The practice known as stratification by gardeners is simply mixing thoroughly the seeds with sand in a box and burying outside on dry ground, with the top about four inches under the earth, where it will freeze solidly if at the north, or be kept moist if at the south. It is practised with hard, bony seeds that are injured or ruined by drying, such as pits of plum, cherry, honey locust, Kentucky coffee-tree, some of the shrubs, and seeds of the small fruits and roses. If well mixed when stratified, it is usual to sow the seed and sand together in the spring.
Such nuts as the hazel, filbert, chestnut, acorns, and hickory nuts, it is best to mix with sand and store in a cool cellar, protected by covering from rats and mice. But kept in this way the nuts will usually sprout early in the spring. For this reason we have practised planting when the ground has thawed out three inches deep in the spring. Such nuts ńs the black walnut, English walnut, and butternut are provided by Nature with a covering that holds moisture as it decays. It is best to cover these, as spread out in thin layers in a grove, with forest leaves for early spring planting. Seeds that require to be kept moist should be stratified very soon after gathering, and the pits of the stone fruits should be washed to free them from all traces of pulp, followed by partial drying before mixing with the sand. If not washed and partly or wholly dried, the adhering pulp often develops fungus growth that is destructive. If the stone fruits rot in boxes or piles and the pits are washed out and dried, they rarely can be made to germinate on account of fungus injury.