With their six petals that range in color from yellow, white and pink to blue, red and purple, irises (Iris spp.) are some of the most popular gardening plants. Consisting of more than 200 species, many irises are hardy to U.S. Department of Agriculture plant hardiness zone 3. Siberian iris (Iris sibirica) and crested iris (Iris cristata), for instance, can thrive in USDA plant hardiness zones 3 through 9. Although irises can be propagated by vegetative means, you can also start them from seeds, although cultivars won’t come true unless they’re a pure strain.
Things You’ll Need
Seed-starting tray or pot
Pick the seedpods as soon as they turn brown and crack open at the top. Do this toward the end of summer when the plants are done blooming and the flowers have faded. If pollinated, expect to find about 60 glossy brown seeds per pod.
Fill a small bowl with enough water to cover the seeds. Soak the seeds in the bowl of water for two weeks. Every day, drain the liquid, pouring it in a strainer so you catch the seeds. Refill the bowl with fresh water and place the seeds back in it. This soaking process will eliminate the germination inhibiting properties of the seeds.
Fill a seed-starting tray or a pot up to 1 inch from the top with moist seed-starting mix. Sow the seeds 1/2 inch deep in the container, spacing them at least a 1/2 inch apart. Use a pot with drainage holes to avoid standing water.
Place the container outside in a shady area to expose the seeds to the natural cold weather and temperatures between 33 and 38 degrees Fahrenheit. Do this in the fall or early in the winter so the seeds are exposed to the cold for at least 90 days. During this time, water the soil regularly to keep it moist, not wet. Expect the seeds to germinate when the weather warms up in spring.
Transplant the seedlings when they’re about 5 inches tall in a sunny to partial shady area of the garden that has well-drained soil that’s enriched with a 2-inch layer of compost. Carefully spoon them out of the growing container and plant them about 12 inches apart.
Instead of direct sowing the seeds in the garden, always sow them in a container so the rain can’t wash them away.
Instead of sowing the seeds in a container before exposing them to cold temperatures, you can also stratify them in a plastic sandwich bag that’s filled with an equal amount of moist peat moss. Place the bag in the refrigerator — not the freezer — to mimic the cold outdoor climate. Mist the medium regularly with a water-filled spray bottle to keep it moist. After three weeks, sow the seeds outdoors in spring.
Iowa State University Extension and Outreach: Irises for the Home Landscape
Louisiana Iris Farms: Louisiana Native Iris
Fine Gardening: Try Your Hand at Hybridizing with Irises
Tucson Area Iris Society: How To Grow Iris From Seeds
Restoring the Tallgrass Prairie; Shirley Shirley
Taylor’s Guide to Growing North America’s Favorite Plants; Barbara Ellis