Caren White is a Master Gardener and instructor at Home Gardeners School. She has been associated with Rutgers Gardens for over a decade.
Love iris but your yard is too wet? Forget the bearded iris. You need Siberian iris (Iris sibirica). It prefers moister soil than the drought-loving bearded irises. You can even plant it along the sides of streams or as part of a rain garden.
What is Siberian Iris?
Contrary to their name, Siberian iris are not originally from Siberia which is too cold for them to grow. Their native habitat stretches from northern Italy east to Turkey and the Caucasus. They have been in cultivation in Europe since the Middle Ages. The Europeans that colonized North America, brought Siberian iris with them. It escaped their gardens and has naturalized in Canada and the Eastern United States.
Siberian iris are known as beardless iris. Their flowers are smaller than bearded iris and lack the fuzzy “beard” of their taller cousins. Their leaves are slender and more grass-like. They bloom towards the end of the “iris season” in late May and early June. The flowers come in all the same colors as bearded iris, although most Siberian iris cultivars are blue or purple. They range in height from 12” to 40”.
How to Grow Siberian Iris
Siberian iris prefers full sun but will tolerate partial shade as long as they get a few hours of full sun each day. They like moist, well-drained soil that is more on the acidic side. The rhizomes have a tendency to dry out when they are out of the ground, so soaking them overnight before planting is a good idea. Plant them 18 to 24 inches apart with the tops of the rhizomes at least one inch below the soil surface. Keep your plants well-mulched to make sure that the soil remains cool and moist. You can fertilize them with a balanced fertilizer such as 10-10-10 twice each season, once in the spring before they bloom and then again about a month after they bloom to help them replenish their rhizomes for next year.
There is no need to deadhead your Siberian iris after they bloom but you might want to do so to prevent them from going to seed. Siberian iris can be grown from seed. If you allow their flowers to mature into seeds, they will reseed in your garden. Since they also multiply vegetatively, you might want to prevent them from reseeding themselves, encouraging them to use their energy instead to grow their clumps so that you can divide them into new plants.
How to Divide Siberian Iris
You will notice that your iris clumps expand outwards each year until eventually the centers stop blooming. You should divide your clumps before they reach that point which is unhealthy for them. Spring is the best time to divide and replant your iris. Divide them by carefully digging up the rhizomes with a garden fork about a month after they finish blooming and cutting them apart. Replant the outermost, young rhizomes and discard the older center ones. Replant the rhizomes 18 to 24 inches apart with the tops at least one inch below the soil surface. If you are not going to be replanting your rhizomes immediately, keep them moist by storing them in bucket of water until you are ready to plant them. Smaller divisions can take up to two years to reach a size where they will bloom so be patient!
How to Grow Siberian Iris From Seed Outdoors
If you want to grow Siberian iris from seed, you can either direct sow it in your garden in the fall or start your seeds indoors.
To direct sow in your garden, plant your seeds ½ inch deep in late fall or early winter. Iris need a period of cold to germinate so you won’t see any seedlings until the following spring. Germination should occur at the same time as your mature iris is blooming. The seedlings will grow all summer and fall and bloom the following spring.
How to Grow Siberian Iris From Seed Indoors
To start your seeds indoors, you will need to cold stratify them. Soak the seeds for 3 to 5 days, then plant them ½ inch deep in containers with pre-moistened soil. Place the containers inside a plastic bag and then place the bag covered container in your refrigerator for 60 days. This mimics winter weather. The plastic bag is to ensure that the soil doesn’t dry out too quickly. You will need to check the moisture level in soil periodically and add water as needed to keep the soil moist. After 60 days, you can remove the container from your refrigerator. Some of your seeds may already have sprouted. The rest will germinate within days of being removed from the refrigerator.
You can plant your seedlings outdoors after your last frost. They will grow foliage only all summer and fall. You can expect flowers the second year.
How to Use Siberian Iris as Cut Flowers
Iris make excellent cut flowers. Harvest your flowers early in the day. Choose buds that are just beginning to open rather than flowers that are fully open. The buds will open in a few hours in the vase. Place your flowers in a bucket of tepid water until you are ready to create your arrangement. When you are ready to arrange them, re-cut the stems about an inch above the original cut at an angle. To ensure the longest life for your flowers, keep your arrangement out of direct sunlight. It’s also a good idea to place it away from drafty doors and windows. Be sure to remove dead and dying flowers promptly.
Siberian iris are smaller, more delicate versions of the stately bearded iris. They are easy to grow, relatively disease free, and don’t mind moist areas. They are a good choice if your yard is not suitable for bearded iris.
Questions & Answers
Question: Will Siberian Iris grow in Southern California?
Answer: It depends. Siberian iris are hardy in zones 2 through 9. What zone is Southern California? Regardless of the zone, Southern California may be too dry for them. Siberian iris prefers moist soil. They will not survive in desert conditions.
Question: Can you grow Siberian Iris in a pot?
Answer: It is possible to grow Siberian iris in a container, but the plants will not grow well and will have very few flowers. Iris of all kinds prefers to be in the ground where they will have room to expand. You will need a very large container because Siberian iris can grow up to 4 feet tall. In a smaller container, the plant will be top heavy and the container will have a tendency to topple over.
Question: Can you grow Siberian Iris as a house flower?
Answer: No, unfortunately, they are outdoor only. Our homes are too dark for most plants. The plants that are commonly grown as houseplants are shade plants in their native environments so they can endure the low light levels in our homes.
© 2015 Caren White
Caren White (author) on January 18, 2015:
Faith Reaper, I adore iris and grow as many as I can cram into my garden. Thanks for reading, commenting, voting, tweeting and pinning!
Faith Reaper from southern USA on January 18, 2015:
Thank you for this beautiful and informative hub here. I do love the Iris.
Up ++++ tweeting and pinning