Once the seeds are dry, they need to be cleaned. Seeds are dusty so safety measures need to be taken for your eyes and lungs. For the manual cleaning, I wear a face mask and eye protection. When hammermilling, we add ear protection as well.
The tools we use include:
- Two sizes of hardware cloth “screens” for “fluff” seeds
- Small screens for screening after hammermilling
- Various size scoops
- Various size paper, plastic, and feed bags
- Face mask
- Eye protection
I would emphasize the importance of knowing what the seed looks like for each plant you are processing. This will help you know which size screen to use and will help you to be certain you’re not tossing the seed away thinking it is the residual dust. Seeds of plants like Eastern Shooting Star (Dodecatheon meadii) and Tall Cinquefoil (Potentilla arguta) are small enough that it would be easy to toss them out thinking they were dust particles.
The seeds with fluff on them are scraped or rubbed across the screens with the bin underneath. Some examples of fluff seed include asters and goldenrods. Jim custom made the screens I’m using to fit a specific plastic bin so when I was scraping, the screen part and the bin part would not separate. The bins are made of ¾” pine cut to 21 ½”long, 15 ¼” wide, and 5 ½” deep. Construction is with screws. One is covered with ¼” hardware cloth and the other is covered with ½” hardware cloth stapled to the wood. Make sure the hardware cloth is cut so there are no loose metal ends as these will catch on your gloves and clothes.
Silphium spp seeds are very large and I process them in the same way I process fluff. The photos show me using my 12×12 screens but I also use the hardware cloth screens as well.
Milkweed seed is cleaned a bit differently. Timing is so critical with these seeds. If you wait until the pods pop open on their own, the dry fluff makes it difficult to separate the seeds from the fluff as it is wildly flying around! One method that I use it to roll the pod in my hand; if the seam pops open, then the seeds are usually brown and ready. This is not foolproof as I’ve had the seam split and there be green seeds inside. They will turn brown eventually, but I can’t attest to their viability. The gallery of pictures are helpful for understanding the method for cleaning milkweed.
Hammermilled seed will need further screening to remove the chaff. I use 4 sizes of screens with round holes: 3/16, ¼, 3/8, and 5/8. I purchased these from Hoffman Mfg. (http://www.hoffmanmfg.com/products/hand-screens.html). My frame is 12” x 12”, which is a good size for the amount of seed that we process.
The chaff, all the stuff leftover from the actual seeds, has small amounts of good seed in it. I tend to collect the chaff in bags that I have labeled as 1) dry chaff, 2) wet chaff, 3) savanna chaff. This separation allows me to spread the chaff into the restoration areas best suited for that seed to germinate. Often I’ll use the chaff for overseeding certain areas.