Cleaning and Drying Seed

[Tucson Grower]

I use commercial bagged silica sand, because it is basically clean and nearly sterile, also because I keep it available for some of my other projects. I once lived near, where some is mined, in Oceanside, CA.

Silica sand: I use a mix of #16 grit, coarse and #90 grit, fine. The fine sticks to anything somewhat moist, and the coarse helps it all come off the seed once they're drier. They're also pretty good at warming up in the sun.

The #90 grit will pass through window screen, and the #16 grit through, #8 hardware cloth. Of course this technique can be used for many seed, with adjustments for seed size. Unless, of course they're the size of #90 grit sand or smaller -- like Stinging Nettle (Urtica dioica), Butterfly Bush (Buddleja davidii), or Mullein (Verbascum thapsus), to name a few with tiny seed.

Place your target seed in a flat, clean container. I often use paper plates. Add sand to cover the seed, then mix gently to get seed thoroughly covered with sand. Place in sun until thoroughly warmed, then gently knead the mixture, focusing on getting the sand to gently rub the seed clean. Additional sun warmings may be needed. Once the seed looks as clean as you'd like, using the screen, separate the sand/chaff from the seed, rubbing the seed gently against the screen can remove stubborn chaff.

Then place the seed in paper envelopes with appropriate info written on them, place the envelopes of seed into airtight containers, plastic zip-loc bags, or glass canning jars, add an appropriate quantity of active indicator desiccant -- wait. If the desiccant becomes exhausted, replace it with fresh. Repeat until desiccant remains active. You now know your seed is clean and dry, ready for normal or long term storage.

[heavyhitterokra]

Tucson Grower,
Thanks, for the seed-saving tips and tricks. I never would have thought of that in a thousand years.

[Tucson Grower]

Of course, many seed, like okra, corn or beans; only need to be removed from their pod or cob; then dried using the desiccant. And smaller seed like pepper or tomato, wouldn't usually need the coarser sand (though it wouldn't hurt). I began by using the sand to help clean melon/squash seed, before desiccant final drying.

[Tucson Grower]

They generally have two kinds of indicator desiccant. The one with an added tinge of blue, turning pink when exhausted, uses cobalt chloride as indicator, the one that is a golden orange when active and turns dark green when exhausted, uses methyl violet. Supposedly cobalt chloride is toxic and methyl violet is not. However, that is a point of debate. Regardless, these products aren't for human consumption, which would actually be how they are toxic. I don't eat any, and I'm still okay.

What I like best about the indicator desiccant is how it warns me that my seed might be compromised by humidity/moisture, if the desiccant becomes exhausted (absorbs its max limit of H₂O). I then know to quickly replace it with fresh desiccant. Also to check for any leaks in the "airtight" outer layer. 

[Tucson Grower]

Nope, I first place the seed in paper envelopes, place the envelopes in canning jars or individual zip-loc plastic bags, community zip-loc bags (for more than just a single seed envelope) or whichever airtight container the paper envelopes of seed are placed in. These paper envelopes come in different sizes to suit the seed, they're also available in various colors. The colors help to code the seeds for sorting. I use black envelopes for anything that is intrinsically poisonous, like Castor Bean. You could use various colors for your own sorting purposes. The paper envelopes permit the desiccant to dry the seed through the paper. This keeps the seed apart from the desiccant. If you were to put the seed and desiccant together, it would make it much more difficult to change-out the desiccant once it is full of water and needed to be changed. Also, more difficult to separate the seed from the desiccant when you wanted to plant it.

It sounds kinda complicated, but once you have decided how you'll work it, for you. It goes much smoother, from there. For instance you could choose the color red for various tomato seed, or orange for chile pepper - for examples.

[Tucson Grower]

Okay, I am sometimes lazy, and take shortcuts. I will sometimes place desiccant in Organza Bags, then pull the drawstrings tight, then put a single cross-over knot in the drawstrings to help keep the desiccant where I want it. The desiccant must always be visible, so you know when it needs replaced/recharged. I'll then place this bag of desiccant into a large zip-loc or canning jar, with multiple seed packets, even seed stored in zip-loc bags, as long as the seal is not completely closed - the desiccant can draw out the moisture in the seed.

Indicating desiccant is also sold in small translucent packets and small capsules - these, or ones made with small organza bags, would work fine, inside a ziploc with seed. As long as it can contact the air where the seed is, and it is visible (so it can be observed for its color change), it should work fine.

[Tucson Grower]

I usually use between a teaspoon and a tablespoon's worth, per seed packet. It also depends on the volume of seed being protected from untimely moisture. Also how much moisture remains in the seeds, before desiccant drying. That's what I like most about the indicator desiccant. It's indicator function, answers the moisture question for me. Once I first assemble the seed/desiccant, I keep an eye on it, sometimes the desiccant is exhausted quickly (the seed likely still had too much moisture in them). Eventually (usually after just one change of desiccant), the desiccant will remain active. Most times there isn't enough moisture remaining in the seeds to even exhaust the desiccant.

It is likely that frozen seed would do just fine, sans desiccant. But it would defeat the main purpose of having indicator desiccant. The indicator is a visual warning that the seed might be compromised by moisture. If it weren't there, it couldn't provide that essential warning.

There are, however, humidity indicator cards, that use the same color-changing compounds that are used in the desiccant. They could likely work well if you wanted to separate the seed and desiccant when freezing, but still wanted a warning if the seed were possibly moisture compromised. The humidity indicator cards, for me, were just an unnecessary, extra expense, though I purchased a few to try, I couldn't justify the expense.

[Tucson Grower]

I just discovered some additional info about using desiccant to dry seed. It has been working okay for me, 'til now, but I think I'll make some tweaks to my technique, according to the additional info I found at Southern Exposure Seed Exchange. See link above. Especially concerning pea seed.

[Deleted]

Good stuff. I ordered some mylar bags and dessicate packets and thought to come here and refresh my memory.

It would be easy for me to color code envelopes. Really like that idea