Iris Tips and Care

Irises make lovely cut flower arrangements.

Irises make lovely cut flower arrangements.

Just as the rose, the dahlia and the orchid have exuberant fans along with societies, awards and special cultural secrets, so does the iris. The Iris genus contains over 200 species classified as either aril, beardless or bearded. The “beard” on the bearded iris is the caterpillar-looking growth on the lower petal. The iris is adored for its large, colorful, showy flowers that bloom, depending on type, either in spring or summer.


Irises aren’t fussy when it comes to soil. While the plant does best with a soil pH of 6.8, it tolerates both higher and lower ranges. The only requirement that must be met is well-drained soil. If you have heavy, clay soil, either amend it with lots of organic matter or create raised beds for the irises. This way you can control not only the soil type and texture, but, because you won’t be walking on the iris bed, you avoid the soil compaction that occurs while working in the garden.


Plant beardless irises, such as the Japanese iris, in the fall, and plant bearded irises in mid-summer. How deep to plant the iris rhizome depends on its size. A rule of thumb is to plant the bearded iris deep enough so that the very top of the rhizome is exposed above the soil. Plant Japanese and Siberian irises 2 to 3 inches deep. Dig the planting hole wide enough so that you can fan out the roots on the bottom of the hole and then pack the soil around the rhizome. Plant irises 12 to 24 inches apart


Water the newly planted iris slowly and deeply after planting and until it becomes established. This is a crucial period when the roots are growing, so don’t allow the soil to dry out. A soaker hose placed in the iris bed is ideal for delivering water slowly. Once the bearded iris is established, it typically won’t require supplemental water unless you live in a dry climate. Japanese and other beardless iris require consistently moist soil, especially in the three weeks leading up to bloom.


Apply the season’s first fertilizer -- 5-10-10 -- in spring, and make another application one month before bloom. Dig a 2-inch-deep trench, 2 inches to the side of the row of irises, and sprinkle the fertilizer granules along the bottom of it. Fill the trench with soil, and water slowly and deeply. This type of fertilizer application is known as side-dressing, and it is used to avoid burning the plant’s roots. In late September, sprinkle a handful of bone meal on the soil around each iris plant, and water it in.


After several years, you may notice that your iris plants have crowded together. This sets up conditions conducive to disease, so you need to thin the plants. The best way to do this is to dig up the plants, remove the new rhizomes, and replant them. When the flower fades, cut the entire stalk to the soil and remove it from the garden. It’s important to not allow debris to build up on the soil to avoid insect problems.

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