The Dawn Redwood (Metasequoia glyptostroboides) is a fascinating tree, often called a “living fossil” because it was known only through fossil records until its rediscovery in the 1940s. As a deciduous conifer, it features feathery, bright-green foliage and stunning russet fall color before dropping its needles. This tree is also known for its rapid growth rate, capable of adding three to five feet in height per year under ideal conditions. Successfully growing this ancient giant from its tiny seeds can be a rewarding project, but it requires careful attention to specific pre-treatment and environmental steps.
Preparing the Seeds for Treatment
Germination begins by obtaining and preparing the seeds, typically collected from cones or purchased from a reputable source. Dawn Redwood seeds naturally have a high proportion of infertile or “hollow” seeds, meaning a large number of seeds must be planted to ensure a successful yield. To prepare the seeds for treatment, place them in a container of clean, room-temperature water for a soak lasting 24 hours. This initial 24-hour soaking softens the seed coat (a mild form of scarification) and helps identify non-viable seeds, which will float. After 24 hours, gently strain the seeds and discard the water. They are now ready for cold treatment.
The Cold Stratification Process
Dawn Redwood seeds possess a natural dormancy mechanism that must be broken by mimicking the cool, moist conditions of winter, a process known as cold stratification. To begin, select a small, sealable container or a plastic zip-top bag and a damp, sterile medium, such as peat moss, vermiculite, or a moistened paper towel. The medium should be damp, not saturated, as excessive moisture can lead to fungal growth. Mix the seeds into the medium, ensuring they are well-distributed, and then place the sealed container into a household refrigerator.
Maintain the refrigerator temperature consistently between 34 and 40°F (1 to 4°C). This moist chilling period should last between 60 and 90 days, though up to 120 days is sometimes recommended for maximum effect. Check the seeds weekly for mold or drying out, aerating the bag briefly and adding water if the medium dries. If any seeds begin to sprout prematurely inside the refrigerator, they should be immediately removed and planted in soil.
Sowing the Seeds and Initial Setup
Once stratification is complete, move the seeds into a sterile, well-draining seed-starting mix. A blend of 60% potting mix with 20% perlite and 20% sand or sphagnum moss provides excellent aeration and moisture control. Fill a seed tray or small pot with the mix, moisten it thoroughly, and then sow the tiny seeds very shallowly on the surface. Dawn Redwood seeds require light to trigger germination, so they should be barely covered with a thin dusting of mix, no more than 1/8 inch deep.
To create the ideal microclimate, cover the container with a clear plastic dome or wrap to maintain high humidity (70 to 80%). Place the setup in bright, indirect light, such as under a grow light or near a bright window, avoiding direct sunlight which can overheat the container. Maintain a consistent warm temperature for germination, ideally between 70 and 75°F (21–24°C). With these conditions, the seeds should begin to germinate within two to four weeks after removing them from the cold.
Caring for Seedlings and Transplanting
As seedlings emerge, adjust the environment to prevent fungal issues like damping-off, which is common in high-humidity. Once a significant number of sprouts have appeared, gradually increase the ventilation by propping the humidity dome open or puncturing the plastic wrap. After about a week, the cover should be removed completely to allow for proper air circulation and to prevent the seedlings from becoming soft or “leggy.” Ensure the young plants receive plenty of bright light to promote strong, stocky growth, and keep the soil consistently moist but never waterlogged.
When seedlings develop their first two to three sets of true leaves and reach a few inches in height, they are ready for transplanting into individual pots. Move each seedling carefully into a larger container, such as a one-gallon pot, filled with a well-draining soil mix rich in organic matter. Before planting them outdoors, the young saplings must be “hardened off” by slowly exposing them to increasing periods of direct sunlight and outdoor temperatures over a two-week period. This gradual acclimation strengthens them for a successful transition to their permanent location in the landscape.