I planted my first named tall bearded iris in 1962 so the learning process began some 55 years ago. Keep in mind that growing bearded iris in the eastern United States is in many ways a totally different experience than on the west coast where the majority of tall bearded irises are produced today.
Bearded irises were first discovered in desert Middle East so keep this important fact in mind when making gardening decisions.
We get much rain here in the southeast and subsoil saturation is a common occurrence. The most important preventive measure is to plant your iris on an elevated ridge or mound of at least 12 inches. By bloom season the ridge will have settled to at least half its original height. This extra effort at planting time will be of great value in the iris garden. We have our soil tested and any fertilizer needed or organic matter that we choose is placed at garden soil level under the 12” ridges.
Here we plant our iris rhizomes exposed to the sun, rain and wind. In colder climates and those with scorching sunshine, the rhizomes need to be protected by a layer of soil over them.
Once the iris bug bites, new gardeners often order truckloads of advertised “topsoil”. (Where does one find “topsoil”?) Isuggest that you plant your first iris in the soil that exists on your property. Adding organic matter is always helpful, but if you choose that route, an ideal situation is to plant a cover crop the first summer, fertilize your cover crop with nitrogen for optimum growth (which leaches down into the soil quickly), thendeeply cultivate before planting the following summer. Your soil should then be in ideal planting condition!
Sprinkling commercial fertilizers on top of an iris bed is a waste of energy and money as the first rain will wash it away; even worse, it can wash into the plants and cause rhizome and foliage damage. Whatever fertilizer you choose, work it deeply into the soil so the roots can feed on it.
Irises will not grow and bloom well in shade. You will discover that the hotter and more miserable the scorching summer sun bakes your irisplantings the heavier your spring bloom will be. In the eastern U. S. constant watering in summer heat is risky but in serious drought will be beneficial. Do NOT water overhead until AFTER the sun sets and the temperatures drop below 80 degrees.
Irises like to be free of weeds and grass with plenty of sunshine and air circulation. . Hand weeding is best. Today herbicides are in wide usage, but keep in mind that in the moist, humid southeast, these chemicals dissipate slowly, particularly in heavier soils. Isuccessfully “spot spray” stubborn grass seedlings with a contact herbicide, being care to prevent drift as much as possible. You should also consider alternating/rotating pre-emergent type chemical herbicides, choosing those that target your most insistent weed and grass species at the time of treatment. A common error is excessive and too-frequent over-application which can play havoc with your soil and reduce plant growth—both rate of increase, width and height of iris foliage and size of iris rhizomes. Chemical contamination is a certain death to good soil!
The addition of organic matter is a positive plan. Aged manures provide exceptional accelerated growth AND weed seed aplenty. Covering loads of manure with a tarp for 8-12 months before application heat-kills many of the seed. Oat straw is a superb soil conditioner—much preferred over wheat straw. There are other good choices, but commercially bagged soil additivescan be expensive and ineffective. Good organic matter will break down quickly and provide positive soil aeration. Most recommendations include “side dressing” with a commercial fertilizer 6-8 weeks before bloom. It is rarely dry enough to cultivate and incorporate chemical fertilizers intoour soil in February and early March. I would remind you again that fertilizers spread on soil surfaces is a foolish waste of time and money.
Rotating your planting areas is ideal as iris are heavy feeders. Few own the acreage required for such rotation on a massive scale. Most of us have other life experiences outside our gardens. Learn which soil treatments and gardening habits yield the most success with your irises. Growing plants is not rocket science, but it does require dedication and constant observation to see which techniques give the best results.
If you want good first year bloom on your irises, seriously consider transplanting at the end of your bloom season in the southeast. There is a natural recovery/rejuvenation process in bearded irises that begins at the end of their exhaustive bloom season. Begin cultivating in fertilizers and organic matter 6 weeks after bloom to give your irises a jump-start on next spring's bloom.
Feel free to email us if you have a plant problem. There are occasional problems that require proper chemicals to eradicate a specific problem.
We can hopefully help you find a solution. Most important is learning to enjoy the Vitamin D dosage from the sunshine while caring for your plants.