Irises are easy-to-grow perennials. Their flowers are breathtakingly beautiful, strangely reminiscent of those of orchids, and one can easily play the diversity card as there are so many cultivars available today. With the exception of scarlet red, irises come in an impressive palette of colors and tones, offering a irresistible spectacle spring after spring. Resistant and not very demanding, irises are suitable for all gardeners, even inexperienced. They grow over time, forming lavish colorful clusters. Alas, if we don’t take care of divide them regularly, their flowering withers little by little. Let’s see what is the best time of the year to split their irises and how to proceed.
Why divide irises?
After a few years, an Iris gradually loses its vigour. This leads to a weakening of its flowering which is no longer as abundant as before, nor as spectacular. It is generally in the center of the clumps that the flowers are less and less numerous when the rhizomes have gradually developed outward to the point of being more and more tight against each other. They end up running out of spacewhich is detrimental to their development.
If you don’t take care to divide your irises, the rhizomes get tired and can’t produce as many flowers. On the other hand, they begin to form more leaves, which is no longer of as much interest to the gardener.
When to divide your irises?
It is always during the rest period that one intervenes to split his tufts of irises. We therefore let the flowering period pass completely, and when the last flowers have faded and the stems are dry, it is time to intervene. Depending on the varieties and cultivars, the right time to divide your irises is between July and September. We do not delay too much because the division of the irises must absolutely be carried out before the dormant period.
Some gardeners prefer to anticipate rather than wait for the flowering of irises to be less abundant before deciding to split them. For the effect to be just as spectacular year after year, it is therefore sufficient to systematically divide those who have been in place for 4 or 5 years, and even sometimes for only 3 years once they have grown in size and begin to be tight.
What is the method for dividing or splitting irises?
During the summer, when flowering is over, the irises go to rest. We therefore take advantage of this special moment to give them more space so that they continue to flourish in good conditions and therefore to bloom profusely. This consists of dividing them by proceeding as follows.
- Bring a spade fork.
- Gently raise the earth all around the clump, taking care to plant your tines in the ground 15 cm from each Iris so as not to risk injuring the youngest rhizomes which have developed on the periphery.
- Use a lever movement with the tool to carefully lift the entire tuft then extract it from its location.
- Remove excess soil by tapping the clump against its boot or shaking it.
- Observe the root part. It consists of a slightly withered central rhizome from which other rhizomes start.
- Take a knife with a perfectly sharp blade and disinfect it by passing it over a flame, for example.
- Make clean, clean cuts with a knife to remove sections of rhizomes about 7 cm in length, each of which must have rootlets and a small tuft of leaves.
It remains only to prepare the pieces of rhizomes. The operation consists in possibly shortening their root hairs so that the rootlets do not exceed 5 cm in length, and in reducing the largest leaves to a maximum of 15 cm. It is recommended to deposit by dusting the charcoal powder on cut wounds. This naturally prevents fungal diseases.
We take advantage of it to remove damaged rhizomes, stunted, with holes or withered. They can be thrown in the compost. Only the very firm and healthy rhizomes can be kept in order to be replanted.
What to do with the iris rhizomes after the division of the clumps?
The pieces of rhizomes from the division of irises being ready, they must be replanted without delay. This therefore implies having already taken care to prepare their location. They are planted in loosened, draining soil, lightened with a little sand if it is heavy or clayey, always well enriched with compost and free of all weeds and their roots. They can also be installed in place of old rhizomes once the soil has been cleaned. Caution of don’t push them too deep into the ground, that is to say no more than three quarters. You should be able to see the back of the rhizomes.
After the establishment, we think of watering his irises copiously and regularly to ensure their recovery, especially since at this time of the year, the rains are generally rare and the temperatures can be very high. When new leaves show the tip of their nose, it is because the pieces of rhizomes have indeed resumed.
It is right to give them enough space : 30 cm for the large varieties, 15 to 20 for the smaller ones. Rather than replanting them online, the good idea is to form groups of 3, 5 or 7 feet in order to create colorful keysround, triangular or other in shape, whether in beds, in a rockery, on the edge of an alley (in this case we opt for two to three staggered rows), or for a slightly wild effect, in the lawn…
You should know that an Iris from the division may not flower the following year if it has been cut a little short. It will therefore be necessary patients another year, but well worth it. After a few seasons, all these pieces of rhizomes will in turn form large clumps tight to each other that will also need to be divided between July and September. All you have to do is replant them or give them away if you are sorely lacking in space.