<\/p>\n\n\n\n
I grow a wide variety of crops (often several varieties of each one) every year, which means that I end up with a lot of half empty seed packets at the end of the growing season. Fortunately most seed remains viable for at least 3 years (even if just sitting in a drawer in your kitchen) so you can use up the rest of the packet the following year. A few kinds of seed (corn, onion, leek, chives and parsnip) are only considered dependable for 2 years, so you should try and use these up as soon as possible. Others (cabbage, chicory, endive, cucumber, squash and tomato) may last as long as 6-8 years. <\/p>\n\n\n\n
The exact length of time a\nseed will remain viable is determined by how it is stored. Seeds are living\nplants in a much reduced form and have to respire to maintain life processes. This\nslowly depletes their food reserves, so vigor declines until the seed runs out\nof food and is no longer able to germinate (this is why 5 year old seed isn\u2019t\nusually as vigorous as one year old seed). <\/p>\n\n\n\n
If seed is to remain in good\ncondition for future use, it must be stored properly. If you are planning to\nuse the rest of the seed in the following year, all you need to do is keep them\nin a dry, cool place. If you want them to survive as long as possible you must\nkeep them very dry and very cool. This means drying them thoroughly (put them\nin a glass jar with a moisture absorbent such as silica gel) and then keeping\nthem in a place that remains cool even in summer. For longest possible storage\nthey may be kept in a freezer, though any seed you store in this way must be\nvery dry, otherwise moisture in the seed may freeze and damage it. <\/p>\n\n\n\n
Garden centers often sell\noff year old seed packets cheaply when the new seed arrives in February or\nMarch and this can be a good way to save a little money and try some new\nvarieties. It should still be good for at least another year and often a lot\nlonger (just be aware of which seeds are long lived and which aren\u2019t). The best\ndeal is seed that comes in packets lined with aluminum foil, as this keeps the\nseed very dry and extends its life considerably (I\u2019ve had good germination from\n12 year old lettuce seed packed in foil).<\/p>\n\n\n\n
Factors in seed storage<\/strong><\/p>\n\n\n\n The factors responsible for\nseed losing its vigor are the same ones necessary for seed germination:\nmoisture and warmth. They speed up seed metabolism (in preparation for\ngermination) causing it to respire at a faster rate and use up its reserves of\nfood more quickly . This is why it is not good to leave seed packets in warm\nhumid places such as the greenhouse (and never let them get wet.)<\/p>\n\n\n\n Moisture is the most\ncritical factor in shortening a seeds life span. Seeds absorb moisture from the\nair very readily and their moisture content fluctuates with humidity. In very\ndry air it may be as low as 5%, while in very humid air it could be as high as\n14%. For every 1% rise in the moisture content of a seed (above 5%) its storage\nlife is halved. This means that for longest life you should keep your seeds as\ndry as possible. If they get wet they lose their viability very rapidly.<\/p>\n\n\n\n High temperature shortens\nseed life in the same way as moisture, by increasing the rate of respiration.\nFor every 18\u00b0 rise in temperature above 32\u00b0F the storage life of seed is\nhalved. This isn\u2019t quite as critical as moisture (seeds keep very well when\nsimply stored in unopened foil packets), but the two have a synergistic effect.<\/p>\n\n\n\n Relative humidity should be\nlow: 40% is good. There is a rule of thumb that temperature and humidity added\ntogether should be less than 100. In low humidity areas the seed may dry\nsufficiently in the open air, in which case you just need to ensure that it stays dry.<\/p>\n\n\n\n Seed Longevity<\/strong><\/p>\n\n\n\n How long seed will remain\nviable at room temperature and average humidity depends on the species. The\nnumbers in the table below are only approximations, mostly useful for\ncomparison. Seed longevity isn\u2019t very predictable however and they often last\nlonger than you might expect (or longer than they should). <\/p>\n\n\n\n Generally it is better to\ngrow out a batch of seeds every few years (the exact time depending upon its\nestimated longevity), rather than try and save seed for a long period.<\/p>\n\n\n\n Drying seed<\/strong><\/p>\n\n\n\n Seeds must be very dry if\nthey are to remain in good condition for any length of time. The safest way to\ndo this is to put the seed packets in a sealed jar with a desiccant. You can\nuse dry powdered milk (from a freshly opened packet), but silica gel is much\nbetter. This is usually treated with cobalt chloride, to make blue crystals\nthat turn white when they absorb moisture.<\/p>\n\n\n\n Drying the seeds is simple\nenough. Measure out an amount of silica gel equal in volume to the amount of\nseed. This is roughly an ounce of seed to one tablespoon of silica gel (or 3\ntablespoons of fresh powdered milk). Seal it into the airtight jar with the\npackets of seed. When the silica gel turns white from absorbing moisture, it\nshould be replaced with fresh gel (do this quickly so as not to admit too much\nmoisture). The white gel can then be re-dried for later use. Repeat this\noperation as necessary until the gel in the jar no longer turns white. You\nshould then change the gel routinely every six months or so, to ensure the\nseeds are kept dry. When the seeds are thoroughly dry they will shatter when\ncrushed, rather than simply being flattened.<\/p>\n\n\n\n It is possible to dry seeds\nslowly in a cool (100\u00b0F max) oven for up to 6 hours. You have to take extreme\ncare not to overheat them though, as this will definitely kill them.<\/p>\n\n\n\n Seed storage ideas<\/strong><\/p>\n\n\n\n If you want to store seeds\nfor any length of time you must keep them dry and cool. There are a number of\nways to do this, depending on how long you want to keep them. Obviously if you\nare only going to keep the seed until the next spring planting season, then\ngood storage conditions aren\u2019t as important as if you are starting a seed bank\nand hope to store them for 50 years.<\/p>\n\n\n\n Commercial paper packaging\ndoesn\u2019t do anything to protect the seed. This doesn\u2019t matter if the seed is\nfresh and is to be used promptly, but means that the seed will lose viability\nat the normal rate when stored at room temperature and humidity (see the table\nbelow).<\/p>\n\n\n\n The best commercial seed\npackaging is the aluminum foil pack that keeps out all moisture until opened. I\nrecently germinated some 20 year-old foil packed kale seed that grew very well,\neven though stored at room temperature and humidity. Once the foil packet is\nopened the seeds start to deteriorate at the normal rate, unless you quickly\nre-seal the packet with tape.<\/p>\n\n\n\n Seeds last longer if stored\nin the refrigerator at 35 – 40\u00b0F, however they must be kept in an airtight\ncontainer, as refrigerators tend to be very humid.<\/p>\n\n\n\n The best way to store seeds\nlong term is to dry them with a desiccant (see below) and then freeze them to\nabout 15\u00b0F. Remember the colder you store the seeds the longer they will live.\nThe seed must be thoroughly dry before it is frozen though, as undried seed may\nbe damaged or killed by ice crystals forming inside it.<\/p>\n\n\n\n Once seed is in storage it\nis best to leave it undisturbed. Opening a container and removing seed lets in\nmoisture (and if it is cold enough may result in condensation on the seed).\nSeveral rounds of freezing and thawing are not good. In this situation you may\nwant to have several packets of a variety, so you can take some out without\naffecting the rest.<\/p>\n\n\n\n For very long term storage\nyou can vacuum seal the seed in a plastic bag and store that in the freezer in\na glass jar full of desiccant (plastic itself may gradually allow moisture to\npass through it).<\/p>\n\n\n\n Whenever you save seeds it\nis very important that each lot be labelled clearly and that it can\u2019t wear off,\nor otherwise disappear over time.<\/p>\n\n\n\n Storage containers<\/strong><\/p>\n\n\n\n Any container can be used for seed storage, so long as it is moisture proof , airtight (some plastics are actually permeable) and pest proof. The most popular container is a screw top glass jar with a rubber gasket (cut from an old inner tube) in the lid. Seal-able plastic freezer bags can also be used, if you suck out the surplus air before sealing. Ideally you will put an open container of silica gel in the container so you can see its color (if this changes to indicate it has absorbed moisture, you can replace it) Always remove the seeds and re-seal the container as quickly as possible).<\/p>\n\n\n\n Seed longevity table<\/strong>
<\/strong>Any list of seed longevity is only an estimate, because of all the variables involved. <\/p>\n\n\n\n\n Seed Longevity in years<\/strong>\n \n <\/td><\/tr> \n Crop\n \n <\/td> \n Mini-\n \n <\/td> \n Aver-\n \n <\/td> \n Maxi-\n \n <\/td><\/tr> \n Alyssum\n <\/td> \n 3\n <\/td> 4 <\/td> \n 5\n \n <\/td><\/tr> \n Amaranth\n \n <\/td> \n 4\n \n <\/td> \n 6\n \n <\/td> \n 8\n \n <\/td><\/tr> \n Artichoke\n \n <\/td> \n 4\n \n <\/td> \n 4\n \n <\/td> \n 4\n \n <\/td><\/tr> \n Arugala\n \n <\/td> \n 2\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Asparagus\n \n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td> \n 3\n \n <\/td><\/tr> \n Barley\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Basil\n \n <\/td> \n 2\n \n <\/td> \n 4\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Bean, Bush \/ Pole\n <\/td> \n 2\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Bean, Fava\n \n <\/td> \n 2\n \n <\/td> \n 4\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Bean, Lima\n \n <\/td> \n 2\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Bean, Mung\n \n <\/td> \n 2\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Bean,\n Scarlet Runner\n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Bean, Soy\n \n <\/td> \n 2\n \n <\/td> \n 4\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Beet \n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td> \n 8\n \n <\/td><\/tr> \n Bok Choy\n \n <\/td> \n 4\n \n <\/td> \n 6\n \n <\/td> \n 9\n \n <\/td><\/tr> \n Broccoli \n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Brussels Sprout\n \n <\/td> \n 2\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Buckwheat\n \n <\/td> \n 1\n \n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td><\/tr> \n Cabbage \n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td> \n 10\n \n <\/td><\/tr> \n Carrot \n \n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Cauliflower\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Celery \/ Celeriac\n <\/td> \n 2\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Celtuce\n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Chamomile\n \n <\/td> \n 2\n <\/td> \n 3\n <\/td> \n 4\n <\/td><\/tr> \n Chard \n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Chervil\n \n <\/td> \n \n <\/td> \n 1\n <\/td> \n \n <\/td><\/tr> \n Chickpea\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Chicory\n \n <\/td> \n 4\n \n <\/td> \n 6\n \n <\/td> \n 8\n \n <\/td><\/tr> \n Chinese Broccoli\n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Chinese cabbage \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td> \n 7\n \n <\/td><\/tr> \n Chives\n \n <\/td> \n 1\n \n <\/td> \n 2\n \n <\/td> \n \n <\/td><\/tr> \n Cilantro\n \n <\/td> \n 2\n \n <\/td> \n 4\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Collards\n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Corn \n \n <\/td> \n 1\n \n <\/td> \n 2\n \n <\/td> \n \n <\/td><\/tr> \n Cornsalad\n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td> \n 7\n \n <\/td><\/tr> \n Cosmos\n \n <\/td> \n 3\n <\/td> \n 5\n <\/td> \n 6\n <\/td><\/tr> \n Cowpea\n \n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td><\/tr> \n Cress, Garden\n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td> \n 9\n \n <\/td><\/tr> \n Cucumber\n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td> \n 7\n \n <\/td><\/tr> \n Dandelion\n \n <\/td> \n 1\n \n <\/td> \n 2\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Dianthus\n \n <\/td> \n 2\n <\/td> \n 3\n <\/td> \n 4\n <\/td><\/tr> \n Dill\n \n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Eggplant\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Endive\n \n <\/td> \n 5\n \n <\/td> \n 7\n \n <\/td> \n 10\n \n <\/td><\/tr> \n Fennel\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Flax\n \n <\/td> \n 1\n <\/td> \n 2\n <\/td> \n 3\n <\/td><\/tr> \n Kale\n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td> \n 7\n \n <\/td><\/tr> \n Kohlrabi\n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td> \n 7\n \n <\/td><\/tr> \n Lambs Quarters\n \n <\/td> \n 4\n \n <\/td> \n 6\n \n <\/td> \n 8\n \n <\/td><\/tr> \n Leek\n \n <\/td> \n 1\n \n <\/td> \n 2\n \n <\/td> \n 4\n \n <\/td><\/tr> \n Lemon Balm\n \n <\/td> \n 2\n <\/td> \n 3\n <\/td> \n 4\n <\/td><\/tr> \n Lettuce \n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Luffa\n \n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Marjoram\n \n <\/td> \n 1\n \n <\/td> \n 2\n \n <\/td> \n \n <\/td><\/tr> \n Melon\n \n <\/td> \n 1\n \n <\/td> \n 2\n \n <\/td> \n 4\n \n <\/td><\/tr> \n Millet\n \n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td><\/tr> \n Morning Glory\n \n <\/td> \n 2\n <\/td> \n 3\n <\/td> \n 4\n <\/td><\/tr> \n Mustard\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Nasturtium\n \n <\/td> \n 3\n <\/td> \n 4\n <\/td> \n 5\n <\/td><\/tr> \n New\n Zealand Spinach\n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Oat\n \n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td><\/tr> \n Okra\n \n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Orach\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Oregano\n \n <\/td> \n 1\n <\/td> \n 2\n <\/td> \n 3\n <\/td><\/tr> \n Parsley, Hamburg\n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Parsnip\n \n <\/td> \n 1\n \n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td><\/tr> \n Pea\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Peanut\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Pepper\n \n <\/td> \n 2\n \n <\/td> \n 4\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Poppy\n \n <\/td> \n 2\n <\/td> \n 3\n <\/td> \n 4\n <\/td><\/tr> \n Potato\n (True seed)\n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td> \n 8\n \n <\/td><\/tr> \n Quinoa\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Radish\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Rhubarb\n \n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td><\/tr> \n Roselle\n \n <\/td> \n 2\n <\/td> \n 3\n <\/td> \n 4\n <\/td><\/tr> \n Rosemary\n \n <\/td> \n \n <\/td> \n 1\n <\/td> \n \n <\/td><\/tr> \n Rutabaga\n \n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td><\/tr> \n Sage\n \n <\/td> \n 1\n \n <\/td> \n 2\n \n <\/td> \n 4\n \n <\/td><\/tr> \n Salsify\n \n <\/td> \n 1\n \n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td><\/tr> \n Savory \n \n <\/td> \n 2\n <\/td> \n 3\n <\/td> \n 4\n <\/td><\/tr> \n Seakale\n \n <\/td> \n 1\n \n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td><\/tr> \n Sesame\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Shallot (seed)\n \n <\/td> \n 1\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td><\/tr> \n Shungiku\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Sorrel\n \n <\/td> \n 2\n \n <\/td> \n 4\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Spinach\n \n <\/td> \n 2\n \n <\/td> \n 4\n \n <\/td> \n 6\n \n <\/td><\/tr> \n Squash\n \n <\/td> \n 3\n \n <\/td> \n 6\n \n <\/td> \n 8\n \n <\/td><\/tr> \n Stevia\n \n <\/td> \n \n <\/td> \n 1\n <\/td> \n \n <\/td><\/tr> \n Strawberry\n \n <\/td> \n 1\n \n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td><\/tr> \n Sunflower\n \n <\/td> \n 3\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Thyme\n \n <\/td> \n 2\n <\/td> \n 3\n <\/td> \n 4\n <\/td><\/tr> \n Tomato\n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td> \n 7\n \n <\/td><\/tr> \n Tomatillo\n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td> \n 7\n \n <\/td><\/tr> \n Turnip\n \n <\/td> \n 2\n \n <\/td> \n 3\n \n <\/td> \n 5\n \n <\/td><\/tr> \n Watercress\n \n <\/td> \n 2\n \n <\/td> \n 5\n \n <\/td> \n 9\n \n <\/td><\/tr> \n Watermelon\n \n <\/td> \n 3\n \n <\/td> \n 6\n \n <\/td> \n 8\n \n <\/td><\/tr> \n Wheat\n \n <\/td> \n 4\n \n <\/td> \n 5\n \n <\/td> \n 6\n \n <\/td><\/tr><\/tbody><\/table><\/figure>\n","protected":false},"excerpt":{"rendered":"