Easy Grow
Moist Stratification
Many of the prairie flowers and most woodland wildflowers require moist stratification to break dormancy and yield high rates of germination. For example, Shootingstar (Dodecatheon meadia) has a zero rate of germination when dry stratified, but after 30 days of moist stratification it will germinate close to a 100 percent rate. Different species require varying lengths of moist stratification to break dormancy. Lupine (Lupinus perennis) requires only 10 days. After two weeks of treatment, it will often begin to germinate while still in the refrigerator. Members of the genus Iris require 90 days of moist stratification to yield good germination. Dormancy in most species can be broken with 30 days with this treatment. Seed can be moist stratified by mixing it with an equal or greater volume of slightly damp, inert material. We have found that oak or pine sawdust works admirably for this purpose. It is easy to work with, absorbs moisture and transfers it to the seed well, and the relatively high acidity of the sawdust limits the growth of bacteria during the stratification process. Vermiculite, perlite, and peat moss can also be used as the inert material. The inert matter should be only lightly dampened prior to mixing with the seed. If water can be wrung out of the sawdust or peat moss by squeezing it, then it is too wet. Vermiculite and perlite should be moistened in a bowl or colander, so that excess water will drain off. Mix the seed and inert matter together thoroughly, place in a zip-top plastic bag, labeled with the species and date, and place it in the refrigerator for the specified amount of time for the species being treated. Another method of moist stratifying seed is to plant the seed directly into flats, cover them with plastic wrap to retain moisture in the soil, and store them in a refrigerator or walk-in cooler. If such facilities are not available, the flats can be seeded in fall, and stored over winter in an unheated building or greenhouse. Make sure that the flats are protected from damage by mice and other animals during winter storage.
Timing of Moist Stratification Pretreatment
The initiation of moist stratification should be timed so that the seed will be removed from the refrigerator at the appropriate time of year for optimal germination. Cool-season plants should be started in mid-March to early April when temperatures are still cool. Warm-season plants can be started once the air temperature reaches the high 70s or low 80s F.
Many of the prairie flowers and most woodland wildflowers require moist stratification to break dormancy and yield high rates of germination. For example, Shootingstar (Dodecatheon meadia) has a zero rate of germination when dry stratified, but after 30 days of moist stratification it will germinate close to a 100 percent rate. Different species require varying lengths of moist stratification to break dormancy. Lupine (Lupinus perennis) requires only 10 days. After two weeks of treatment, it will often begin to germinate while still in the refrigerator. Members of the genus Iris require 90 days of moist stratification to yield good germination. Dormancy in most species can be broken with 30 days with this treatment. Seed can be moist stratified by mixing it with an equal or greater volume of slightly damp, inert material. We have found that oak or pine sawdust works admirably for this purpose. It is easy to work with, absorbs moisture and transfers it to the seed well, and the relatively high acidity of the sawdust limits the growth of bacteria during the stratification process. Vermiculite, perlite, and peat moss can also be used as the inert material. The inert matter should be only lightly dampened prior to mixing with the seed. If water can be wrung out of the sawdust or peat moss by squeezing it, then it is too wet. Vermiculite and perlite should be moistened in a bowl or colander, so that excess water will drain off. Mix the seed and inert matter together thoroughly, place in a zip-top plastic bag, labeled with the species and date, and place it in the refrigerator for the specified amount of time for the species being treated. Another method of moist stratifying seed is to plant the seed directly into flats, cover them with plastic wrap to retain moisture in the soil, and store them in a refrigerator or walk-in cooler. If such facilities are not available, the flats can be seeded in fall, and stored over winter in an unheated building or greenhouse. Make sure that the flats are protected from damage by mice and other animals during winter storage.
Timing of Moist Stratification Pretreatment
The initiation of moist stratification should be timed so that the seed will be removed from the refrigerator at the appropriate time of year for optimal germination. Cool-season plants should be started in mid-March to early April when temperatures are still cool. Warm-season plants can be started once the air temperature reaches the high 70s or low 80s F.