Plant Material - Project Planning and Management for Ecological Restoration - page 115

Purchasing Seed
Seed is regulated by the government, and a number of requirements are placed on seed providers,
such as testing the seed lot for purity and germination. These two measures are important for un-
derstanding exactly what you will be purchasing.
Purity
The ability of seed to be separated or collected with a minimum of nonseed material is highly
variable. All native seed stock is sold by the bulk pound and typically includes live seed, dead seed,
vegetative parts, dirt, sand, and seeds of other species. Most seed suppliers and growers perform
standard cleaning operations to remove the nonseed material. However, there is a point where the
level of effort exceeds the resulting product
Providers sell nongarden seed by the bulk pound. The cost for a bulk pound includes all those
“nonseed” elements listed earlier. Therefore, knowing the purity of the seed will enable you to
determine the seed quantity and the cost of that seed being purchased.
Calculating the quantity of seed from the bulk seed poundage is a simple step and is explained
in box 8-1.
Germination Rate and Viability
Germination rate and viability are different terms addressing aspects of growth potential in seed
stock. Viability describes whether a seed is capable of germinating by establishing the presence
of an embryo plant within the seed coat. Germination rate addresses the total number of seeds
that actually begin to grow a seedling in a sample. Viability includes germinating seed plus the
dormant seed that requires longer to actually germinate.
Knowing the viability of the seed stock is critical for planning a successful project, especially
when using rare or endangered species. Several environmental factors contribute to the develop-
ment of a seed, and many native species produce seeds that appear to be normal externally and
internally but that fail to germinate for various reasons, including atypical rainfall at a critical time
of seed development, genetics, fungus infection, or insect herbivory, to name just a few. Seed
viability can vary from season to season, making it difficult to get the same results. A simple ger-
mination test that you can perform involves placing seeds on moist germination paper or a moist
paper towel and maintaining them under controlled conditions to promote germination. After
about seven to fourteen days, you can calculate the percentage of seeds that have germinated. A
more frequent, and quick, test for germination is to apply tetrazolium chloride, although this test
is less accurate than a full test for viability.
In some cases, you may want to limit using seeds for testing but may still need to verify seed
viability. Radiographs (x-rays) have been used in cases where there are too few seeds to permit
using some on testing for viability. The radiograph will detect the presence of the primitive root
but cannot predict if it is capable of germination. Radiograph tests can also determine whether