It's a magical time when bearded irises unfurl their pencil-slim buds to reveal a kaleidoscope of color in spring. Once commonly called flags, these perennials flourish in Zones 3-9, where winter temperatures dip below freezing and allow the plant to go dormant before next year's growth. Next to roses, the iris is my all-time favorite flower. They are fragrant and the blooms have an iridescent quality to them. A serious cottage garden must have irises.
Bearded iris is among the most elegant -- and easy to grow -- flowers of spring. Follow our tips for long-lasting, ever-multiplying blooms. Bearded irises are relatively easy garden plants to grow and will give good results with a minimum of care, but like all plants, the better the culture the more magnificent the display.
The following instructions are easy to implement and should lead to beautiful iris blooms year after year.
Planting Bearded Iris
1. Soil Preparation:
Iris will thrive in most well-drained garden soils. Planting on a slope or in raised beds helps ensure good drainage. If your soil is heavy, coarse sand or humus may be added to improve drainage. Gypsum is an excellent soil conditioner that can improve most clay soils. The ideal pH is 6.8 (slightly acidic), but Iris are tolerant in this regard. To adjust the pH of your soil, lime may be added to acidic soils or sulfur to alkaline soils. It is always best to have your soil analyzed before taking corrective measures.
2. When, Where and How to Plant Bearded Iris Rhizomes:For best results, Iris should be planted in July, August or September. It's imperative that the roots of newly planted Iris be well-established before the growing season ends. In areas with hot summers and mild winters, September or October planting may be preferred. Iris need at least a half day of sun. In extremely hot climates, some shade is beneficial, but in most climates Iris do best with at least 6 hours a day of full sun. should be planted so the tops of the rhizomes are exposed and the roots are spread out facing downward in the soil.
Step (1) Build up a small mound of soil in the center of the planting hole.
Step (2) Center the rhizome on the soil mound and spread out the roots on either side.
Step (3) Firm the soil around the roots. Newly planted rhizomes should be watered thoroughly.
Be Patient -- Irises are perennials and require time to grow. New growth may be noticeable within 2-3 weeks and begins with a new center leaf in the fan. Depending upon the maturity of the rhizome and the geographical location, there may or may not be blooms the first Spring. In very light soils or in extremely hot climates, covering the rhizome with 1 inch of soil may be desirable. Firm the soil around each rhizome and then water to help settle the soil. A common mistake is to plant Bearded Iris too deeply. Iris are generally planted 12 to 24 inches apart. Close planting gives an immediate effect, but closely planted Iris will need to be thinned often. Plants spaced further apart will need less frequent thinning.
3. Watering Needs of Bearded IrisNewly set Iris plants need moisture to help their root systems become established. Specific watering information depends on your climate and your soil, but keep in mind that deep watering at long intervals is better than more frequent shallow watering’. Once established, Iris normally don't need to be watered except in arid areas. Over-watering is a common error.
4. Fertilizing Bearded Iris
Specific fertilizer recommendations depend on your soil type, but bone meal, superphosphate and 6-10-10 are all effective. A light application in the early spring and a second light application about a month after bloom will reward you with good growth and bloom. Avoid using anything high in nitrogen, as nitrogen encourages rot problems. The soil type for your area will determine your fertilizer needs. Superphosphate, or a well-balanced fertilizer with an N-P-K ratio of 10-10-10 or 5-10-10 are recommended. Avoid anything high in nitrogen as it encourages soft growth that is susceptible to disease. Provide a light application in early spring and again a month after bloom . Place fertilizer around rhizomes, not directly on them. Alfalfa pellets (without salt) are extremely beneficial when incorporated in the soil around newly planted irises. Do NOT use Feed and Weed preparations.
5. Dividing Clumps
When irises become crowded, usually every three to four years, bloom will decline. At this time, old clumps may be thinned by removing several divisions and leaving a portion of the clump in the ground. A better practice is to remove the entire clump, replenish the soil and replant a few large rhizomes.
6. Caring for Your Iris Beds
Keep your Iris beds clean and free of weeds and debris, allowing the tops of the rhizomes to bask in the sun. Bloom stalks should be cut off close to the base after all buds have finished blooming. Healthy green leaves should be left undisturbed, but diseased or brown leaves should be removed.
Bearded Iris range from the small to the tall, with the shortest of them beginning to bloom as early as late March here in Oregon. The color spectacle continues into April with the emergence of the Median Bearded Iris, followed by the Tall Bearded Iris which begin to fade in early to mid-June. Bloom time for each variety lasts approximately two weeks, depending on the weather.
There are some Tall Bearded Iris that bloom early and some that bloom late, so try some of each to lengthen your season by a week or two. Consider some of the smaller bearded Iris, such as the Intermediate and Standard Dwarf Bearded Iris, as you can add a month to the beginning of your bloom season using these.