Douglas Iris (Iris douglasiana) is a perennial herb, native to the coastal regions of California and southern Oregon. This species blooms from May to June, displaying colors from pale cream and light lavender to deep reddish-purple. Growing Douglas Iris from seed offers a rewarding experience, providing a cost-effective way to cultivate this beautiful plant and even explore new color variations that arise from natural hybridization.
Collecting Douglas Iris Seeds
Collecting Douglas Iris seeds begins after the flowering period, typically between June and August, once the seed pods mature. These pods are large capsules that transition from green to dark brown and begin to open at the top when ripe. Monitor them closely; they can rapidly disperse their seeds within a couple of days after ripening.
To collect seeds, carefully snip the mature, dry, brown pods from the plant to prevent spilling. Each capsule can hold between 20 to 80 seeds. After collection, store the seeds in paper envelopes at room temperature until they are ready for planting. Stored properly, Douglas Iris seeds can remain viable for up to 10 years.
Preparing Douglas Iris Seeds for Germination
Douglas Iris seeds require pre-treatment to encourage successful germination, involving scarification and stratification. These processes help overcome the seed’s natural dormancy, due to a hard seed coat and chemical inhibitors. Scarification involves weakening the seed coat for moisture penetration.
For scarification, gently nick the seed coat with a sharp knife or use sandpaper to abrade the surface. After scarification, seeds benefit from cold stratification, which mimics the natural winter conditions they would experience outdoors. Place seeds in a moist medium, such as sand or vermiculite, in a sealed bag and refrigerate them for 6 to 8 weeks. Some sources suggest a stratification period of one month.
Alternatively, sow the seeds outdoors in pots during autumn or early winter, allowing nature to provide cold stratification. Ensure the medium remains consistently moist but not waterlogged throughout this period. Germination typically occurs in the spring, around the time other irises begin to bloom, though some seeds may take longer to sprout.
Planting Douglas Iris Seeds
Once Douglas Iris seeds are ready for planting after stratification. The best time to plant, particularly after indoor stratification, is in late winter or early spring, after the last expected frost. If stratifying outdoors, seeds sown in autumn will germinate in spring.
Douglas Iris prefers well-draining soil with organic matter, with a slightly acidic to neutral pH range of 5.5 to 7.0. A suitable soil mix includes sand, loam, and compost or peat moss. When planting, sow the seeds about 1/8 to 1/2 inch deep. If planting in containers, use pots at least 6 inches deep to accommodate root development.
Gently cover seeds with soil and water thoroughly to settle the medium. If starting seeds indoors, provide early morning sunlight and bright, indirect light, or use grow lights for four to six hours daily.
Caring for Douglas Iris Seedlings
Young Douglas Iris seedlings need consistent moisture, light, and eventual transplanting. Seedlings require consistent soil moisture; avoid letting them dry out completely. Do not overwater; Douglas Iris does not tolerate waterlogged conditions.
As seedlings grow, they need bright, indirect light. Gradually acclimate them to outdoor conditions, a process known as hardening off, by exposing them to increasing periods of outdoor light and temperature over about a week. This prepares them for transplanting. Douglas Iris prefers partial shade in warmer climates but can tolerate more sun in mild, coastal areas.
When seedlings are 3 to 6 inches tall, usually in May, they can be transplanted to their permanent garden spot. Space them about 1 to 2 feet apart. Douglas Iris can be slow to establish in its first year, and it may take two years before plants begin to bloom.