seeds
Stratification
Last reviewed 2026-10-04
Stratification is a period of controlled temperature and moisture that helps a dormant seed become capable of germinating. Many temperate plants need a stretch of cool, moist conditions that imitates winter. Others need warm stratification, or a sequence of warm and cool periods. The required treatment is specific to the species.
What it means
Some seeds are viable but physiologically dormant. Their embryos need a seasonal signal before growth begins. Cold, moist stratification commonly means placing seeds in a damp medium at a refrigerator temperature for a stated number of weeks. The seed packet or propagation reference should set the duration and temperature.
How it affects the garden
Keep treated seed labeled and separate from food. The medium should be moist, not dripping wet, and the container should be checked for mold or early roots. Once the treatment is complete, sow promptly and provide the germination conditions the species needs. Outdoor sowing can provide natural stratification, but it is less predictable because winter temperature and moisture vary.
Stratification matters most for many native perennials, trees, and shrubs. It is not a universal pre-sowing step for vegetables. If a seed packet does not call for it, adding a refrigerator treatment can delay or harm the sowing.
Example
A packet of a native perennial may specify 30 days of cold, moist stratification. The gardener mixes the seeds with a barely damp medium, refrigerates the labeled container for that period, then sows the seeds in a tray.
Common confusion
Stratification is not scarification. Scarification weakens a physical seed coat. Stratification changes the seed's physiological state through temperature and moisture.
Sources
The Lady Bird Johnson Wildflower Center seed propagation guide explains why native seeds can require dormancy treatments.
