You will find organic garden seeds available this spring at a higher price. Are organic seeds better than regular seeds? My answer is no. The plants producing the seed, say lettuce, use nitrogen after the soil microorganisms break the chemical or organic fertilizers down to nitrate or ammonium which is taken up to the roots. As long as they get this nitrate or ammonium, they are happy. An organic seed will not grow better than a regular one.
Organic seed means the plant producing the seeds was grown organically with organic fertilizer and chemicals. If the grower uses chemical insecticide, does any of the residue go and stay in the dormant seed? No, it is diffused into the plant to gradually breakdown. So, whether a seed is grown organically or with chemicals, it has no meaning to the seed itself.
Heirloom seeds are referred to older varieties that are field pollinated. They are available as regular seeds and organic seeds. I am not saying that organic raising of eatable plants is bad. Anytime you put manure or other organic material in the soil, you increase the soil’s health.
As for chemical vs organic pesticides, some organic insecticides can be more dangerous than chemicals. Chemical insecticides have a tendency to break down rather quickly.
Now treated seed is different. This seed is treated with a fungicide to prevent rotting in cool, wet soil. This seed is safe if you wash your hands after planting. Seed treated with an insecticide is not available to gardeners.
As for GMO seeds (gene-modified seeds), they are not available as garden seeds.