Many plants, such as wildflowers, native species, and perennials, produce seeds that will not sprout right away.
Seed stratification is a technique gardeners use to simulate natural winter conditions so certain seeds will germinate. For gardeners in our climate, winter sowing and fall planting often work beautifully because the natural winter provides the exact conditions many seeds need.
In nature, those seeds fall to the ground in Autumn, experience cold, moist winter conditions, and then germinate when spring arrives. Stratification recreates this process by manually exposing seeds to cool, moist conditions for a set period of time, which breaks their dormancy.
Gardeners usually stratify seeds by placing them in a moist medium such as sand, peat, or paper towels, sealing them in a bag or container, and storing them in the refrigerator for several weeks to a few months depending on the species.
Once the required chilling period is complete, the seeds are planted and often germinate more reliably. This simple step can greatly improve success when growing plants such as many wildflowers, trees, and shrubs.
How to know which seeds to stratify, and for how long
The length of time varies by species, but most require 30–90 days in the refrigerator at about 34-40°F.
Here are 10 seeds that benefit from cold stratification and grow especially well in Colorado gardens, particularly in sunny, dry, or high-altitude conditions. Many are native or well-adapted to our climate, so they are reliable choices.
In nature, those seeds fall to the ground in Autumn, experience cold, moist winter conditions, and then germinate when spring arrives. Stratification recreates this process by manually exposing seeds to cool, moist conditions for a set period of time, which breaks their dormancy.
Gardeners usually stratify seeds by placing them in a moist medium such as sand, peat, or paper towels, sealing them in a bag or container, and storing them in the refrigerator for several weeks to a few months depending on the species.
Once the required chilling period is complete, the seeds are planted and often germinate more reliably. This simple step can greatly improve success when growing plants such as many wildflowers, trees, and shrubs.
How to know which seeds to stratify, and for how long
The length of time varies by species, but most require 30–90 days in the refrigerator at about 34-40°F.
Here are 10 seeds that benefit from cold stratification and grow especially well in Colorado gardens, particularly in sunny, dry, or high-altitude conditions. Many are native or well-adapted to our climate, so they are reliable choices.
Three simple seed stratification methods to try
1. Refrigerator Method (Most Controlled)This is the most common and reliable method. Place seeds in a moist medium such as damp sand, peat moss, vermiculite, or a slightly damp paper towel. Seal them in a labeled plastic bag or container and store them in the refrigerator (34-40°F) for the recommended time, usually 30-90 days. Check occasionally to ensure the medium stays lightly moist but not soggy. After the chilling period, plant the seeds in pots or directly in the garden.
2. Winter Sowing Outdoors (Easiest Method)This method lets nature do the work. Sow seeds in containers (such as milk jugs with drainage holes) filled with potting soil, water lightly, and place them outside in late fall or winter. The seeds experience natural freezing and thawing cycles and germinate in spring when conditions are right. This technique works especially well for wildflowers, perennials, and native plants. See our recent article on winter sowing.
3. Direct Fall Planting Many seeds can simply be planted directly in the garden in late Fall. Scatter or plant them at the recommended depth, then allow winter weather (snow, moisture, and cold) to naturally stratify them. When spring arrives, the seeds awaken and sprout as temperatures warm.
1. Refrigerator Method (Most Controlled)This is the most common and reliable method. Place seeds in a moist medium such as damp sand, peat moss, vermiculite, or a slightly damp paper towel. Seal them in a labeled plastic bag or container and store them in the refrigerator (34-40°F) for the recommended time, usually 30-90 days. Check occasionally to ensure the medium stays lightly moist but not soggy. After the chilling period, plant the seeds in pots or directly in the garden.
2. Winter Sowing Outdoors (Easiest Method)This method lets nature do the work. Sow seeds in containers (such as milk jugs with drainage holes) filled with potting soil, water lightly, and place them outside in late fall or winter. The seeds experience natural freezing and thawing cycles and germinate in spring when conditions are right. This technique works especially well for wildflowers, perennials, and native plants. See our recent article on winter sowing.
3. Direct Fall Planting Many seeds can simply be planted directly in the garden in late Fall. Scatter or plant them at the recommended depth, then allow winter weather (snow, moisture, and cold) to naturally stratify them. When spring arrives, the seeds awaken and sprout as temperatures warm.