Cleaning Seeds

You’ve been working hard to collect those seeds and you’ve made sure to dry them thoroughly so they don’t mold. Now it’s time to clean them. Basically, this is separating the seed from the pods or stalks. This sets you up for successfully getting seed-to-soil contact when you sow them.

A few words of safety. Seeds are dusty so take safety measures to protect your eyes and lungs. For the manual cleaning, I wear a face mask and eye protection. When hammermilling, we add ear protection.

I emphasize the importance of knowing what the seed looks like for each plant you are processing.  This will help you determine the proper screen size to use and will ensure you’re not tossing out the seed thinking it is the residual dust. Seeds from Eastern shooting star (Dodecatheon meadii) and tall cinquefoil (Potentilla arguta) are tiny and it would be easy to toss them thinking they were dust particles.

The Tools We Use
  • Hammermill
  • 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
  • Safety items: Face mask, eye protection, gloves

Cleaning Fluff and Large Seeds

The seeds with fluff 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 to fit a plastic bin.  I have no worries about losing seed because the screen isn’t securely set.  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 has no ragged edges to catch your gloves and clothes. 

Step 1: I start with fluff seed on my hardware cloth screens.

Step 2: Then I rub or scrape them across the hardware cloth and the seeds fall into the plastic bin below.

Step 3: When finished, the seeds are gone and the stems remain. The stem is tossed into the chaff bag.

Step 2: Then I rub or scrape them across the hardware cloth and the seeds fall into the plastic bin below.
Step 3: When finished, the seeds are gone and the stems remain. The stem is tossed into the chaff bag.

Silphium seeds are large. I process them the same as I process fluff seeds. The photos show me using my 12×12 screens but I also use the hardware cloth screens as well.

Step 1: Silphium spp seeds are attached quite securely around the edge of the seed head.

Step 2: Rubbing them across the screens releases the seeds into the plastic bin

Step 3: In the end, I’m left with the bracts and stem, which I toss into my chaff sack.

Step 1: Silphium spp seeds are attached quite securely around the edge of the seed head.
Step 2: Rubbing them across the screens releases the seeds into the plastic bin
Step 3: In the end, I'm left with the bracts and stem, which I toss into my chaff sack.

Cleaning Milkweed Seeds

Milkweeds have their own cleaning technique. Timing is critical. Waiting until the pods pop open makes it difficult to separate the seeds from the fluff as it is wildly flying around! To check for maturity before collecting, I push the seam. If it pops open and the seeds are brown; they are ready. The gallery of pictures show the method for cleaning milkweed.

Step 1: Pop the pod open at the seam.

A milkweed with mature seeds

Step 2: Pull the pod back exposing the seeds and the white fluff.

Step 3: Rub your thumb over the seeds from bottom to top. The seeds without the fluff will fall into the bucket.

Step 4: Continue rubbing around the fluff core until all the seeds are removed.

Step 5: This is what the milkweed fluff will look like when the seeds are completely removed.

Step 2: Pull the pod back exposing the seeds and the white fluff.
Step 3: Rub your thumb over the seeds from bottom to top. The seeds without the fluff will fall into the bucket.
Step 4: Continue rubbing around the fluff core until all the seeds are removed.
Step 5: This is what the milkweed fluff will look like when the seeds are completely removed.

Processing Hammermilled Seeds

Hammermilled seed need further screening to remove the chaff. The hammermill simply breaks the pods apart; it doesn’t separate the seeds. I use 4 sizes of screens with round holes: 3/16, ¼, 3/8, and 5/8. I purchased these from Hoffman Mfg. My frame is 12” x 12”, which is a good size for the amount of seed that we process. 

Step 1: This shows what hammermilled seed looks like. The whole seed pods are on the left.

Step 1: This shows what hammermilled seed looks like. The whole seed pods are on the left.

Step 2: We chose a screen hole size that accommodates the seed size. Scoop the hammermilled seed onto the screen.

Step 3: Jiggle and shake the screen so that the seeds (heavier items) fall through and the chaff (lightweight material) stays on the screen.

Step 4: Dump the chaff into another plastic bin, then into the chaff bag. This picture shows the whole work flow system.

Step 2: We chose a screen hole size that accommodates the seed size. Scoop the hammermilled seed onto the screen.
Using a screen to separate the seed from the chaff.
Step 4: Dump the chaff into another plastic bin, then into the chaff bag. This picture shows the whole work flow system.

The Chaff

The chaff, all the stuff leftover from the actual seeds, has small amounts of good seed in it. The chaff goes into bags labeled for their appropriate habitat, e.g. dry chaff, wet chaff, savanna chaff. This makes it easy to spread the chaff into the appropriate habitat.