Just long enough for the seeds to swell but not so long that they might begin to sour and rot. Overnight is usually good. Many sources recommend 8-12 hours and no more than 24 hours. Again, too much soaking and the seeds will start to decompose.
Soaking seeds supplies your plants a jump start right at the beginning of their lives. The water both softens the seed shell and supplies water to the seed interior.
By soaking the seed, it enables the new growth from the inside to push through the hard shell and grow. The seeds that could benefit from a good soaking include: corn, pumpkin, beans, chard, beets, and peas. The seeds you shouldn't soak include: carrots, lettuce, radish, celery, turnips, and spinach.
Common questions at this point include “How long should seeds be soaked?” and “Can you over soak seeds?” Yes, you can over soak seeds. Too much soaking in water and a seed will drown. It is recommended that you only soak most seeds for 12 to 24 hours and no more than 48 hours.
Some seeds take a long time to germinate, and seed soaking can help to speed up the process. By soaking seeds in lukewarm water for 8-12 hours (some can go up to 24 hours, but never more than that), you help the seed to break dormancy and germinate faster.
One method to check for seed viability is the water test. Take the seeds and place them in a container of water. Let the seeds sit for 15 minutes. If the seeds sink, they are still viable; if they float, discard, because they probably will not sprout.
Make sure to strain and rinse the nuts or seeds after soaking to eliminate the residual water which contains the absorbed enzyme inhibitors and toxic substances. Once you have given them a good rinse, enjoy them immediately or store them in your refrigerator for later.
Just long enough for the seeds to swell but not so long that they might begin to sour and rot. Overnight is usually good. Many sources recommend 8-12 hours and no more than 24 hours. Again, too much soaking and the seeds will start to decompose.
The answer is, no, you don't technically need to soak the seeds before sowing, but it sure does speed up germination big time. We are all aware that seeds in the wild can germinate without our assistance.
Seeds absorb water when soaked. This makes them soft and big. Soaked seeds germinate faster. It is also easy to cook them.
Vinegar is an aqueous solution of acetic acid, which inhibits the process of seed germination. Higher concentration of acetic acid may destroy the seed vigor and inhibit the germination of seeds. Overall, vinegar can kill the seeds, the leaf, and possibly the entire plant.
Soaking is beneficial in two ways; it can soften a hard seed coat and also leach out any chemical inhibitors in the seed which may prevent germination. Anything from 1-3 hours in water which starts off hand hot is usually sufficient. If soaking for longer the water should be changed daily.
Like most things in gardening, there are always exceptions to this rule of 2-3 seeds per hole. If you're planting large seeds like cucumbers, melons, or pumpkins, you should only use one seed per hole. However, you can still plant seeds close together and then thin them out once they've established themselves.
Dry seeds are known as dormant seeds. They remain alive without germinating for months or years. When the seed is soaked in water, enzymes get activated by absorbing water, and thus, it helps in germination and development of embryo.
Hot water seed treatment has the beneficial effect of priming seeds, resulting in faster germination than untreated seed. However, the treatment can decrease germination rates, especially of older seed (more than 1 year old) or seeds that were grown under stressful environmental conditions.
Seeds may float because they lack viable embryos or nutrient stores, making them less dense than “good” seeds that sink in water. Or, they may float because they have air pockets inside, which don't always affect seed vigor or viability.
Because they absorb moisture more easily, they also need to be dried at a higher temperature to make sure they completely dry out. When soaking nuts, add 1-2 tablespoons of coarse salt to the filtered water. Before drying the nuts be sure to rinse them to remove the salt residue.
Hot water shortens the soaking time, but bear in mind that heat destroys the nutrients. Ideally, make sure the water temperature is not over 50-60 C. If you use room temperature water soak the nuts in a bowl with enough water to cover them well because the walnuts will expand a bit during the soaking.
Soaking isn't always necessary, and shouldn't be a knee-jerk reaction. Bear in mind that many modern seeds have been bred for reliable germination, in contrast to wild varieties, and so soaking may do little to improve things. However, some seeds can certainly benefit from a soak.