I find it easier to remove a thick straw cover than mess with gravel. It keeps the rain from "floating" seed, too. I can lift the straw with the chicken wire and put it back if a sudden freeze shows up as in 2007.
<<top with 1/2" pea gravel. The top gravel prevents frost heaving. >>
It's easy to let mother nature take care of the germination here in KY, where the winters are typically over three months long. Even our most mild winters are sufficient for decent germination. In 25 years, I've never experienced really bad germination across the board--only in some crosses. There are times when I get low to no germination on some pink & orange crosses. Aggravating. Makes me wonder if they sprout early and get zapped with the late (er) frosts. I've considered bringing these inside starting in early March. Just in case.
At any rate, any new hybridizer on the list is getting a wide range of things to try. Comparison/talk is good!
From: Vicki <email@example.com>
To: iris-photos <firstname.lastname@example.org>
Sent: Fri, Dec 3, 2010 4:48 pm
Subject: [iris-photos] re: seeds
I have been lurking and reading about all the work you are doing to grow iris. We have lived in a variety of areas from high mountain deserts to lowlands where winters were as cold as 25 below to 29 above.We never have bothered with soaking or refrigerating seeds. No matter where we lived we germinated our seed simply by letting the seed shrivel and shrink until about November/December. We then plant the dry seed in potting soil in pots. Placing a little gravel in the bottom to assist drainage, add the moist soil, push the seed in slightly and top with 1/2" pea gravel. The top gravel prevents frost heaving. The pots are then set out on plastic or sometimes a raised area and turned over to mother nature. In very dry areas one must add some water occasionally. Klamath Falls has about 8 months of winter weather and can have a freeze any month. Yet we successfully germinated 1300 seeds one winter.
Hope this may help. And yes, we have very good germination.
Maybe Mother Nature knows best? You might give it a try.