Cleaning seed

Hi, David!  Welcome to the site! 
That's a very timely topic to bring up now! I've been working on collecting seed for the exchanges I participate in, as well. 

Does your query relate to a particular situation (e.g. tiny seeds?)?  It might be helpful to elaborate, or to list the species you are working with, to understand the type of tips being sought... ? 

It's mostly Penstemon seed. 

I get a lot of seed from a single plant but it comes with a lot of "waste" that needs to be seperated.  It's taking me a long time to get anywhere and I wondered if anyone had any time saving hints.

Yes, penstemons can certainly produce a copious amount of seed!

Without resorting to graduated sieves and such, as the pros would use, I usually do some or all of the following:
For separating chaff from seed, it seems to come down to the size of the seed and the chaff, and also the specific density of the seed compared to that of the chaff. 
If the bits of chaff aren't too tiny, I usually just pick them out with tweezers, swirling the seeds around in the bowl to get it all.  E.g. If I end up crushing some penstemon seedpods to get more seeds out, I'd pick the bits out this way, usually.
If the chaff is smaller, I have also, at times, dumped the mix out onto a textured paper towel, then tipped and jostled the paper towel to move the mix along the slope - if the chaff is lighter or differently-shaped compared to the seeds, it will often separate out from the seeds.
If the chaff is dust-like or has very low density compared to the seeds, then it may be possible to carefully blow the chaff out of the bowl.  Also, swirling the seed around a flat-bottomed bowl can separate the chaff well enough that it can be wiped out of the bowl with a finger or damp tissue. 
All of these work reasonably well with smallish quantities of seed - I'd clean a bigger batch of seed in parts.

What do other people do?

As much as possible, I try passive seed cleaning... placing the ripe (just starting to split open) pods and stems into a paper bag, the stems upside down, then let them sit in the dry bag in my basement, much of the seed will drop out, possibly enough so that you don't need to fuss with getting the rest of the seed out.  I'm not a fan of cleaning certain seed, penstemon being one of them, as the pods stink, and they are often very hard, pointy and sharp, making cleaning a bit of a challenge.  For certain seed heads once dried sufficiently, such as with many alliums, I can close the bag and bang it a few times against a table, releasing lots of seed, or even squeeze the bag lightly to help release seed rather than crushing the pods and making lots of difficult to clean chaff.

For some items, I want all the seed and must manually clean them.  I don't use sieves or anything fancy.  I just use a shoebox top... it's basically low and flat but the turned up edges keep the seed in.  Then, killing two birds with one stone, when I watch TV, I can sit there and crush pods and hand separate seed.  It's amazing how much seed I can get cleaned while watching a movie, being productive at the same time as enjoying some entertainment.  Sometimes, even my two daughters will ask to help clean seed :o

Oh, yeah, good reminder about paper bags!  Works great, too, for geraniums, and plants that tend to shoot their seeds around.  (I have a couple of bags of seed pods sitting over there right now.)

My current dilemma is how to deal with Hedysarum seeds... short of handling each and every one to remove the seed from the pod (which I'm currently doing).  Each seed is enclosed in its own close-fitting little shell; as the seeds are flat, it is hard to crush the seed pods without possibly damaging the seeds.  Bending the seed pod pops it open, but it's fussy to do on seed pods that are about 1/4" diameter.  If not for the Dept. of Agriculture requirement to remove all chaff and non-seed material in order to send seeds across the US border for the NARGS seedex, I wouldn't bother trying to remove the seed pod at all...  Any ideas?

Welcome to the forum, David!

That a really good idea with the paper towel, Lori.I had never thought of that before.  I would imagine you would also get varying success depending on the kind of paper towel employed (rougher, smoother, softer, harder).

I will never forget the first time I gathered witchhazel (Hamemelis virginiana) seed pods.  I had them in a paper bag, just because of convenience.  I was very fortunate to be sitting quietly, reading a book, when they had dried enough to dehisce.  It started to sound like a batch of popcorn was beginning to pop.  I didn't realize what it was until I saw a seed sail across the room and traced its trajectory back to its origin!  (Note to anyone: a lunch bag is not heavy enough to contain the forceful ejection of witchhazel seed.)

I don't think I have too much to add to the tips, except perhaps if you are dealing with very light matter.  Static electricity might be your friend, allowing much of the light chaff to be removed.  Or it could be a nuisance,  with everything stick your your hands, etc., or being repelled.  I deal a lot with papery Lilium seed, and static electricity on my light table is problematic.  I keep a spray bottle filled with water handy to dissipate the charge.  But then, remember that seed must be fully dry before storing!

BTW, for anyone who makes styrofoam troughs, a water spray bottle is definitely your friend.

Lilium michiganense seed photographed on a light table.

Skulski wrote:

Oh, yeah, good reminder about paper bags!  Works great, too, for geraniums, and plants that tend to shoot their seeds around.  (I have a couple of bags of seed pods sitting over there right now.)

My current dilemma is how to deal with Hedysarum seeds... short of handling each and every one to remove the seed from the pod (which I'm currently doing).  Each seed is enclosed in its own close-fitting little shell; as the seeds are flat, it is hard to crush the seed pods without possibly damaging the seeds.  Bending the seed pod pops it open, but it's fussy to do on seed pods that are about 1/4" diameter.  If not for the Dept. of Agriculture requirement to remove all chaff and non-seed material in order to send seeds across the US border for the NARGS seedex, I wouldn't bother trying to remove the seed pod at all...  Any ideas?

/ Lori, I have one trick I use with many pea seeds and I learned it years ago from Panayoti.  The pods are placed in a paper bag which is given a gentle shaking every few days.  The pods will eventually open and spill the seeds to the bottom of the bag.  It's quite easy to remove the pods because they were never broken.  If you have a couple of pods that still have not disgorged their contents, they are usually partly open and it's easy to force them open completely with the tip of scissors or with needle-nose pliers.  Some pea seeds (such as Astragalus utahensis), have very hard furry pods with very sharp tips.  I worked on those once with fingers which were not as tough as the pods and then I ran into Panayoti who gave me the tip.  Thanks again, Panayoti

An excellent tip for pea seeds!  It's working great for Lupinus sericeus (can hear them popping in the paper bag!) but it seems the hedysarum is another beast again.  The loments break up into individually-sealed flat, round capsules and fall to the ground... makes perfect sense that they must very likely split open at some time, but despite being completely dry, they weren't doing it either in the house or around the plant outside!  ??? 
So, I did end up handling each seed to remove the pod after all.  Oh well, it was a good exercise in patience.  :D

Skulski wrote:

An excellent tip for pea seeds!  It's working great for Lupinus sericeus (can hear them popping in the paper bag!) but it seems the hedysarum is another beast again.  The loments break up into individually-sealed flat, round capsules and fall to the ground... makes perfect sense that they must very likely split open at some time, but despite being completely dry, they weren't doing it either in the house or around the plant outside!  ???   
So, I did end up handling each seed to remove the pod after all.  Oh well, it was a good exercise in patience.   :D

Lori, it must break up in nature so why not try scratching a few right into the top inch of your mix without removing the seeds?  I think I did that years ago with Eriogonum shockleyi (another Panayoti tip) and it worked fine.

Yes, I wouldn't  mind having a couple more Hedysarum boreale to fill space in that poor, dry area out there - they are very showy in bloom -  so I'll do that.  (I suspect most of the seeds that fall on the ground blow away, normally.  I always wonder if someone downwind of my yard gets all my plants... haven't seen any evidence of it yet, though.)  The reason I was removing the seed pods, though, was to package "clean seed" for seedexes, hence the effort.  :)

Skulski wrote:

My current dilemma is how to deal with Hedysarum seeds... short of handling each and every one to remove the seed from the pod (which I'm currently doing).  Each seed is enclosed in its own close-fitting little shell; as the seeds are flat, it is hard to crush the seed pods without possibly damaging the seeds.  Bending the seed pod pops it open, but it's fussy to do on seed pods that are about 1/4" diameter.  If not for the Dept. of Agriculture requirement to remove all chaff and non-seed material in order to send seeds across the US border for the NARGS seedex, I wouldn't bother trying to remove the seed pod at all...  Any ideas?

If the pod break up into individual seed-containing pieces, each piece is in essence a nut and you don't shell a nut, do you? (I mean before sowing it - not eating it.)

When I clean seeds I use the same methods as suggested here - depending on type and volume and time, the paperbag method is my favorite even for very small seeds and fern spores.

I have used all of the methods mentioned usually in combination. For difficult seed such as Penstmon or Eriogonum I find the use of sieves, speeds the process along.
I use a variety of sieve sizes to sift or scalp off the course chaff (stems, dry leaves etc.) going down a size or two each time until the seed and remaining chaff are about the same size. I then rub the remaining chaff and seed between my hands to pulverise the chaff further.  Another sieving through a very fine sieve to remove the dust. Next I winnow the seed and remaining chaff in a light breeze or in front of a small fan.(keeping in mind that there comes a point of diminishing return) The last step is too pour the seed on to a tray and separate the seed from the waste with a small brush. I flick the seed to one corner and the waste to another.

For cactus fruit I squeeze the pulp and seed into a sizable container of lukewarm warm water and whisk the solution with a wire whisk to thin it out. Then I strain it through a kitchen stainer. The seed and remaining pulp is emptied onto a tray and spread out to dry. The dry residue can then be rubbed to release the seed. Last a final sifting with a fine sieve to get rid of the dust and any remaining dried residue.

For me, Penstemon seed is the easiest species to clean.  I usually collect whole stems or, at least whole capsules, in white paper sandwich bags (so I can make sure all the seeds have been emptied from the bags when I process them).  I start with several cheap, thin, white paper plates with fluted edges and a common, large-mesh household strainer, pouring everything (seeds, capsules & stems) into the strainer without crushing anything.  Most of the seed will fall through that size mesh.  I set the seed aside on one of the paper plates.  If I need every possible seed, I then crush the capsules while they are still in the strainer with a double-rubber-gloved hand (yes, capsule pieces are sharp!).  Chaff and seed fall through the strainer onto a separate white paper plate and are set aside.  In a small-mesh strainer, such as a tea strainer, I pour in a small quantity of the nearly-pure seed and rub it vigorously against the mesh with my gloved hand, rubbing off the outer coating.  I repeat until the entire lot of this nearly-clean seed is rubbed.  If the seed is very small, it may fall through the mesh along with the powdery chaff and outer coating.  I catch it on a clean white paper plate.  With the outer coating rubbed off, Penstemon seed will roll freely when the paper plate is swirled.  Having a greater specific gravity than the powdery chaff, it tends to congregate and roll into the flutes at the edge of the plate where I gently brush it into another paper plate and then package it in a paper envelope.

If the seed is too large to go through the fine-mesh strainer, I dump the strainer contents (after rubbing) onto a paper plate and swirl the plate, blowing gently on any remaining pieces of chaff.  

The remaining seed and crushed capsules that I had set aside on the other paper plate are processed similarly, the only difference being that I may have to use an intermediate strainer to get more of the crushed capsules removed before I do the final seed rubbing and plate-swirling.

I have used this method on Penstemon seed for about 12 years.  Rubbing off the outer coating does not adversely affect the viability or length of storage of the seed as I have often germinated seed cleaned in this fashion that was up to 8 years old.