This is the time of year that one question is asked about irises just about every time we pick up the phone or turn on the computer. The question is, when do we cut the leaves back on our irises? The answer is NEVER, except when you are transplanting your rhizomes. I wish I knew how that myth got started in the iris world. The leaves on your iris plants help in feeding the plant, so why would you want to cut part of it's food supply? The next line I get is, some of my plants have brown tips on the leaves in the summer and I don't like to look at that. OK, if you want to set there and cut one inch off of each leaf to make the clump look better, do it. The key is, I said one inch, not 6 inches. The more you cut off, the more you are cutting the food supply. One more tip, cut the bloom stalks out all the way to the top of the rhizomes, as soon as the last blossom fades away. This is very important, as the stalks left in place, can cause rot.
The next question is how much should I water my irises in the summer? The answer is, you don't water your irises in the summer. If you are east of the Rockies, that rule will be great. West of the Rockies, I will leave it up to you, but it is never good to push irises to grow when they should be resting. Unless you have found it just absolutely kills your irises in the west if you don't water in the summer time, I would not do so. If you do, I would do it sparingly, not on a regular basis.
I can hear the howling already. I know there will be a number of you that will say I water my irises all summer and I don't have any problems. The key phrase will be, YET. You are asking the plant that wants to go dormant and take a rest to keep growing. In warm climates, like California and Arizona, and perhaps southern Texas, this may be fine. My thought is, in colder climates, this summer growth will wind up being tender for the winter and your plants may develop rot problems. There is a reason that almost every iris grower in the US ships their plants to their customers in mid summer to early fall. It is because the plants are dormant and it shocks the plants less to ship them at that time.
Now for the surprise, you must water your rebloomers in the summer or you won't get rebloom in the fall. If you are reading between the lines here, a problem may have surfaced for some of you that grow both types of irises. How do I water my rebloomers and not my once blooming irises? You don't. Plant your rebloomers in one area and the once bloomers in another area at least 3 feet apart. Now, water the rebloomers and not the once blooming irises. Remember, your reblooming irises will NOT REBLOOM without extra water. Have you ever noticed how much better your rebloomers bloom in a wet summer and fall season? I wish I had a dollar for every time I am asked why my rebloomers don't rebloom and they tell me they never give them extra water in the summer. It is absolutely the key to rebloom. Also a little extra fertilizer 2 or three times a year will work miracles for rebloom. It must be a light nitrogen blend like, 6-24-24, 6-12-12, or 5-10-10. Apply in March, late June, and October for most zones. Colder climates may back the fall application up a month for the fall application and pass the summer application.
I don't care what how many times I give culture tips to iris customers, there is always an exception to the rule. I share with you what I have learned from 31 years of growing and shipping irises to every state and several foreign countries. You should benefit from these suggestions for iris culture.
Thanks for listening until the next time.
God bless you and your gardens and our country.
Comanche Acres Iris Gardens