Summer days, summer gardens. Most enjoyable. For the Tall Bearded Iris in your garden, summer is also the perfect time to grow, to expand, to be transplanted.
Bearded Iris experience two root growth cycles in their annual growing cycle. The springtime growth we all eagerly anticipate in our Iris beds begins with the lengthening of the foliage upward and the root system outward. The rhizome uses its stored-up nutrients.”….As the bud swellings appear in the new fans there is a quickening of the new roots that will supply the plant with nutrients for new growth during and after bloom. The old roots from the previous year’s growth then wither and decay.” ( The World of Irises, p 314) After the springtime color display of full bloom has passed for the year, the underground development begins in earnest.
The Iris revel in the long summer days. During the six to eight weeks post bloom, the plants absorb the necessary nutrients for next spring’s growth and bloom. The rhizomes send out new increases which will become new self-contained, self-supporting rhizomes by early to mid-July. Once the summer growth is complete, the Iris takes a well-earned rest. Enter the gardener, spade in hand, plan in mind. Now is the time to dig, divide, share and transplant.
Here, in the Willamette Valley our Iris bloom season ends early- to mid-June. Therefore, at Schreiner’s Iris Gardens, we begin digging our fields early to mid-July. On a smaller scale in your garden, consider digging your Iris to transplant this summer if the clump is three to five years old. Share the divided Iris not only in your own garden, but also with the neighbors, friends and family….garden clubs, retirement homes, 4H clubs, and so on. Allowing Iris clumps to become over grown can lead to poor or no blossoms, smaller and smaller rhizomes, and outbreaks of rhizome-based diseases (such as bacterial soft rot).
Remember that the latest date for transplanting depends on local conditions. Newly planted Iris require a minimum of 6 weeks to set their new roots. Thus, they should be in the ground a minimum of six weeks before the first hard frost. Consult local resources to determine the frost dates in your area.
So, how do you go about digging and dividing the Iris in your garden? Visit our “How to Grow Iris” pages for more details and images on dividing and caring for your Iris! Take a look at another great Iris care resource, “A Guide to Bearded Irises: Cultivating the Rainbow“, by Kelly D. Norris.
What’s happening in the July garden? To trim or not to trim the foliage…Depending on your location, you may have a handful of lingering Iris blossoms, or all of your bloom stalks might be sporting the papery remains of the seasons’ blooms. When all blossoms on the stalks have finished, carefully trim the bloom stalk at its base. Leave all green foliage, though, in place. They offer an elegant vertical visual throughout the garden. You may remove any browned and dry leaves. Keep the Iris beds clean and free of weeds. Well-established Iris plants are drought tolerant. Newly planted Iris, though, do require a good long drink approximately every 7 to 10 days if the weather is very dry. Reblooming Iris also prefer irrigation between the spring bloom and summer/autumn re-bloom times. We recommend an application of a low-nitrogen fertilizer (such as 6-10-10) approximately one month after blooms have finished. Superphosphate and bonemeal also work well as a fertilizer for Iris.
Summer brings the promise of long days enjoying our gardens and all aspects of our lives. The season also brings with it our annual Summer Sale. You’ll find over 300 varieties of Tall Bearded Iris at deeply discounted prices.