General Culture & Care

The links below provide additional information about iris culture and care, although most is not specific to our region:

Recommended Pesticide: Bayer Advanced 2-in-1

























Iris Culture and Care in Kentucky

Irises will thrive and reward you in Kentucky, with a minimal amount of care. With 6+ hours of sunlight each day and soil that dries out regularly, most irises will grow and multiply easily, offering beautiful blooms each spring (and sometimes in the fall).

When you plant your iris rhizome(s), you’ll want to plant them with only a minimal covering of dirt over the rhizome. Once the plant is settled, the top of the rhizome should be at soil level, exposed to the sun. If planting more than one of the same type, you can plant two or three of them together in a new clump, but make sure the “toes” are facing each other and the fans of leaves as far apart as possible. Each rhizome (or new clump) should be 12-18” apart. When planting the iris, it is good to mix in a fertilizer like 5-20-20 to encourage root growth. You may also need lime to balance the soil pH to a neutral 7, if indicated by soil tests. Keep them lightly watered over the next several weeks, and then let nature take its course.

In the fall, established irises may benefit from additional fertilizer. You should use fertilizer without much nitrogen; or if you use one with nitrogen, find one that has sodium nitrate instead of ammonium nitrate (sodium nitrate doesn’t last as long, so it doesn’t encourage growth in late fall, when the iris should be entering dormancy). Reblooming irises in particular will need this additional feeding, since they can grow almost twice as fast as most irises, which bloom only once a year.

During the winter, you can mostly forget your irises. It’s OK if they accumulate some leaf litter around them, as long as their leaves are still exposed to the sunlight. In February or March, as new growth is just beginning, clear away this debris, cut off or gently pull off dead or diseased leaves, and make sure the rhizomes aren’t buried in soil.

This is also the best time to fertilize irises – you’ll remember to do this when you see crocuses beginning to bloom. Use a balanced fertilizer like 10-10-10, but nothing where the first number (nitrogen) is greater than the others.

Springtime is also the best time to prevent iris borers, the most destructive pest that affects irises. It is the larva of a moth, and it eats into the rhizome and destroys it from within. While pesticides should be used judiciously, they are the most reliable method for preventing a borer infestation.

The most effective borer prevention insecticides contain Merit®, also known as Imidacloprid. It can be found in garden supply stores and home improvement stores, often combined with a fertilizer. Use it every 6 weeks or so until summer, especially right before the irises start blooming.

Kentucky’s blooming season starts in mid to late April and continues through the end of May, more or less. In normal years, peak bloom for TB irises is around May 10-20. Once a stalk is completely done blooming, remove it at the base of the plant with a clean cut or break.

In the summer, keep the plants free of weeds so the rhizomes see the sunshine. Keep removing dead or diseased foliage, but never cut back or remove healthy leaves unless absolutely necessary, or unless transplanting. Dispose of diseased iris foliage off of your property, so you don’t create a breeding ground.

July is the best time to divide, share and replant irises. Only rhizomes that have not yet bloomed will produce flowers next year. These are usually younger rhizomes that have budded off of an older rhizome. When sharing, gently remove the dirt and wash the rhizome in water that has a small amount of bleach in it (to kill any diseases or pests). At this time it is OK to cut half to 2/3 of the foliage off. Replant the iris with 12-18 inches of space around it in all directions, with the top of the rhizome even with the soil surface. See further instructions above for replanting.

A small fraction of irises will naturally rebloom in the fall. If you’re lucky enough to have one or more of these, just treat them with a little extra fertilizer and water during the early fall. Make sure to cut off spent bloom stalks in the late fall, even if everything around it seems dormant – this prevents rot, and helps to set you up for another great bloom season in the spring.

Watch this video to learn how to dig and divide your irises...


More Iris growing tips...

Tips from Winterberry Iris Garden (a hybridizer in zone 6 like us)

Tips from the Missouri regional site

Tips from Abbey Gardens