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11Determine seed and plant quantities
Choosing the quantity and stock type is just as important as selecting
plant species. This decision will greatly affect project establishment. It
is influenced by overall project goals, budget, and time frame.
When using native seed, we recommend calculating the amount
of seed needed for a particular species by estimating the amount
of native seed of that species to apply per square foot or per acre.
Native seeds vary greatly in size and shape, depending upon the
species you are using. A species with a high seed count per ounce
will require much less seed to cover a given area than another
species with a lower seed count.
For example, 1 ounce of Broad-Leaved Purple Coneflower
contains 6,600 seeds. In contrast,
1 ounce of Foxglove Beard Tongue
contains 115,000 seeds. To provide the same coverage per acre,
you need approximately 17 times as much
Determining how many total seeds per square foot are enough for
a site depends upon project goals, budget, and resources. Cardno
native seed mixes are designed with an application rate of 50 to
95 native seeds per square foot, depending on the mix. Acceptable
results can be achieved by using an approximate seeding rate of 20
to 30 seeds per square foot, including grasses and forbs.
Note that some species are early successional, or “pioneers,”
meaning they are dominant early on in project establishment. Others
are more conservative and do not establish readily from seed. These
more conservative species might be more suitable to be included as
plugs or larger container sizes. Cardno’s nursery team can discuss
these options with you.
The size of the live plant to use will depend on budget and project
expectations. Plugs are less expensive than quart or gallon-sized
stock, but they will be less showy after planting. After a full year
in the ground, it is difficult to distinguish a planting installed with
plugs versus gallons. However, because gallon stock is larger at
installation, they are typically second-year plants, meaning they will
be more likely to bloom during the year following installation.
When estimating the number of plants, keep in mind plant size at
maturity. Many native species are at least 3 feet tall and 1 or more
feet wide at maturity. While a planting density of 1 foot on center
will look great during the first year, the plants will be very crowded
once they mature. Spacing larger plants 18 or 24 inches on center
will be less costly and just as showy in the end.Prepare site for installation
Prior to installing native seed or plants, the site needs to be
prepared properly, which involves identifying existing native plants,
removing unwanted vegetation, stabilizing erodible areas, and
preparing the plant and seed beds. Before making modifications to a
site, however, be sure to obtain any required permits and put proper
erosion control measures in place. Cardno can assist with your
permitting and erosion control needs.
Creating a Native Landscape