Question: My irises are a jungle. They are growing close together and the leaves look terrible. Some leaves look dead, some are bent and crooked, and some have brown tips or holes chewed in them. What can I do to make my plants beautiful again?

Answer: Sometimes, as gardeners, we need to step back and take a look at our garden and how it has changed over the years. Sometimes our gardens experience growth too rapidly or are affected by the weather or insects.

Caring for iris plants can be easy if you follow a few basic steps. Irises grow from an enlarged underground stem called a rhizome. These rhizomes grow just below the soil surface and are the source of growth for fans of leaves, flowers, and the roots that anchor the plants.

Irises require the same good cultural care as other perennials. They need adequate water (moist but not wet) before blooming time. It is important to clean up both bloomed-out stalks and dead leaves, which will not only keep iris plantings looking better, but also reduces the chances for future pest problems.

Fertilization of irises is not always necessary for a nice garden display. Most irises perform well with one fertilizer application per year. Apply 1 to 2 tablespoons of a 5-10-10 or similar fertilizer just after blooming around each rhizome, being careful not to apply the fertilizer directly on the rhizome, which may cause it to burn.

Iris rhizomes multiply rapidly and may require dividing every two to five years depending on the growing conditions in your garden. The time to divide the iris is after blooming is completed. For best results, divide in late summer to early fall. Overcrowded iris will become increasingly unproductive, having fewer, as well as smaller, flowers. Dividing and replanting will enhance flower production and the health of your iris.

Irises are subject to pest problems such as the iris borers. The borer overwinters as eggs attached to the previous year’s iris leaves. The young borers feed on the leaves, leaving jagged leaf edges and distinctive water streaks in the leaves. Sanitation is the key to controlling the pest. Once the iris leaves have turned yellow, remove the leaves and compost them. A well-timed insecticide application might also be helpful.

Crown rot is another disease that can affect the rhizomes making them soft. There will be small round tan spots on the leaf bases and a foul smell. Removal of seriously infected plants is vital to the health of your garden community.

Iris leaf spot is a common fungus disease that attacks the leaves and occasionally the flower stalks and buds of iris plants. Once again sanitation is important for its control. Iris leaf spot appears as small brown spots with water-soaked margins near the leaf tips. After blooming, the spots rapidly enlarge and cause the leaf to die. It is most common in wet seasons, so planting iris in full sun and with proper spacing will help reduce leaf wetness and disease severity. It is truly a magical time when your irises bloom again in the spring.

Do you have a gardening question? Email, call, or visit the Douglas County Master Gardener Plant Clinic at douglasmg@oregonstate.edu, 541-672-4461, or 1134 SE Douglas Ave., Roseburg.

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