Iris can be very rewarding grown from seed. The diversity of seedlings from a cross or even collected from wild species can be quite remarkable. It must be remembered that seed from a certain cultivar does not always reproduce that cultivar. If the cultivar is a seed strain than any progeny that fit the discription of the strain can be called by that name. But the usual case is that cultivars are clones and can only be propagated asexually. But there is the chance that a seedling may be even better than its parent and that it deserves a cultivar name.
Patience is perhaps the most important part of seed raising. Seeds of many species may germinate immediately if removed from the pod just as the pod splits to open and quickly planted. But most often seed is stored and later sown. These dryer seeds may require a period of stratification. Stratifying usually is just leaving the flat outside through the winter exposed to rain and freezing and thawing. Some people have had good results placing the seeds in the refrigerator with a moist paper towel in a sealed plastic bag for about 6 weeks. Whatever the cold treatment often some or all the seeds may not germination until the following year and a second winter. Or sometimes they may germinate in the fall when the rainy cool weather returns. Unless the species is a tropical variety there is probably no reason to worry about the tiny seedling experiencing a cold winter. Dykes reported that some aril seeds took as long as 16 years to germinate. For most Irises, seeds will germinate the first spring, but if they do not, do not through the flat away because they may sprout that fall or the following spring.
A rule of thumb for how deep to place is a depth twice the diameter of the seed. But seeds will often germinate right on the soil surface if the do not dry out badly. Also seeds may emerge from an inch or two below the surface, a situation I have had when I reused the potting soil for a pot plant and was later surprised with seedlings.
Please add your experiences with various types of Iris seeds.
-- Main.RPries - 2009-11-03