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Why do many temperate conifer seeds need a cold and moist period before germinating?

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The massive Grizzly Giant sequoia tree stands with a wide, reddish-brown trunk and a hollowed base, surrounded by other tall trees in Mariposa Grove, Yosemite National Park. — Conifer A giant sequoia (*Sequoiadendron giganteum*) estimated to be between 1,900 and 2,400 years old, Grizzly Giant is the oldest tree in the Mariposa Grove, Yosemite National Park, California.

Many temperate conifer seeds require a period of cold and moist conditions—a process known as stratification—to overcome dormancy.12

Even when environmental conditions appear favorable for growth, the embryos within these seeds remain dormant. They must undergo a series of physiological changes called afterripening before they are capable of germinating. For many cool temperate species, this internal development is triggered by exposure to cold and moisture, which effectively signals that the winter season has passed and conditions are becoming suitable for seedling survival.12

This requirement serves as an ecological safeguard, preventing seeds from germinating prematurely during a brief warm spell in autumn or winter, which would likely result in the death of the young seedling. By ensuring that germination occurs only after a sustained cold period, the plant increases the likelihood that the seedling will emerge during the more favorable conditions of spring.12