Cherry trees (Prunus spp.) grow in cold climates where the ground goes through a period at or near freezing temperatures for several months each winter. A seed dropped to the ground in late fall in a cold climate perishes if it germinates and begins growth before winter sets in. As a cold-climate tree, cherry tree seeds evolved to require a period of chilling to prevent early germination. The seeds don't need to actually freeze, but must be kept for an extended period at temperatures below 40 degrees Fahrenheit.
Cherry seeds require a period of cold exposure, called stratification, before they will germinate.
Two Reasons to Plant Seeds
Cherry trees do not reproduce true to seed. Commercial growers and home gardeners plant grafted cherry trees. There are two reasons to grow cherry trees from seed: It's a fun project and a good way to get a young child involved with the growing process, and commercial growers use cherry trees planted from seed to provide the rootstock for grafting. Cherry seeds fresh from the market require a period of cold temperatures to break seed dormancy.
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Preparing Cherry Seeds for Stratification
"Stratification" describes a process used to break seed dormancy. Stratification requirements vary depending on the type of seed and the environment to which it has adapted. Some seeds need to be damaged, burned, digested or crushed before they come out of dormancy, a process called scarification. Others simply need to spend a few months dormant before germination, without scarification or stratification treatment. And some seeds may be sown immediately after they're harvested for quick germination. Cherry trees require cold stratification to emulate the conditions the seed experiences on the ground under winter snow.
Harvest ripe cherries from a tree or purchase ripe cherries at the market. Seeds from fruits that ripen on the tree germinate more reliably than from fruits that were picked early. When cherries are picked early, the seeds do not always fully develop. Clean off all traces of fruit and fruit pulp, and thoroughly rinse the seeds in a colander. There's no need to dry the seeds out before stratification, because you are going to place them in a damp medium.
Stratification for Cherry Seeds
Spread a 1- to 2-inch-thick layer of slightly damp peat moss or damp sand over the bottom of a bucket, or lay a 1-gallon-size zip-top bag on its side and spread a 1-inch layer of damp peat moss over the bottom. Place clean cherry seeds on the medium, about 1 inch apart. Cover the seeds with a second layer of the damp stratification medium. When using a bucket or container, stratify multiple layers of cherry seeds separated by 1 inch of damp medium.
Place the bucket, container or zip-top bag in a cold-storage area. The refrigerator crisper drawer works well for small containers and zip-top bags. Keep the cherry seeds between 33 and 41 F. The seeds require between 98 and 105 days of cold storage to break dormancy. Check the stratification medium periodically to make sure it remains damp. The medium should stay damp in a closed container, but if it does start to dry out, mist with water to dampen the environment around the seeds.