IN CALIFORNIA:
IN OREGON:
In our area, we have seen many old iris blooming in March and April. Many of these that grow like "weeds" are old varieties, and don't need any care.
The modern hybrid varieties are very fancy, and need more care. We who grow many varieties have great fun and a longer blooming season, with early, mid and late blooming iris giving us beautiful blossoms from about March into June. A few varieties rebloom, in late May or during the fall season.
In general, irises are hardy and can be transplanted anytime. The best time for planting is in late summer when they are semi-dormant. This gives them time to establish through the fall and winter, with higher probability for blooming the following spring.
After receiving bearded iris, it is better to plant as soon as possible. If not, store them is a cool dry area until planting time is available. They can survive easily being dry and cool.
When to Plant: Best time is August through late September.
Where to Plant: Bearded iris need at least 4 hours of sun, and more is better. Some afternoon shade is okay in a hot climate. They need well drained soil, such as raised beds, and neutral pH soil.
Soil Preparation: Iris will thrive in garden soils. Heavy clay soil must be improved by adding course sandy material (e.g. play sand, washed sand, etc.) and compost. Some sulfur powder will help neutralize alkaline. Prepare the soil by tilling or turning over the soil with a garden fork to a depth of at least 10 inches. Also some fertilizer may be added in tilling of the soil.
Depth to Plant: Plant iris so the tops of the rhizomes are at the surface, or barely covered, and the roots spread out and down on each side of a slight planting mound.
Distance Apart: Iris are generally planted 12 to 24 inches apart. They may be planted closer for immediate effect, but will need to be thinned out every other year.
Watering: Newly planted iris need some moisture to begin to establish their root system. But it should never be soggy, since it will increase possible iris rot. Let the soil dry before next watering. Periodic deep watering is more beneficial than frequent sprinkling. Rebloomers will like to have a little more watering to prepare for their rebloom.
Fertilizing: For iris in our area, we suggest a light feeding in mid October and mid February. Bearded iris don't like excess nitrogen fertilizer, since it will promote rot. Some suggested fertilizers are 10-20-10, or 13-13-13, or balanced organic fertilizer. Some other fertilizer recipes are also suggested by experts. The fertilizer is applied as a light top dressing, and possibly stirred a little into the top soil. Iris will respond well to a minimum of attention, while they may not thrive with no attention.
Thinning: Generally, iris need to be thinned and divided about every 3 to 4 years. Crowded clumps may slow down blooming.
General Care: We suggest to clean weeds and debris. Iris don't care for mulch on the top soil. Stalks can be cut close to the ground after bloom. Do not cut back healthy leaves, but diseased or brown ones should be removed. Keep diseased foliage out of the compost pile.
You should never mulch bearded irises if you want to keep them healthy. Mulch causes iris rhizomes to rot. It seemed to me that some weed-control products will safely eliminate weeds in irises, so I called the president of an iris society in another state. She looked in her American Iris Society yearbook and said Preen can be used. Youre probably familiar with Preen, since its widely advertised and often seen in garden centers.
Irises have to breath, so never cover them with mulch or anything else. They want an alkaline soil rather than an acid one. In the spring, do not cultivate too closely to the rhizomes. Wood ashes, high in potash and phosphorus, can be beneficial to an iris bed.
Actually, iris come in both bulbs and rhizomes - and there is a difference.
--Dutch iris, iris reticulata and iris danfordia (there are others) are bulbs. Bulbs are modified BUDS surrounded by thick fleshy layers, like an onion. They are normally globular in form. They often have either a smooth papery outer layer or one that looks more fibrous. Roots emerge from the bottom (basal plate) when the bulb is actively growing. Offsets are produced off this basal plate. Bulbs tend to "stay put" where you plant them, spreading very slowly over many years.
--Bearded iris (Germanica), Louisiana iris, Siberian iris, iris tectorum, iris cristata, spuria iris and aril iris (there are others) are rhizomes. Rhizomes are thickened STEMS that grow horizontally just below the soil surface. Rhizomes are normally elongated. They are solid, and may be smooth (Germanica, aril) or appear to have segments ringed with fibrous 'hairs' (Louisiana, spuria, Siberian). Roots are produced along the length of the lower surface. Offsets are normally produced at the growing points on the heel of the rhizome, but can occur anywhere along the rhizome. Rhizomes creep along under the surface and can spread rapidly, depending on the type of iris and the cultivar.
--Both bulbs and rhizomes (along with corms and tubers) provide the plant with the same service of storing nutrients for growth, only they do it a bit differently.
There are a wide variety of iris classifications. The general categories are bearded and beardless.
The classification list below is brief. For more information, you may go to some national iris web sites, or visit our local events and ask questions.
-Bearded iris:
The "Tall Bearded" (TB) are most common bearded, with an average height of around 36".
Different varieties have different heights and different blooming times in our spring season.
The "Median" types have several classification categories, and heights are less than 28".
Various types have different heights and blooming times, many bloom earlier than TB's:
The "Arilbred" types are a hybrid between the common bearded irises described above and the more exotic regelia and oncocyclus aril irises of the middle east and southern Asia. The less aril content, the more similar they are to growing TBs.
Bearded iris need some cool winter time to be happy for spring growing and blooming.
-Beardless iris:
The "Louisiana" (LA) are most common beardless, with height ranges similar to tall bearded. Varieties bloom over the range of mid April through mid May in our area. These need more moisture, and less need for cool winter.
The "Spuria" (SPU) type have some growing similarities to bearded iris, blooming with the late TBs and the LAs. They resemble Dutch iris on steroids, growing to heights of over 40" and producing pampas grass like clumps.
Others: "species", "Siberian", "Japanese", and a few others.
-Bulbous iris:
The "Bulbous" iris (e.g. "Dutch Iris") have a bulb-type base rather than rhizomes and bloom very early. Like most bulbs, they die back in the summer and come back in the fall/spring.
Reblooming iris:
There are some bearded iris varieties that rebloom late spring and/or during the fall. Not everything that is labeled a rebloomer will rebloom in here. Check with your local growers for varieties that rebloom here.
We are an affiliate of the American Iris Society. The American Iris Society is the official register of rhizome iris, while Holland is the register for the bulb iris. Our focus and mission is for educational and scientific purposes in the study of all rhizome iris. One way that we teach is to put together shows for the public to educate about the many different species and hybrids that may grow in your area. These shows across the US and Canada are sanctioned and recorded by the American Iris Society. They are judged by teams of judges who have studied and passed tests over several years. The shows are separated into three divisions: Horticulture, Seedlings and Artistic.
What am I looking at? And why did that one get a ribbon?
In the Horticulture section you are looking at named varieties, which have been recorded and introduced by the American Iris Society. You are also looking at Species and Species crosses (hybrids) of iris that have properly named and registered. In this section we judge the ability of the exhibitor to grow, bloom, transport and properly exhibit a perfect, unblemished flower and stem. Holes, tears, and even fingerprints that you may not see but the judges do see, will mark a flower and stem down in ranking, blue, red and white. Each section within the Horticulture Section is then awarded best iris of that section, and then all best of sections iris are judged against each other for Best of Show.
The Seedling Section is comprised of flowers that have not been introduced to the marketplace. The judging in this area is totally different as the judges are looking for not a perfectly groomed flower, but a unique one. Is it an improvement on what is available in the market now? Is it a better or unique color? Does it have better branching or more buds? Here, only blue ribbons are given to the seedlings that the judges deem worthy. Then all the blue ribbon iris are judged against each other and the Best Seedling is chosen.
The Artistic Section is where we have some fun working with our favorite flower. We show people that yes, they do make a good cut flower for your home and encourage you to grow some in your home garden.
More information can be found at our website, www.Leotclarkirissociety.org.
By Carol Cullen, Chico, CA.
A fertilizer with low nitrogen (N), and higher phosphorus (P), and potassium (K) is good. Broadly speaking, a 5-10-10 ratio is about right for most flowering plants.
Mixing Alfalfa and Iris, from "Iris in Canada" https://www.cdn-iris.ca/mixing-alfalfa-and-iris/