Article by GreenZone
Seeds may look inert, but viable seed is actually a tiny living plant surrounded by a small but essential quantity of nutrients. Seeds are perishable under ordinary conditions; extremely high temperatures, above 120 degrees F, can kill them outright. Otherwise, the tiny plant continues dormant, very slowly consuming the stored nutrients for as long as they last. When that reserve is gone, the seed is no longer viable. Knowing how to handle and store seeds assists the embryonic plants in making their reserves last as long as possible, which increases the shelf life of the seeds. Your home already possesses most of the tools and conditions necessary for near-optimal storage of seeds, provided proper practices are followed. This article offers some pointers that can be useful to gardeners in their efforts to maximize the viability of seeds held for later use.
What is a seed bank?
Every gardener has a seed bank, whether it’s recognized by that name or not. Have leftover seeds from previous seasons? Or packets bought at closeout for next to nothing? How about that squash you plan to save the seeds from, or those snap beans that matured on the plant? Any seed, reserved for later use is, in fact, a seed bank. Even weed seeds in the soil, lying in wait until who-knows-when, constitute a seed bank, albeit one you’d rather see overdrawn!
So what sets one seed bank apart from another? The answer, in a word, is “intent.” From the lofty goals of the Svalbard Seed Bank in Norway, to that shoebox full of seeds under the bed, to nature’s seed bank in the soil, every seed bank has its unique purpose and is managed accordingly.
Why keep a seed bank?
Why bother keeping a seed bank at all? Why not just buy seeds fresh every spring? I asked Ira Wallace of Southern Exposure Seed Exchange that question. Her answer should come as no surprise to most heirloom enthusiasts.
“I think that one of the main reasons is the changes in the seed industry. There’s a lot of consolidation.” As big companies gobble up smaller ones, they tend to discontinue what they regard as unprofitable or superfluous varieties. If you find that you have a favorite variety, she explains, “you can’t count on being able to buy it in the future. If they stop growing them, the seed is not available to anyone.” Anyone who hasn’t squirreled away the discontinued variety, that is. “It’s nice to have what you want right there at hand.”
Also, with heirloom/open pollinated varieties, you can save seeds produced in your own garden, carrying them over into future years. That’s something you can’t do with hybrids, which don’t breed true. These need to be purchased anew every year, which is great for business, but doesn’t suit thrifty gardeners and farmers. And saving seed has additional advantages. By saving only seed from individual plants that performed best under your unique conditions, and according to your unique standards, over time you could develop locally-adapted varieties, superior to off-the-shelf strains. After all, that’s what gardeners had always done, up until the advent of the organized seed trade a couple of centuries ago.
But whether you choose to save seed, or prefer just to purchase it, store it correctly until you’re readyto use it. Often a packet contains far more than you’d care to use in a single season. For example, a packet of tomato seeds might contain 25 seeds. That could yield at least 20 tomato plants, all of the same variety. That’s a lot of tomato plants for most gardeners, especially if they enjoy trying different varieties! The obvious solution is to plant only a few, and store the remainder for another season.
How to store seeds safely…
Seeds store best in conditions that do not encourage germination, and that do not cause the embryonic plant to exhaust its stored nutrients. For the vast majority of seeds, germination is stimulated by a moist and relatively warm environment. Therefore, to delay germination and maintain vigor, store seeds in a cool, dry location. Ira advises would-be seed bankers to “look around and find where in their house is a good place to have them. The first thing is to have them in a cool, dry place.”
How cool is cool, and how dry is dry enough? A rule of thumb is to store seeds where the temperature plus the relative humidity equal one hundred. For example, if a room is 70 degrees Farenheit, a relative humidity of up to 30 percent is good, since 70+30=100. So, happily, it works out that conditions that suit people are pretty good for seeds as well. Most seeds will store for several years in ordinary indoor conditions. The table at the end of this article shows what can be expected for a number of common types, in ordinary household conditions, according to a Colorado State University publication.
Room Temperature Storage
If your intent is to store seed for use within a few years, then storage at room temperature will be adequate. All that remains is to select containers and a location for the seed bank.
Be sure to pick a spot that follows the formula. Don’t store your seeds in a bathroom closet (too humid) or near a direct source of heat, such as a sunny window or near a heater. Instead, try to identify the coolest and driest place in the home. That shoebox under the bed isn’t such a bad idea–it’s usually cooler near the floor. A closet in an unheated spare room is great too. And seeds keep best when stored out of bright light.
Choice of containers is easy. The packets that the seeds were sold in work just fine, and are easy to keep organized. If home-saved seed are being stored, plastic zip-lock bags are good, but jars are better. (But be certain that freshly harvested seed has dried adequately before storage!) The entire seed bank can be kept in a bag, box, or ice chest.
A few packets of silica gel, changed or reactivated annually, completes the picture. Silica gel is the stuff that comes in little packets, included in packaging when you buy a new electronic device, and many other products. The silica gel draws moisture from the air around it, and traps it. The material can absorb up to 20 per cent of its own weight in water. Additionally, silica gel absorbs ethylene gas, a waste product of the seed’s respiration. In a very close environment, ethylene gas can build up to toxic levels and cause premature death of the seed.
Avoid storage pests, which can ruin an otherwise well-maintained seed bank in short order! Guard against mice, especially in the fall, when the creatures seek shelter from the coming winter. They try to set up housekeeping indoors, and your seed bank is an attractive stockpile of food to them. Nobody wants them around, and control measures will already be in place as needed, but remember that they will be attracted to your seed bank nearly as much as they are drawn to the kitchen.
Other pests are more insidious–less apt to be noticed and harder to control. Numerous types of moths and weevils love your seed bank quite as much as you do, so be watchful. Be careful to avoid bringing them in, especially with home-saved seed, since these are vulnerable during the drying process. Remove infested lots promptly. If insects do appear, they can usually be eradicated by freezing at 0 degrees F. for ten days–you could treat the entire seed bank that way if necessary, with the exception of a few exotic tropical species. Mothballs, if you don’t object to them, may discourage a range of pests. Organic deterrents include cedar or peppermint oils, various herbs, and diatomaceous earth. Each method has its adherents, and no doubt each method has been known to fail. That makes it worthwhile to check the seed bank periodically, so you can respond promptly.
Long-term storage
The simple measures outlined above are adequate for short-term storage. But what if a longer shelf life is desired? Some people, especially those with something to sell, advocate canning, freeze-drying or vacuum-packing the seeds, but that is not really necessary, though all do work quite well. Storage in the refrigerator or freezer is a simpler answer, and again, is readily available in the home. How long will they last? Ira said that “We have some seeds that Jeff [Jeff McComick, founder of Southern Exposure Seed Exchange] collected back when SESE had just started [in the 1980's]. We pulled them out, and they germinated around 40 per cent!” I was told by a British seedsman that he was still selling seeds that had been freezer-stored since the Seventies! Authorities agree: seed stored in the freezer last a very long time–decades in many instances!
For freezer storage, it’s imperative that the moisture content be very low prior to freezing, otherwise the seeds may be damaged. Homegrown seed should be dry enough that it snaps rather than bends (in the case of flat seeds like squash or melons), or is very hard in the case of other types. Commercial seed is dried down to the proper moisture content, about 8 per cent, but if it’s been exposed to humid conditions it may have taken up some moisture. In that case, take steps to reduce the moisture content somehow. One way is to place the seeds in a warm location (100 degrees is recommended) and set a small fan to circulate air around the seeds for a few hours.
Once the seed is fully dried, place it in closed containers and include silica gel. You can even purchase silica gel that changes color when saturated, indicating at a glance if the moisture level has been reduced sufficiently. Thus it can be used both to achieve the final drying of seeds as well as acting as an ongoing indicator that proper low levels of moisture are being maintained. If the color of the granules tells you that the gel has reached saturation, simply remove the granules and replace with fresh ones. Saturated silica gel can be refreshed by baking in a low oven, which drives out the moisture and allows the granules to do their work yet again. Be sure to follow manufacturer’s directions.
Remember to avoid exposing very cold seed to warm room air. Otherwise, moisture condenses from the air and collects around the seed, just as it collects on a cold glass of lemonade on a hot day. So always remove the container from the freezer several hours before opening, which allows the seed to come up to room temperature, eliminating the problem.
If freezer storage is not preferred, drying seed to extremely low moisture levels (1-3 per cent) has been shown to increase shelf life 4-16 times over ordinary room-temperature storage. Curing seed fully, under moving air at 100 degrees F., is the way to start. Silica gel or other dessicants are mandatory in this case, utilizing some form of the product with the moisture-indicating color change. Granules are simply cycled through the closed container repeatedly and replaced until no further color change is noted, and periodically thereafter to maintain low levels. Most vegetable seeds tolerate this treatment. It’s been shown to be as effective as freeze-drying, and is much simpler to do. A few of the larger seed types, such as squash, may be damaged by such extreme dessication. Also, beans and peas, and no doubt some other types, may develop so-called “hard-seed.” This means the seed is more deeply dormant, and may require what Ira calls “heroic means” to induce germination. Otherwise it takes longer to germinate, sometimes a lot longer, but with ordinary garden types, usually a 2-3 weeks exposure to higher humidity prior to sowing will be adequate.
Studies show that the best containers for long-term storage, in the freezer or out, are the so-called Scotch jars–the canning-type jars that have a metal bracket, glass stopper, and rubber gasket. These jars exclude all moisture. Jars with screw-type fittings may allow some moisture inside eventually, since the lids loosen over time, due to the expansion-contraction cycle that accompanies even slight temperature variation. Still, ordinary jars with screw-on lids can be employed, and will safely store banked seed for many years, particularly in conjunction with silica gel. Plastic allows moisture infiltration over time, and isn’t considered adequate for very long storage periods, although it’s fine for ordinary storage requirements.
Organization
Organizing your personal seed bank need not be complicated, but must be adequate for your purpose. If you’re using original packets, alphabetizing is easy. Or you could segregate by types, with all your tomato seeds grouped together, all the beans together and so on. What matters is that you can find the seeds when you want them.
If you have numerous varieties, a list, kept current, saves a lot of time. It can also strengthen your resolve–if you know those Wando peas are there somewhere, you’re more apt to keep looking until you find them!
If your seeds are stored in jars, baggies, etc, pay attention to labeling. Labels should be legible and contain whatever information is important to you. Variety name of course should be included, and possibly the year grown. It’s wise to include a label inside the container as well, especially for long-term storage. Adhesive labels peel away and felt pen sometimes rubs off, so a label inside the container is a worthwhile precaution.
Conclusion
Seeds come to us already set up to store until conditions are favorable for growth. By giving nature a little encouragement, we can store them for a very long time. So develop your personal seed bank. Take care of your seeds, so they can take care of you!
GreenZone (not his real name) lives, works and gardens in the Missouri Ozarks. An heirloom seed saver since 1982, he now offers heirloom plants in season on his website, www.abundantacres.net.
©2010.