Advanced Seed Starting
Most plants have adapted to the weather conditions under which they grow in their native habitat. Some, especially perennials, shrubs and trees that grow in colder climates, need to go through a frigid period before they can germinate. Stratification is the process of simulating cold weather conditions to encourage germination. Pansies and violas fall into this category. Stratification temperatures should be around 40 degrees, making your refrigerator the perfect host for stratified seeds.
Some reference books tell you to put the seeds between moist paper towels, and though this will certainly work, I don't advise it. If you don't put the towels in a zippered plastic bag they'll dry out. If you do, the seeds are apt to rot. I prefer sowing the seeds in the flat I plan on growing the seedlings in, watering lightly, and popping the flats into a gallon-sized zippered plastic bag.
Mark a calendar so you know when to take the seeds out of the fridge. Once they have served their stratification time, move the flats to a warm location, still inside the plastic bag. Be patient. Some perennials and most all trees and shrubs have a very long germination period. If the seed packet doesn't give you this information, check a reference guide. Remove the flat from the plastic bag when the seeds begin to sprout.
Stratification times vary from a few days to several months. The following list contains stratification times for a few of the more commonly grown from seed plants. Cleome: 3-5 days Pansy or viola: 1 week Columbine: 3 weeks Allium (from seed): 4 weeks Echinacea: 4 weeks
Double dormancy is a complicated process that you won't encounter unless you plan on trying to start a tree or shrub from seed. In nature these seeds go through a couple of seasons before they germinate. To simulate this, the seed is planted and then kept at temps of 65-85 degrees for four to six months prior to stratification. Maples, cotoneaster and yews all need double dormancy. See Halpin's book for more detail.
Some seeds have hard coats that need soaking before the seed will germinate. This copies the soggy soil conditions of spring. Put the seeds in a bowl that will hold 5-6 times the volume of the seeds. Fill the bowl with very hot water, and let stand overnight. Drain and plant the seeds as soon as your remove them from the water. Some seeds that need soaking are sweet and
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