Seed, the gardener's world has gone to seed. Berries, floating puff balls, the dispersal is upon us. As these varied embryos fall or fly, they are prepared to wait for the perfect set of circumstances to occur before they risk the one chance they have to sprout. So many days of cold, cycles of freezing and thawing, even the correct shade of light; bright, totally dark, or somewhere in between say grow.
Trees and shrubs are often sealed with a hard coat. The shell that protects the interior, hard as a rock (literally), it may take two years, a passing of two winters before the seed walls are weakened enough. Think of that and then understand that water lotus seeds have sprouted after waiting two thousand years!
Annual plants, those that live a growing season and then die have simpler seed, naked in comparison. Produced in such abundance, literally falling in heaps, if one emerges too early, there are hundreds, thousands to take their place. These are the first to arrive in open spaces, the first in succession. A trigger is often sunlight, a bright level of light says grow, grow while nothing else resides here. And they do, out pacing others as they rush to fill the vacancy. Exuberant in their pursuit of life, optimistic and carefree.
Most gardeners grow some plants from seed. Well, we all grow plants from seed by simply gardening, but I mean intentionally. Do you have a seed collection? Envelopes, partly used seed packets, or the random plastic prescription bottle devoted to zinnia seeds? Some of these seeds are viable for a very long time (as pointed out), others may weaken or lose their ability to sprout. Storing seeds in a cool, dark place is helpful, also using paper envelopes or glassine envelopes to maintain even temperatures.
You can always check the viability of your annual seed by rolling some up in a moist paper towel and placing them in a sealed bag (like a ziplock bag). Moisten the towel, squeeze so it's not dripping wet, line your seed along the top, do about ten, roll it up and slide into your bag. Check every other day or so, some may sprout in a day, others three to ten days. This test for viability will determine the percentage of seeds that are good and you can sow accordingly. Much better than the pot, soil, and wait method.
With hardy seeds, perennial or woody, I prefer to sow in fall, now to be exact. Freeze cycles send clear messages and seed coats weaken. In separate pots I will line them up outside. Maybe cover them in chicken wire to keep out hungry squirrels. A general rule for planting is three times a seed's size deep. Small seeds can be surface sown (like draba), something as large as an acorn would be two to three inches deep. Letting the natural cycles of winter take their course helps mightily.
Hard seed can be fooled into sprouting by nicking the hard shell. A rub between sand paper or a nick with nail clippers lets water permeate the outer shell. This technique may work if you are intent on indoor sowing. Nursery operators have many methods to coax a seed to sprout, everything from gibbrellic acid baths to cold stratification, which mimics the outdoors but speeds up the process.
Now is seed collecting time. If you wait, berries may be gone, annual seed will have fallen, and many others will have been blown away. Find them before you can't. For outdoor sowing of hardy plants, finish by mid-December. Too long in warm storage will certainly hamper their ability to sprout, confusion for the seed and exasperation for the gardener.