Wildflowers
Kentucky’s prairies were once known for their
breathtaking floral displays. Prairie wildflowers coexisting with prairie
grasses formed one of the most complex and intricate plant communities in the
world. The native prairie is now one of the rarest plant communities in North
America, having been largely destroyed by modern land use practices. Wildflower
prairies enhance biodiversity in any given area, providing unique wildlife
habitat while at the same time returning the land to its natural beauty.
Site Selection
Prairies and meadows require sunny, open sites.
An area should receive at least 6 hours or more of full sunlight and have good
air circulation. South, west, and east-facing slopes receive more sun, and are
hotter and drier; therefore they are usually well suited for prairie meadows.
North-facing slopes are protected from the sun, and stay cooler and more moist;
therefore these slopes are best suited for shade tolerant species. You must
match wildflower species requirements with soil moisture and duration of
sunlight. Some species thrive in full sun with dry soils while others do better
in partly shaded, wet conditions (see Wildflower Selection Guide).
Soil types are directly related to soil moisture
and can be broken down into three basic classifications: sands, loams, and
clays. Sandy soils are loose and easy to work. They allow water to drain easily
and tend to be low in nutrients. Clay soils tend to be dense and hard to work.
They have a high water-holding capacity and are generally rich in nutrients.
Loamy soils can be considered intermediate between the previous two types. Loamy
soils combine fertility and moisture-holding capacity with good drainage. Loamy
soils can be considered the best of the three types.
Site Preparation
Site preparation is the most important factor in
establishing a wildflower prairie. Use caution when establishing a prairie on
sites with extended histories of weedy competition, especially if the
competition includes fescue and/or sericea lespedeza. Such sites will require
extensive preparation to reduce the competition for nutrients, water, and
sunlight. Reducing the existing vegetation is the first step in site
preparation. Smothering, cultivating, chemically treating, or some combination
thereof can accomplish this task.
If you are establishing a small prairie, you may
choose to smother the competition. This technique is simple, effective, and
requires no chemicals or special equipment. Cover the area desired for the
planting with black plastic, plywood, carpet or thick layers of leaves for a
full growing season. This will restrict the sunlight and kill all existing
vegetation.
Cultivation (plowing, tilling, or disking)
requires intensive labor but gives desired results. Cultivation should start in
the spring and continue through fall if herbicides are not used. Cultivate every
2 weeks or less at a depth of 4-5 inches to keep the vegetation from resprouting.
This method takes one full growing season. If herbicides are going to be used,
chemically treat the area, allow 2 weeks for uptake of the chemical, and
cultivate 3 to 4 times to form a good seed bed.
Chemical treatment* of areas that you want
to plant in the same year is the best option. Chemical treatment can give fast
and cost-effective results if done correctly. Some wildflower species are
resistant to a herbicide known as Plateauâ.
This herbicide used in combination with Roundupâ
or a similar chemical can give fast results and provide residual effects for up
to 8 weeks. If you wish to establish wildflower species not resistant to Plateauâ,
other herbicides, such as Roundupâ,
will suffice for the initial spraying, but do not give the residual effects. Do
not plant areas treated with Roundupâ
or related herbicides for at least 2 weeks. Best results can be obtained by
using prescribed burning* on the area after the chemical treatment has killed
the existing vegetation. This helps reduce excess duff material that can
accumulate over the years, assuring good seed-to-soil contact. Do not plant
wildflowers in areas treated with Atrazine within the last 2 years. Some prairie
grasses can tolerate low levels of Atrazine, but prairie wildflowers cannot.
Atrazine will break down in 2 to 3 years depending on soil type, precipitation,
and the amount originally applied.
Lime & Fertilizer
On first year plantings, the addition of
lime and fertilizer* is not recommended as long as the soil pH is above 5. In
the first year of growth, both wildflowers and native warm season grasses put a
lot of energy into root development. By applying lime and fertilizer the first
year, you will be promoting weed growth. However, you can lime and fertilize
stands that are well established and see productive results. Some federal
programs require lime and fertilizer on enrolled plantings. You can mix the seed
with the lime to facilitate broadcast seeding. However, apply the fertilizer as
late as possible to minimize cool season weed growth.
Planting Techniques
There are 4 basic methods of establishment
for wildflowers. The seed can be no-till drilled into a chemically treated sod,
drilled into a prepared seedbed, broadcast seeded onto a prepared seedbed, or
they can be established with the use of transplants. The best time to plant
wildflowers is during the spring and early summer months. Shoot for a target
date ranging April through May depending on soil temperature and moisture. Many
prairie wildflowers are warm season plants that germinate best after the soil
temperatures have warmed up. In any wildflower planting you should incorporate
some native warm season grasses into the mix for extended weed suppression.
Wildflowers and native grasses grow together naturally with minimal competition.
Some native warm season grasses* that should be considered in the wildflower
planting include sideoats grama, little bluestem, big bluestem, and indiangrass.
Do not include switchgrass or gamagrass. They can dominate an area, shading out
the wildflowers.
Drilling the seed, whether into a chemically
treated sod or a firm seedbed, has its benefits. With the use of a good drill,
seed calibration and depth can be adjusted accurately. A no-till drill can be
used on highly erodible sites to minimize soil erosion. Remember good
seed-to-soil contact is essential. Do not drill the seed too deep. A planting
depth of 1/4 inch is desired. Drilling the seed will allow you to cultivate the
planting during early establishment for extra weed control. Be careful to stay
between the rows when cultivating.
Areas encompassing one acre or less can be
broadcast seeded by hand. On larger plantings, a mechanical broadcast seeder can
be used. The seedbed must be well prepared and firmed with a cultipacker. The
ideal seedbed should be smooth and firm, barely showing footprints after walking
over it. The prairie seed can be mixed in a larger volume of a lightweight,
inert material such as sawdust or peat moss. Slightly dampen the material so the
seed will stick to it. Mix thoroughly to distribute the seed equally within the
mix. Take approximately one half of the mix and spread it across the seedbed
evenly. If you run out, use enough of the remaining mix to finish. After the
entire area has been seeded once, go over the area with the remaining mix
perpendicular to your first seeding. Roll the site with a roller or cultipacker
to ensure good seed-to-soil contact. Do not roll the site if the soil is wet.
Wait until the soil dries to avoid soil compaction. You can cover the area with
a light mulching of clean, weed-free straw. This will help hold in moisture,
increase germination, and combat soil erosion. Do not mulch the area too
heavily; some soil should be visible through the mulch. Never use field hay
because it will contain unwanted weed seeds.
Transplants are often preferable to seeds on
small prairie gardens. Perennial wildflowers are sometimes slow to grow from
seed and can take up to 3 years to bloom. Transplants often bloom the first year
and should be spaced approximately 1 foot apart.
Spring and summer plantings can benefit from
watering during drought conditions. Watering helps encourage germination and
seedling survival during the first few weeks. Water early in the morning.
Watering midday or afternoon can be less effective and is not recommended. Be
careful not to water too much.
Planting Rates
Wildflower seed can be very expensive and
ultimately it comes down to what you want to spend on a planting. Best results
can be obtained by seeding 8-10 Pure Live Seed (PLS) pounds of wildflowers
("forbs") in combination with 1-2 PLS pounds of native warm season
grasses per acre. Keep in mind at that rate it can be very expensive depending
on which wildflower species you choose to plant. Successful plots can be
obtained by seeding 3-5 PLS pounds of wildflowers in combination with 2-3 PLS
pounds of native warm season grasses. Each time you reduce the poundage of
wildflowers in a plot, increase the poundage of native warm season grass. This
will help keep out unwanted, invasive grass species. In plots where wildflowers
are the main focus, plant shorter varieties of native warm season grasses such
as little bluestem or sideoats grama. Taller grass species such as indian grass
and big bluestem may be planted if the main focus is diversity and not
wildflowers. All four grass species are resistant to Plateauâ.
Weed Control and Maintenance
Perennial wildflowers and native
warm season grasses sometimes take a year or two to become fully established and
weedy competition can further slow the establishment time. The herbicide Plateauâ
can greatly enhance the establishment process by providing excellent weed
control. (See Wildflower Selection Guide for Plateauâ-resistant
species.) Herbicide treatment can replace mowing for desired weed control if the
selected wildflower species are herbicide tolerant.
If chemical treatment is not an option,
periodic mowing will help sunlight continue to reach the ground during the first
year. Mow at a height of 6 to 8 inches to avoid cutting the desired species.
Mowing once a month can be effective during the first year depending on
rainfall, weed density, and height. Toward the end of the growing season,
(August - September) do not mow the planting. Allow the area to establish as
much growth as possible to protect the young plants during the winter. The
following spring, mow the entire area close to the ground and rake it if
possible. This will allow sunlight to penetrate the ground, facilitating
germination and plant growth. The herbicide Plateauâ
may again be used if resistant species were planted. Periodic mowing may be
required depending on weedy competition.
Long-term management includes prescribed burning*
(if possible) or mowing*. Timing of the burn for wildflowers is somewhat
different than for native warm season grasses. It is recommended that you burn a
wildflower prairie in the fall after a killing frost sets the plants into
dormancy. The fall timing for a burn may negatively affect native warm season
grasses if they are present in the planting. (Contact your local wildlife
biologist for site specific recommendations.) Spring burns on the other hand
often harm young rosettes that are produced by the wildflowers very early in the
spring. Fall burns reduce the seed source and cover abundance for wildlife. For
this reason, it is recommended that you break up any planting greater than one
acre into 3 to 4 units.
