Revegetation Guidelines for Western Montana - Global Restoration ...

When designing a seed mix, the number of pounds of PLS of each species is calculated separately
and then divided by the number of species in the mixture. Then take the pounds per acre and
multiply by the total acres to be seeded. For instance, divide the pounds per acre for each species
by four, and then multiply by ten for a mix of four grasses to be seeded on ten acres (for slender
wheatgrass: 12 lbs per acre / 4 species x 10 acres = 30 lbs). Common seeding rates for timothy are
8 – 10 pounds PLS per acre when seeded alone and 4 – 5 pounds PLS per acre when seeded with
another species, usually a legume in pasture situations.
Pure live seed is a measure that describes the percentage of a quantity of seed that will germinate.
Multiplying the purity percentage by the percentage of total viable (germination plus dormant) seed,
then dividing by 100 calculates the PLS content of a seed lot. The PLS measurement standardizes
quality so purchasers can compare the quality and value of different seed lots. Consider the
following example [adapted from Granite Seed Company (2000), used with permission]:
Seed lot A
Seed lot B
Cost / lb (bulk) $1.00 $1.50
Percent purity 75 95
Percent germination 60 80
Percent PLS 45 76
Seed lot A might appear to be a better value because the cost is only $1.00 per bulk pound, whereas
the cost for seed lot B is $1.50. However, the quality of seed lot A is far inferior to seed lot B. To
properly compare the value, purchasers should calculate the cost per PLS pound by dividing the
bulk cost by the percent PLS (PLS cost = bulk cost x 100 / percent PLS). Seed lot B is the better
value at $1.97 per PLS pound whereas seed lot A is $2.22 per PLS pound. Precise ordering of seed
based on PLS allows purchasers to get full value for money spent on seed.
Seed lots may contain dormant, dead, or ungerminable seed or other particles. For example, in a
new seeding of crested wheatgrass with a purity of 98.5% and a germination of 84% (PLS =
82.7%) a seeding rate of 6 pounds per acre (Table 3b value of 6 pounds per acre / 0.827) is
recommended (Cash 2001). For legumes, the percentage of hard seeds is added to the germination
percentage before calculation.
Step 11 – Transplanting
Transplanting salvaged or locally collected plants can complement reseeding and increase overall
revegetation success by providing rapid plant establishment – transplanting circumvents the
susceptible and critical seed germination and establishment stages. Further, sometimes transplanting
is the only feasible method of establishing certain plants. For instance, seeds of many shrubs may
germinate only occasionally, establish very poorly, or reveal slow growth rates in the natural
environment (Munshower 1994).
Although sometimes difficult to attain, successful transplantation of
salvaged or locally collected native plants ensures the preservation of
local native gene pools and ecotypes. To increase success, reduce
weed interference and transplant during periods of early spring or
late fall dormancy. Transplanting during dormant periods can ensure
plants will withstand transplantation rigors and that adequate
moisture will be available during the onset of active growth.
“Island” planting of salvaged
or collected plants can
provide the introduction of
an adapted native seed
source into the site
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