Bearded Irises tend to get bushy every two to three years and cease to produce good blooms. Dividing and transplanting allows the clump to renew itself and also provides a way to multiply your Iris. It is not difficult to do, but it is important to do it at the right time of the year to ensure that the Iris benefits the most from the division.
Steps
Step 1. Choose the right time of year to split
The best time for division of bearded irises is after flowering, so much so that the recovery of each plant will occur quickly. This could be between late spring and early summer, and until early August in the northern hemisphere. Do not divide during periods of dormancy (winter period), because the plant is trying to survive on the energy stored in its rhizome.
Step 2. Get to know the Iris
Since the division can differ slightly between Irises, it is important to know which Iris you are trying to divide. This article refers to the bearded Iris, the best known of the Irises. If you are using it for other Irises, be aware that there may be delays in flowering. For example, bearded irises have rhizomes (roots) that grow on the same spot every season and do not like to be moved. If you move a Bearded Iris, it probably won't bloom in the following season.
Step 3. Dig up the clumps of the Iris or part of them at a time
Use a spade or rake. Note that clumps can be heavy, so it's a good idea to have some support available. Shake or remove excess soil from the roots with water.
Step 4. Break and separate the larger clumps
The rhizome should easily separate at a joint.
- Choose firm rhizomes that have roots and a clump of leaves. Discard (and do not compost) rhizomes that appear to be yielding or limp, because they could be rotten or sick.
- This is a good time to get rid of lifeless foliage, and larger, older leaves that can tip the plant over before it forms new roots. Keep most of the foliage.
- You can break the rhizomes with your hands, or use a sharp knife to make a sharper cut.
Step 5. Dig an area where the Irises need to be replanted
Form a mound in the center and place the rhizome on top of this. Spread the roots into the hole.
Step 6. Pour some soil around the root and compact
The earth should reach the top of the rhizome. It's okay if the rhizome is partially exposed.
Bearded Irises appreciate a calcareous soil, so get it if needed
Step 7. Space the rhizomes 10 to 15 cm apart and make sure the clumps point in the same direction
Some experts suggest spacing them 30 cm or even 60 cm, especially if it is a tall bearded Iris. When you decide how far to put them, consider how dense you want the flower bed to be, and after how long you will still divide the Irises.
Step 8. Water thoroughly after planting
Water well every week until autumn to start the flower bed. Infrequent but deep water is better than more frequent but shallow water. Irises are reasonably drought tolerant, but too much water can promote rot.
Advice
- Plant the small shoots and rhizome fragments to maximize propagation. Shoots will form; although these will not bloom the following spring, they will become quality divisions in the summer.
- Don't be intimidated by this process. Bearded Irises are quite hardy plants and can tolerate being dug up every now and then. On the other hand, if they are not divided, they will eventually cease to bloom or have little flowering.
- Tie thin colored ribbons on the stems of the buds while they are in bloom, so you can identify colors for multi-colored flowerbeds during division.
- Eliminate weed growth by using a 5cm layer of compost or decaying manure.
- Some cut green leaves when dividing bearded irises, but this is not necessary. Remember that the leaves feed the rhizomes, so it may be preferable to leave a certain amount of foliage intact.
