Section 10.2.4, Nursery Seed Production.
Annual Seed Production Yields – The amount of seeds that are produced annually varies
by species, geographic location of the fields, weather conditions, and experience of the seed
producer. Knowing what yields can be expected from seed producers will determine how
many acres will be under production and the amount of wild seeds needed to start the crop.
Average seed yields for some species are presented in Table 10-14 in Section 10.2.4, Nursery
Seed Production.
Cleaned-to-Rough Cleaned Seed Ratio – Seed collection from the wild will include stems,
chaff, and flower parts (Figure 10-51). This material should be cleaned as much as possible by
the seed collectors before it is sent to the seed extractory for final cleaning. The amount of
non- seed collected can be a substantial part of the wild seed collection weight. “Cleaned to
A Seed production needs 22 lbs From seed needs plan (See Section 10.2.4.3)
B Years in production 2 yrs
C Sowing rates 1 lbs/ac
D Annual seed yields 50 lbs/ac/yr
E (A/B) / D 0.22 ac Area seed producer needs to sow
F E * C = 0.22 lbs
“Cleaned to rough cleaned”
G
seed ratio
33 % Estimated
Seed production can span several years
depending on lead time of project.
See Table 10.14 in Section 10.2.4 or
discuss with seed producer
See Table 10.14 in Section 10.2.4.
If spanning more than one year, average
the expected first and second year yields
Cleaned wild seeds that seed producer
needs to sow
H (100 / G) * F 0.67 lbs Rough weight of seeds to collect
Figure 10-50 | Determining
wild seed needs
The quantity of wild seeds to collect can
be determined from this spreadsheet.
Pearly everlasting (Anaphalis margaritacea)
is used in this example.
Roadside Revegetation: An Integrated Approach to Establishing Native Plants and Pollinator Habitat
283