The red alder, Alnus rubra, is a member of the birch family. It grows along the northern Pacific coast of southern California and goes all the way up to southeastern Alaska. You will rarely find the red alder growing east of the Cascade Range in Oregon and Washington, or the Sierra Nevada.
Red Alder is a fast growing tree. In the first five years, it can grow 30 feet. The root system is extensive and a deep hole is needed to contain them. The wood of red alder is used in the making of wood products, such as furniture, cabinets, plywood, and writing paper.
You can propagate the red alder in two ways: mound layering or sowing the small winged seeds. The seeds are sold online, but if there is a tree nearby, you can collect the seeds for free. The seeds disperse at varying times depending on where the red alder trees are growing. In Alaska, collect the seeds in September. The further south the trees grow, the later in the season, it goes for collecting the seeds. For those living in the California, collect the seeds until December.
Mound Layering
When the stems of young alder plants are a few months old, cut them down to the ground. Although this sounds severe, it is necessary step to starting red alder trees. Cover the stump and the base of the sprouts with soil.
Moisten the area with water, but do not add so much that the soil is soggy. Continue to keep the area moist until the end of the growing season.
Carefully remove some of the soil and check for roots. When the roots have formed, it is time to sever the sprouts from the stump. Plant the rooted sections in the area of your choice.
Sowing Seeds
Fill several cell packs or a seed tray with potting soil. If you use cell packs, fill as many as you have seeds to fill. With your fingers or a special tamper, firm the soil in place so the seeds won’t sink into the soil when watered.
Water the potting soil thoroughly allowing the excess water to drain from the drainage holes.
Sow one seed per cell, or scatter them thinly over the soil in the seed tray. Do not cover the seeds. They require sunlight to germinate.
Place the seeding tray in a bright, sunny location. Check the soil daily. Mist the surface of the potting soil to keep the soil evenly moist. Continue to grow the alder trees until they are 3 inches tall. Then fill enough 6-inch pots with potting soil and transplant the seedlings, one per pot.
Place the pots in a bright location Grow the small red alder trees in the pots for a period of one year, before transplanting into its permanent place.
Sources:
Oregon State University: Red Alder (Alnus rubra)
“American Horticultural Society A to Z Encyclopedia of Garden Plants”; Christopher Brickell; 2004
British Columbia Government: Red Alder
