Iris Gardening Tips

Iris are easy garden plants to grow, with a little care they can be magnificent in your landscape. Whether you’re planting for the first time or looking to enhance your existing garden, here are some tips that will help you create the most beautiful iris garden possible.

Iris rhizomes should be planted in well-drained soil that is pH 6.5 or lower with high fertility and organic matter. A soil amendment such as alfalfa pellets is especially beneficial.

Planting

Plant irises in well-drained garden soil with plenty of sunlight and adequate air movement. Dig holes about three inches deep and space the plants about 12 to 24 inches apart.

Iris are a good choice for many flower gardens because they are relatively low maintenance and come in a variety of colors, including red, purple, orange, yellow and white. They can also be used as edgings or in informal beds.

Divide irises every 2-4 years, or whenever they become crowded. This helps keep the clumps small and stress-free, and it encourages new blooming growth.

Before planting, amend the soil with a generous amount of compost or manure and bone meal. If the soil has a low pH, you may need to adjust it using lime or sulfur.

Watering

Irises can become very invasive, especially in dry areas, so it’s important to water them well during their first growing season. Specific watering information depends on your soil and weather conditions, but deep watering at long intervals is best.

It’s also a good idea to plant irises in an area where they will receive plenty of sunlight. This helps them develop their roots and rhizomes before winter.

In the fall, trim back iris foliage to within a few inches of the rhizome. This will help control the spread of borers and leaf spot fungus.

Fertilizing

Regardless of the type of iris you are planting, fertilize regularly to help the flowers grow. Most irises need a light application of a slow-release fertilizer in early spring and again a month after bloom.

Iris thrive in well-drained soils that have a moderate amount of moisture, but excess water can cause the rhizomes to rot. Avoid allowing the plants to stand in standing water for long periods of time; they will become sluggish and lose color.

Irises require plenty of sunlight, so be sure to choose a spot with at least six to eight hours of sun per day. Most irises prefer full sunlight, but they will also tolerate partial shade.

Pruning

Pruning is a common and essential practice that can be applied to most plants, whether trees, shrubs or perennials. It can be done for a number of reasons, including to control growth, encourage fruit production and manage the appearance of the plant.

Iris are no exception to this rule. They benefit from pruning when flowers fade and when foliage starts to die back.

To discourage rhizome rot, prune flower stalks down to the base at the end of the blooming season. Use a pair of pruning shears or clippers to trim each fan-shaped group of leaves down to half their height and angled so that rainwater will run off the cut surface rather than sitting on it.

Fall cleanup is also essential to limiting the presence of pests that overwinter on iris foliage. This includes removing the eggs of borers and the spores of leaf spot fungus.

Disease Control

Iris are incredibly easy to grow and are a great choice for those with minimal time and resources. But they also need careful disease control.

One problem iris can suffer from is iris severe mosaic virus (ISMV). This virus can adversely affect bulb-forming and rhizome-forming irises, as well as crocuses.

ISMV can be transmitted by aphids, which can feed on infected plants and then transfer the virus to non-infected plants. Identify infected plants and dispose of them immediately.

Other common problems that iris can face include borers and root rot. Both borers and rot can be avoided by practicing good garden practices, such as watering only during dry periods.