Gardening Help FAQs

Here are answers to some of the most common questions we receive about garden plants. You will find concise information on general gardening techniques as well as plant selection and care. For detailed information on specific plant pests and problems refer to our Common Garden Pests and Problems page.

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Horticulture Questions and Answers

How do I grow iris?

One of the most spectacular spring-flowering plants is the bearded iris. The multitudes of colors, reminiscent of a rainbow, gave rise to the name.

The bearded iris are categorized into three groups: tall bearded (20-48"), intermediate bearded (6-20"), and dwarf bearded (5-6") based upon height and also flowering sequence, the dwarfs flowering earliest along with daffodils and crocus, while the tall varieties flower last, around Mother's Day with peonies.

Culture of the bearded iris is simple and straight-forward. Plant in a sunny location where the soil is well-drained. The soil must be prepared by deep digging to create excellent drainage. Incorporate some organic matter such as well-decayed manure or compost to the subsoil, and ground bonemeal or lime can be added to the topsoil, as directed by a soil test. A balanced fertilizer can be applied and worked into the topsoil each spring if soil test results indicate the need. Graded sand or calcined clay can also be added to improve the drainage.

The best time to plant is late July through early September. Rhizomes are planted with the attached roots evenly spread in the soil and only half-covered as they prefer to be sun-baked. The plants are used to best advantage as clumps; so, be sure to place the growing points to the outside of the clump because they will continue to grow in the same outward direction and not crowd each other.

Water thoroughly if the soil is dry and every week or so for the next several weeks to encourage rooting. No additional cultivation is required; the natural rainfall pattern in the St. Louis area is typically adequate to support their growth.

Remove fading flowers on a routine basis to allow unimpaired space for opening flowers to develop and also thwart seed formation. After all flowers have faded, cut the flowering stem just above the leaves. As summer progresses, continue to remove yellowing leaves from the clump.

Iris are typically pest and disease-free, however, watch for potential infestations of borers in the lower stems and rhizomes. For more information on borers refer to message #3431 "Controlling Iris Borer".