A gardener writes in: My Iris are just about finished blooming. The plants are very crowded and overgrown. What’s the best way to prune/thin this area of my garden.Thanks!
The short answer is this: First – find a friend who wants some of your bulbs. Second – start ripping.
The longer answer includes a few tips: Irises are like bunnies, if you’re not careful, you’ll have a yard full of them in no time. I should know, I started my garden with 8 iris bulbs that I took from my parent’s house and last year I gave away over 30 bulbs and still had probably 50 in my garden.
Irises are above-ground rhizomes which sit on the soil surface and send roots down into the ground. They also form baby rhizomes on either side of their long root base. I’ve seen as many as 5 new irises forming off one base plant. They are extremely hearty plants that can tolerate dividing very well, and this is the perfect time to do it. Simply break off the new rhizomes from the base plant and either toss the base plant (if it is looking withered) or keep it and replant. Give the baby plants away to your friends, if you are just looking to thin out your garden.
If you’re looking to expand your iris garden, plant new rhizomes with several inches of space around them, and bury them with the tops of the rhizome showing above ground. Cut the foliage back to about 4 inches – like a crew cut. This will force the plant into root production. Water deeply and regularly until they are established. New plants can take several years to flower, depending on how cold your winters get.
One important thing to know about most bulbs and rhizomes is that when they finish blooming, resist the temptation to cut back the foliage until the leaves have turned brown. As the foliage dies back and turns brown (yes, and completely unattractive), the rhizome is using that energy from the leaves to begin storing up for next year’s bloom. Cutting the foliage before this point will weaken the plant and make for a less than stellar blooming season next year. Cutting back the flowering stem is perfectly alright, in fact, encouraged. Some people braid their dying foliage, but again, that is discouraged because it deprives the leaves of sunlight needed to produce energy. The best thing to do is companion-plant your irises with other bulbs that bloom later in the season, or with perennials that have something green going on all year long.
Once the foliage has turned brown, you can crew-cut them as described above. I recommend this for Irises only. Other bulbs generally don’t like to be cut.
For more information on Irises, visit: http://www.irises.org