When to Plant
Most wildflower mixes contain seeds of both annuals and perennials. Most perennial seed species require cold stratification to break dormancy. These have the best success in cold climates if planted in late fall (October to November). They may be planted in spring or summer when supplemental irrigation is available. The annual seed species in the mix has the ability to germinate, as will any of the perennial species in the mix that happen to not require cold stratification (Ex: Coreopsis or Asters).
In mild climates (USDA zones 7 or warmer), seeds are best sown during the cooler months (September to January). Wildflower seeds will have the best germination with ample, consistent supplemental irrigation.
Site Preparation
Proper and thorough site preparation is critical. This provides the best chance for wildflower seeds to compete with existing grass and weed seeds that exist in every site. Some weeds cannot be avoided.
- Clearing the ground is necessary. Seeds must have excellent seed-to-soil contact for germination.
- However, less cultivation is best. Do not cultivate more than 2 inches deep. Otherwise, you bring high numbers of latent weed seeds to the surface that can easily out-compete the wildflower seedlings.
- Use light surface cultivation to remove all existing vegetation. In exceedingly weedy sites, a post-emergent herbicide may be utilized to eliminate the existing weeds. Once weeds have succumbed, remove all dead debris to expose the soil surface with light raking. Repeated herbicide applications may be needed.
NOTE: Wait at least 4 weeks after herbicide applications before sowing any wildflower seeds.
Seed Application
For wildflower seeds, it is helpful to utilize a carrier to mix the seed with prior to sowing.
- Play sand, seed starting mixes, or compost products work well as carriers.
- Blend the proper amount of seed for the size of the planting area with the carrier material, using a ratio of 1 part seed to 2-3 parts carrier. Pre-moistening the carrier is beneficial prior to blending with the seeds.
- Next, separate this blended mix into two parts.
- Then with 1/2 of your mix broadcast by hand or utilize a spreader moving in a North to South direction across the planting area, spreading as evenly as possible.
- Then, use the 2nd half of your mix spreading it in the same way, but in an East to West direction over the site. This allows for the most complete and even coverage of the seed.
- After sowing use a lawn roller to ensure good seed-to-soil contact. Laying and stepping on a 3-4 foot sheet of plywood usually works well for this too, moving systematically from one side to the other.
NOTE: This is a critical step to not run out of seed.
Critical Moisture
Ample moisture is needed for seeds to germinate and develop into healthy seedlings.
- The best results come from thoroughly irrigating the area regularly until the seed has germinated. This can take several weeks. Be prepared to keep the area moist, no matter what. Even a few hours of dry soil can prevent proper seed germination.
- Proper timing of seed sowing during periods of natural rainfall can help, but rain events are never consistent and rarely provide enough moisture for all the seeds in the mix to germinate at their highest potential.
- For the best results, provide consistent and ample irrigation, especially in late spring and summer.
- Once seedlings are up and approx. 2 to 3 inches tall, watering can slowly decrease.
- Wildflowers may be mowed in the fall following the seed set. Mow to a height of 4-6 inches and leave that debris on the ground to promote the natural reseeding of the desirable wildflowers the next season.
NOTE: Some perennials may not germinate until the following spring.
NOTE: Over-watering will benefit competitive weeds at the expense of the wildflowers. Water seedlings enough to promote growth, but not enough to encourage higher weed growth.
NOTE: Control competitive weeds by regular hand pulling and spot spraying as needed. Always remove weed flowers and weed seed heads to limit reseeding.
