There are many types of Iris. This article will focus on the types of iris that grow from rhizomes. They can be different in their size; from miniature to tall bearded, but what they have in common is the rhizome.
Planting your new Iris
Irises are really tough. In fact you will sometimes see them growing on old farmsteads long after the buildings have crumbled to rubble. Iris will thrive in most types of soil but the main key to healthy irises is drainage. Planting on a slope or in a raised bed can improve drainage if you have heavy soil. You can add course sand or compost to improve your drainage also. The ideal pH is a slightly acidic 6.8 but they are not too fussy about this. Please don’t attempt to adjust pH with lime of sulfur unless you have had a soil test that tells you how much to add. You can easily add too much.
It is best to plant new iris after they have bloomed. This is why we prefer to ship your iris in July, August or September. We sometimes bend the rules on this to save on shipping if you are ordering other types of perennials and want to save on shipping. Moving iris after bloom is really best for the plant though, and also, if we ship after bloom then we can be absolutely sure that we are sending you the right plant. We don’t recommend moving iris later than September because they must get their roots set before winter sets in, or they can easily be heaved from the ground. If you live in an area with very mild winters we possibly could extend shipping into October. They should be planted at least 6 weeks before the first hard frost in your area.
Iris need at least 6 hours per day of full sun in order to bloom well. Even more is better, but some shade may help if you live in a very hot climate.
If you live in a very hot area or have very light soil you could put a little soil over the rhizome; no more than an inch. Firm the soil to remove air pockets and then water well. Plant your iris about a foot apart. You could put them a little closer but you will have to thin them sooner.
Irises that have just been planted should be watered frequently until their roots are established. After they are established, it is better to water deeply, less often than to water frequently, but shallow. Really, unless you live in a very dry area or are having a bad year, iris do not need supplemental watering. If you over water they could rot.
We do not fertilize our iris, but if you do wish to fertilize use a low nitrogen fertilizer. This would mean that the middle number should be higher than the first number. If you use high nitrogen fertilizer you will be rewarded with nice leaves at the expense of flowers. It is, however, normal for them not to bloom well the first year after transplant.
Caring for iris
Iris can live nearly anywhere because they are very tough plants, but they will do the best if you keep their beds weed free and remove debris that lay on top of the rhizomes. If you use mulch, keep it off the top of the rhizomes, and as it decomposes, check to see if the rhizomes need to be lifted a little to keep them at surface level. Sometimes I use forks to do this by going underneath, without completely digging up the plant…just lifting it and pressing it back down.
Cut off the bloom stalks down to near the ground when all of the buds are done. Remove individual flowers and branches as they finish. Don’t cut the leaves if they are healthy looking. Do cut if they are browning or showing insect damage or leaf spot. In fall trim them to around 6 inches. Irises do not need winter mulch when they are established. If you live in the far north they could benefit the first year as their roots may not be as well established. If you do it use something like straw or evergreen boughs that will allow air circulation rather than something like leaves that will pack down and become a wet mess. Wait to apply winter mulch until the ground is frozen. Remove any winter mulch in fairly early spring.
The biggest problem that Irises can have is rot. The best treatment is prevention. Make sure the soil is well drained and debris is removed. This will prevent them from being too wet and prevent rot. If you do get some rot it is important to remove the rotted part right away. You can stick a serrated knife right in and cut it away, or try a spoon. Sometimes it is necessary to dig up the rhizome. Irises put on new growth each year so the “old part”, the part that is away from the leaves, may eventually shrivel up or rot. Remove these spent “middles” if they are no longer firm. If you have the plant dug up, allow the fresh cuts to dry for a few days before replanting.
Overcrowded irises stop blooming. Depending on the variety and the growing conditions, Iris may need to be divided every 4 or 5 years. They are also more likely to have rot problems if they are crawling on top of each other. Please refer to “planting” above for when and how to divide. I like to leave “forks” (one rhizome with to leaf clusters) attached and if there are small side shoots leave those attached to the main rhizome.
Bring the colors of the rainbow to your garden with these classic and care free beauties.