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How Seeding Rates Can Affect Species Composition in Pollinator Plantings

Now that fall is coming to an end and winter begins to show its face, it is time to start thinking about establishing pollinator plantings.  One thing to consider is what species to plant, and which species are best adapted and most compatible in a multiple specie mixture.  In 2016, the staff at the Elsberry, Missouri Plant Materials Center (PMC) planted a demonstration pollinator planting to investigate establishment of multiple plant species beneficial to the Monarch butterfly and other valuable pollinators.


Species were selected from the conservation practice standard for rare and declining habitats (NRCS conservation practice 643), and a list of milkweed species recommended for the Midwest.  Ten species were selected for their value to Monarch butterflies, commercial availability of seed, seed expense, and bloom time with relation to the presence of Monarch butterflies in the Midwest (May through September).  Listed below are the native forb species used in the demonstration planting along with their composition in the mix. 

 

Forbs and species composition of the seed mix.

Scientific Name Common Name Composition of Seed Mixture (%)
Asclepias incarnata Swamp Milkweed 1
Asclepias syriaca Common Milkweed 2
Asclepias tuberosa Butterfly Milkweed 1
Aster novaeā€angliae New England Aster 15
Echinacea purpurea Purple Coneflower 12
Eryngium yuccifolium Rattlesnake Master 12
Heliopsis helianthoides Oxeye False Sunflower 12
Monarda fistulosa Wild Bergamot   15
Rudbeckia hirta Blackeyed Susan 15
Solidago rigida Stiff Goldenrod 15

 

The planting was seeded at the PMC in February 2016 as a winter dormant planting at a rate of 20 and 40 seeds/ft2.   First year management consisted of mowing the planting 3-4 times to control weeds that would potentially outcompete the native forb seedlings.  In 2017, the planting began to mature, and several species began to show their beautiful flowers.

Evaluations indicate that while the higher seeding rate did increase the abundance of species, it was not significantly higher for most.

 

Native Plant Species Abundance
(Averaged along a 100 foot transect)
Image of chart depicting native plant species abundance (averaged along a 100 foot transect.

Lowering or adjusting the seeding rates of wildflower species for pollinator habitat plantings may be effective in keeping costs for these plantings more reasonable.  However, lower seeding rates may also lead to increased open spaces in the planting.  This may cause other issues such as erosion or weediness depending on the site.  The addition of less competitive grasses may help in addressing erosion or weediness issues.  At the time this demonstration was developed, NRCS required a minimum of 9 species for most wildlife-friendly plantings, which is the requirement this study was developed around.  Currently, the NRCS minimum requirement is a 20 species forb mixture for pollinator, monarch butterfly, and natural community plantings.

When developing a pollinator mix be sure to consider all the resource issues at the planting site and pay careful attention to the composition of the mix to promote more desirable species, such as milkweeds for Monarch butterflies.  Crucial to your success is to control weed species before planting, practice good management of the stand in the first couple of years, and above all be patient with your pollinator habitat planting! 

 

The demonstration plot in this photo shows species like pale purple coneflower, greyhead coneflower and horsemint.
A seed mixture at 20 seeds per square foot still demonstrates plenty of color for pollinators to be attracted to.
 
The picture shows a comparison of two different seed mixtures in bloom.
A bottomland field demonstrating several different species blooming and providing food for pollinators.
 
A painted lady butterfly feeds on the flower of a New England Aster plant
A painted lady butterfly feeds on the flower of a New England Aster plant.

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