Seed Storage Mistakes Everyone Makes And Doesn't Realize It

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Do you remember the moment you bit into the juiciest melon you had grown and thought, "I must save the seeds for next year?" Turns out, you could, as stored seeds can typically remain viable for nearly five years. The cherry on top is that you can pull a similar stunt on the half-filled seed packets left behind after an overzealous stint of spring mail orders — even for those nearing or past their "sell-by" date. Gardeners with limited planting spaces could also benefit from such seed storage in the case that they don't use the entire packet during a single season.

However, to ensure germination and planting success in forthcoming seasons, there are certain seed storage missteps you should avoid. For instance, not all kinds of seeds can or should be saved — we're looking at you hybrids, diseased, and pelleted seeds. Even when you've got the pulse on the right kind of seeds to harvest from your garden and replant, paying attention to storage conditions or the CDD rule is especially important. Standing for "cool, dry, and dark", CDD spells out the typical conditions seeds require during dormancy. Mess up on one, and you can expect to meet germinated seeds when you empty your stored packets. Since you don't want that happening, here's a quick roundup of common seed storage mistakes gardeners keep making. Steer clear of them, and your plants should be as productive as their age allows (germination rates gradually begin to fall, the longer the sowing is delayed).

If you've ever wondered why your seed-grown pumpkins taste funny when they were perfectly zestful last year, chances are they might've cross-pollinated. Certain vegetables, including corn, cucurbits, and vine crops, tend to exchange genetic material with other closely related plants. This can create seeds that might not carry their original characteristics. More often than not, such cross-fertilized seeds taste mightily inferior, defeating the purpose of collecting and storing them.

You might face similar issues with hybrid varieties. Many vegetables are cross-bred for superior characteristics, such as improved disease resistance and yields. However, to maintain these improved traits, parent plants must be cross-bred physically every year. In other words, the hybrid vegetables themselves — usually marked "F1," "hybrid," or a combination of both on seed labels — either produce unproductive seeds or seeds that are unlike their parents. For this reason, storing them makes little sense unless you're looking for a gardening adventure and aren't limited by patenting.

Instead, focus on saving seeds from open-pollinating varieties, which grow to be pretty similar to the original parent plant as long as they cross-pollinate with similar varieties or cultivars. If they cross with different varieties, though, you'll run into the same issues as with hybrid seeds, so make sure you plant them further away from differing plants. 

Many gardeners underestimate how many seeds they need to maintain the same garden size the following year. This can be a mistake since seeds exhibit varying germination rates and viability across varieties. For instance, vegetables like okra, celery, pepper, and carrots fall in the ballpark of 50% to 60%, with overall viability not going past three years, even when they're stored properly. Onion, parsley, and leek fare even worse, usually not lasting beyond a couple of years. In contrast, cucumbers, lettuce, peas, and turnips hit germination rates of 80% and maintain their productivity for five years or more. Also, germination rates naturally decline with storage time, further reducing expected yields.

Due to this, you must err on the side of abundance, especially for short-lived seeds, and avoid keeping them for prolonged durations. Make sure to carry out a viability test for seeds saved for over a year with this simple paper towel trick. Place at least 20 seeds on a moist paper towel, fold it over, and put the towel inside a plastic bag. After poking a few holes, keep the plastic atop your refrigerator and examine the seeds after a week. If over half of them have germinated, your seeds are viable. Otherwise, you'll need to sow them thickly or scramble last-minute for replacements. 

Eager to preserve your favorite varieties, you may sometimes overlook signs of disease on your plants. This can be a huge mistake because plant viruses can hide inside seeds. As such, they might materialize later in sown seedlings, leading to a widespread infection. This is quite common for tomatoes, especially in places with a history of disease — though flowers aren't untouched by this phenomenon either. When saving seeds from fruits, make sure the fruit hasn't been damaged by insects or left to rot on moist ground. Otherwise, these seeds can spread diseases to their companions once stored, making the whole lot unusable.

So, be careful of the plants you're saving seeds from. Make sure you choose the healthiest of the lot, ones that are growing well and producing plenty of flowers. On the off-chance you might have stored contaminated seeds, give them the bleach treatment. In this process, dilute 5.25% hypochlorite bleach, such as Alliance Chemical Sodium Hypochlorite, with water in a 1:4 ratio. Add a dash of liquid dish soap, stir, and dunk the contaminated seeds. Ensure they're floating on the surface for maximum contact and filter them out after a minute with a cheesecloth. Run cold water through the bleached seeds for 5 minutes, dry them, and store — or plant immediately if you can. Do note that this won't work adequately for bacterial cankers or pathogens that have moved past the surface coat and infected the seed. As a result, you may have to deal with lower germination rates.

Pelleted seeds — the rounded, colorful seeds used for planting carrots, lettuces, beets, endives, celeriac, and basil –  have a lot of benefits. They make sowing precise since they don't camouflage with the soil nor wash off as easily when it rains. Since they come glazed with a clay coating to enhance germination, they offer much better yields. They also feel meatier in hand — an attribute crucial for senior gardeners and children alike. However, you shouldn't store them, and here's why.

Pelleted seeds usually have a thin veneer that can split apart during storage. Once that happens, moisture can make its way inside the seed, kickstarting germination. Because of this, use up the packet of pelleted seeds in its entirety within the same growing season. However, if you need to store them, keep them in air-tight containers and avoid exposing them to sudden changes in humidity. Also, prioritize them in the next planting season, as storing pelleted seeds beyond a couple of years will lead to poor germination numbers later.

Another critical mistake gardeners make when starting their seed-saving journey is not drying the harvested seeds through and through before storing them. Moisture levels above 8% can result in seed degradation and may even turn the kernels into a hotbed for fungal pathogens (remember they like it cool and damp), rendering your seeds unusable. The exceptions to this rule are legumes like peas and beans, which don't have to be dried thoroughly. 

Air dry the selected seeds for one to three days  in a dry, ventilated spot. Don't forget to remove the pulp, or it'll crust over. Avoid keeping the seeds in direct sunlight, as temperatures exceeding 100 degrees Fahrenheit can cook them. If you can't wait that long, pop the seeds in a conventional oven and heat them to under 90 degrees Fahrenheit while keeping the door ajar. Or, you may subject them to a compact fan in a seed drying cabinet like BSROBOTIC's Mesh Drying Rack. In particularly humid climates, take two envelopes — one holding seeds and the other a silica gel (such as Dry & Dry's Reusable Desiccant Beads) — and place them in a glass container. They should dry down sufficiently in under two weeks, and you can remove the silica gel envelope after.

Not all plant seeds come off easily and may entail quite a bit of debris, including seed casings and fruit pulp. This chaff can readily absorb moisture, hurting seed viability, so it's important to remove it beforehand. Plus, it'll limit the required storage space needed. 

How you go about separating chaff from seeds will vary. In small quantities, you may simply pick off the seeds with tweezers, discarding the rest. Alternatively, you can place the harvested mass on a folded sheet of paper, laying the seeds and debris in the crease. Gently tilt the paper over a basket and tap it, letting the materials slide down slowly. The tapping will separate the seed from the chaff, and since the seed is heavier, it will fall out first, making it easier to collect. Another method is winnowing, which is key when cleaning seeds. It's when you use wind to separate heavier seeds from lighter chaff. To do this, set up a basic box fan and adjust it to its lowest settings. Place your harvested material in a basket and gently toss it in front of the fan. The light chaff will quickly blow away. However, these methods will not work for equally-weighted seeds and debris. For them, you can repurpose a colander as a sieve to separate seeds. 

Another area where you might mess up is storing thinly or softly coated seeds for too long. Essentially, a seed's outer coating protects it from harsh environmental conditions as well as moisture in the air, which would trigger early sprouting. Without it, it would either not survive the winter or would begin to germinate early, dying before spring.

Given this, you must account for the seed's hard coating before storing, and the thinner the coating, the faster it should be planted. Onions, alliums, lettuce, edamame, and parsnips should ideally be planted within a season or two. Even tree seeds like mango, avocado, jackfruit, durian, neem, mahogany, and rubber shouldn't be stored for long. In contrast, harder-coated seeds like hollyhock, sunflowers, marigolds, calendulas, and zinnias may be maintained for five years.

It's surprising how many gardeners rely on memory or makeshift methods while storing seeds, thinking they'll simply identify the plants once they start sprouting. Unfortunately, seedlings usually look the same, making it difficult to tag them until they begin maturing and rooting. So, save yourself some brain fog and make the effort to record crucial information about collected seeds while storing them.

After the seeds are sufficiently dry, slide them into a paper envelope and label them. Better yet, opt for resealable seed envelopes, such as Yelofesh's Small Resealable Seed Envelopes, that prompt you to record the type, variety, and year of collection. Recording the collecting time is important so you know which seeds can last for longer and can be planted later to make space for short-lived seeds (like corn, pepper, and parsley). You may also record any growth notes and germination rates to further decide if you wish to keep planting them or try out better varieties.

If you're just saving leftover store-bought seeds, put them back in their original packaging by folding or sealing the packet. These packets already carry all the critical information about variety, viability, and germination rates. To stay organized and keep track of planting seasons and crop rotations, group the seed packets in a metal seed bin by season, month, or family. Xbopetda's Metal Seed Saving Box is a good example. This will also pest-proof them against rodents.

While there are many clever ways to store the seeds you collect from your garden, including old medicine bottles, plastic bins, or used food cans, not all of them are suitable for long-term storage. This holds especially true if you plan on refrigerating the saved seeds, in which case good sealing is necessary to keep the seeds dry and healthy. That's why sandwich bags are usually a huge letdown, as they can collect moisture and promote germination. In contrast, their thicker counterparts, like polythene bags, may keep the seeds viable for upwards of two years with proper care. However, they might still experience sweating, especially if you haven't made sure that all air is out.

The best option would be to save your seeds in mason or glass jars, provided they've got good lids. They can keep the majority of the stored seeds viable even after five years. However, as they don't block out sunlight, you must ensure the jars are stowed in a dark spot. Spice shakers are other suitable alternatives, as are photo storage boxes, such as the Novelinks Transparent Photo Cases.

Don't place your stored seed containers on windowsills, sheds, the garage, or in front of air vents. This is because the seeds might take the changing temperatures as cues for seasonal changes and germinate prematurely. Worse, even after the cold temperatures are restored, they cannot return to dormancy. This might tank their viability, resulting in poor germination rates.

To sidestep such pitfalls, it's important to plan your planting schedule. If you've got a small batch of seeds that you can use within the following year or two, you may store them in any cool and dark space, including basements, kitchen cabinets, or pantries. However, to retain seed viability beyond two years, it's best to maintain temperatures between 32 and 41 degrees Fahrenheit. These can usually be found in regular refrigerators, but using sealed containers with tight lids is pivotal to avoid moisture condensation. The key is to ensure the sum of the temperature and humidity levels remains below 100% (for example, if the temperature is 40 degrees Fahrenheit, the humidity needs to be under 60%). 

That being said, while keeping seed containers in freezers is an option and may even keep them productive for nearly a decade, you must note that any power outages or accidental unplugs may render them useless. Also, when you're ready to use them, allow the containers to reach ambient temperatures before removing the lids.

Seeds, being seeds, soak up moisture whenever they can — no matter the pains taken to dry them before storing. That's why storing them in humid environments, like summer sheds or in non-air-tight containers in the fridge, can cause them to either rot or germinate. As you can see, neither outcome is welcome.

Ultimately, you must keep seeds in areas where humidity levels are below 60%. While this is easily achievable in dry climates, in other places it may become necessary to use additional desiccants. Luckily, there are plenty of options to choose from. A single silica gel packet, like Vbeijll's Color-Indicating Silica Gel Packets, work well in seed containers. Just remember to remove them after a few weeks to prevent over-drying.

Alternatively, if you've freshly opened a pack of powdered milk, you may add a few tablespoons of it to a cheesecloth and place it next to the seeds. It will wick any excessive moisture for the greater part of the year. White rice baked at 220 degrees Fahrenheit and sealed in a jar may also be used, with the seed packet placed inside afterward. 

Even a 1% drop in moisture can raise (and sometimes double) your seed's viable life. However, note that there are some plants, like milkweed, that require moist stratification, so this rule won't apply to them.