Pollinator Planting to Conserve Native Bees
Procedures for establishing successful pollinator plantings are still a ‘work in progress.’ With ongoing field research underway that will ultimately help us fine tune these recommendations. Based upon several initial field trials at the Penn State University main campus research farms and here at the Fruit Research and Extension Center in Biglerville, we are providing our current recommendations about the best planting method and seed rates for establishing the native flower seed mix developed by USDA-NRCS.
- The seeding rate is fixed at 4 lb/acre or approximately $400/acre depending on the seed source.
- All sites should be sprayed in the next couple of weeks before the first frost to kill actively growing weeds. Use at least 2 qt/A of Roundup to kill remaining summer weeds and actively growing cool season perennials. If poison ivy and/or Virginia creeper are a problem the rate should be doubled.
- Because of the need for a cold period for proper germination of many native wildflower species, we no longer recommend spring planting. Spring planting of native wildflowers resulted in low germination rates and the need to overspray some plots with glyphosate because of summer broadleaf weed problems. Although grasses can be controlled with selective grass herbicides, we have not been able to find a selective herbicide that will control the broadleaf weeds, but leave the native flower species. We, therefore, now recommend only late fall/early winter planting in late October to November. It is important not to plant earlier than late October because warm fall days may allow some germination of native wildflower seed, with the young plants being killed with the first heavy freeze.
- Drill Seeding - Because of the different sizes, weights, and characteristics (tufted, untufted, winged, bare, big, little, smooth, fuzzy, etc.) of the seeds we're using, we have had problems with most typical seeders or drills that do not have a seed box attachment specifically for small seeds and an agitator bar that keeps the seeds flowing into the drop tubes and keeps the seed mixed in the seed bins. Working up the sites with a disc for planting with a Brillion drop seeder after a Roundup spray, just brought new weed seed to the surface where it could germinate and crowd out the native flowers. Penn State and USDA-NRCS have obtained a 6 food wide Truax no-till drill that is generously being loaned to the Penn State University FREC from the PA Game Commission. This drill will be available to growers enrolled in the program from October until next April. It has a modified seed box attachment with an agitator bar that is necessary to get the seed flowing evenly out of the box and which will knife the seed into the soil and make tillage with a disc unnecessary. The drill can be road-hauled for 10-15 miles, but will need to be trailed for distances longer than that. We don’t know the weight of the drill yet, but have been told a typical snowmobile or ATV trailer should work for longer hauls. Contact Dr. David Biddinger at the PSU Fruit Research Lab in Biglerville at 717-677-6116 ext. 8 or the farm manager, Terry Salada at the same number, ext. 212, to reserve the drill. We will have instructions for use and settings for planting at the 4 lb/A rate available.
- Broadcast Seeding – because of the different weights, sizes, and shapes of the various flower seeds, broadcast trials indicated the need for an inert carrier material such as clay kitty litter to both bulk up the mix for broadcasting and to better distribute the different sized seeds. Using 40 lb of kitty litter/A with the seed mix, we had some success, but distribution was not as even as with a drill or drop seeder. Through mixing of the clay and seed mix is essential. Currently, we are recommending broadcast applications only where the slope of the site is too steep to use a heavy drill. Areas planted by broadcast seeding should be closely mowed (2 inches or less) so that bare ground is visible between remaining plant stubble, and all loose plant debris should be raked and removed from the site. General turf grass, or pasture broadcast seeders, as well as truck-mounted road salt spreaders, and ATV-mounted deer food plot seed broadcasters, are all acceptable for broadcasting the seed/kitty litter mixture. After broadcast seeding, the area should be lightly compacted with a field cultipacker, a lawn roller, or by driving over slowly with a truck or ATV.
- Post-planting – Growers should not expect the plantings to come up the first year as a solid bed of flowers with a heavy bloom. Be patient and expect the plantings to look somewhat weedy for the first season until all flowers get established. In spring and summer of next year, anticipate the emergence of annual weeds in the newly seeded areas growing alongside your perennial wildflower seedlings. Without management, the annual weeds will out-grow and out-compete the slower growing perennial wildflowers in the first year, and set seed creating additional future weed problems. The preferred way to control weeds after planting is to mow the newly seeded area at 3-6 inches or whenever the majority of the annual weeds are in full flower. This mowing will prevent the annual weeds from setting seed, and deplete their energy reserves. Based upon your individual weed species, mowing may be required 3 or 4 times during next year’s growing season. Don’t worry about harming your wildflower seedlings, most of them grow slower than the annual weeds and will sit below the blades of the mower. Those that grow more rapidly can withstand some clipping, and are less harmed by mowing than they are by competition from weeds. Similarly, most newly planted wildflowers will not flower in the first year anyway. During this time they are establishing their root systems, and are not greatly impacted by the occasional mowing. Mowing will not harm these plants as they set roots. The annuals in the mix (clovers and partridge pea) should germinate in the spring and provide flowers the first year. Most of these species in the mix will bounce back from mowing and continue to flower. Should biannual or perennial weeds persist (such as Canada thistle) they should be spot sprayed as soon as possible to avoid contaminating site before wildflowers get well established.
