Cultivation Of Siberian Irises
CULTURE and TRANSPLANTING of SIBERIAN IRISES
Generally, the keys to success with Siberians are transplanting in good garden soil, allowing at least a half day or more of full sun and most importantly, keep the plants moist until they are well established
in their new location. Better to over-water than to let the soil around the transplants dry out at transplanting.
These hardy perennials usually grow from 2' to 4' tall in zones 3 - 9 and bloom about the same time as Bearded Irises. Their lovely flowers and continuing narrow upright foliage are assets in the garden or border all season until frost. Siberians are excellent too as cut flowers. New transplants however usually do not bloom until their second full season. If possible, before receiving the plants check the pH of your soil and amend to 5.5 to 6.5 which is optimum. Iris borers and a few other minor insect pests are best controlled with a systemic insecticide (such as Isotox or other grub control) used in accordance with the manufacturer's recommendations. Diploid or tetraploid Siberians are both handled in the same manner.
Siberian Irises are shipped shortly after being dug, often with their roots moistened to minimize shipping and transplanting shock. When received, the new divisions should be removed from shipping boxes and planted as soon as possible. If planting must wait until the following day, unwrap the plastic bags and rewet the roots draining excess water. Re-secure the bags to preserve moisture around the roots. Keep the plants out of direct sunlight prior to transplanting. New plants may have their roots soaked by standing immersed in water, out of the bags, for an hour or two before planting in the ground. Potted up divisions should be kept well watered prior to transplanting in the garden.
Plants should be set
with roots well spread out and down in the new prepared hole, with the top of the rhizomes about 2 inches below the soil surface when finished.
Allow 15" to 24" spacing between plants. Liberally apply water to new transplants and mulch if possible. New transplants should not be fertilized until they are well rooted, often 2 to 3 months. Siberian Irises are not very heavy feeders. Good compost or a light application of a general purpose fertilizer (5-10-10 or 10-10-10) scratched in around the plants after flowering is beneficial. Mulch, or even extra soil mounded up over the plants just before hard frosts, is an especially good idea for the winter in cold areas to keep the new plants from heaving out.
Old plants can be lifted, then divided and replanted when their flowering declines, usually in 4 or 5 to as many as 8 or 10 years. After lifting, thrash soil out of the roots. Two spading forks may be used back to back to break the large clump apart for transplanting. New divisions may be torn off by hand or cut with a serrated knife and should be 4 to 8 fans average, never a single fan. When dividing, cut the foliage back with scissors to about 8" tall and break off the old root systems leaving only the newest piece of rhizome with it's feeder roots. The root systems may also be cut back to 4 to 5 inches to make transplanting easier. If planting in the same place, properly amend and refortify the soil with good compost and humus before replanting. Extra plants may be potted up, watered and given to gardening friends.
Transplanting is best during the spring in zone 3,4,5 and during early fall in zones 6-9.
Although, transplants kept well watered
may be made most anytime, except in the heat of mid to late summer. Seedpods not hybridized, should be picked before the seeds are spilled naturally in the fall, so inferior volunteers do not grow among the plants. After the foliage dies in the fall, cut off near the ground and remove from the garden. This may help eliminate winter cover for rodents. Once established, Siberian Irises require little maintenance and are among the hardiest of all perennial plants. Enjoy.
DUNLOP & COLE Originators & Breeders Since 1993 www.FieldstoneGardens.com
-- Main.RPries - 2010-01-08