Growing Siberian Iris Flowers

Siberian iris is a hardy perennial characterized by its long, shiny, grass-like leaves and beardless blooms that appear in shades of white, yellow, pink, red, blue or purple. Flowers appear on tall, slender flower stalks in late spring through summer. Siberian iris foliage turns an attractive orange-brown in fall, providing a colorful accent until winter. These undemanding plants reach heights of up to 3 feet and require only minimal maintenance to thrive in USDA hardiness zones 4 through 10.

Site and Soil

Siberian iris prefers a planting site that receives full sunlight throughout the day. The plant can survive in partial shade, but flowering will be reduced. Apply a 2-inch layer of organic compost to the planting site and use a garden tiller to work the material into the soil to increase drainage and fertility. Manually remove any weeds from the site prior to planting to eliminate competition. Plant Siberian iris flowers in mid-spring to late summer.

Watering and Mulching

Water Siberian irises whenever the top inch of soil is beginning to dry, about once per week during the first year of growth. Reduce watering frequency to once every two weeks thereafter, except on weeks that receive less than one inch of rainfall. Apply water to the soil to avoid wetting the leaves, as moist foliage is more vulnerable to pests and disease. Do not water during winter, when the plant is dormant and requires less moisture.

Spread a 2- to 3-inch layer of mulch over the soil surrounding Siberian iris to further deter weeds and increase moisture conservation. Begin the layer of mulch several inches from the crown of the plant, or the area where the stem meets the roots, to allow adequate air circulation. Replenish the mulch whenever necessary to keep it about 3 inches thick year round.

Fertilizing and Pruning

Fertilize Siberian iris plants twice per year, once during early spring just as new growth begins and again shortly after blooming. Use an all-purpose 10-10-10 NPK fertilizer to provide proper nutrition for flowering and root formation. Water immediately after applying to release nutrients into the soil and prevent root injury from the influx of nitrogen. Apply according to the manufacturer’s instructions for the best results.

Prune plants twice each year, once during late fall and again during early spring. Remove all damaged, diseased, leggy or excessively long growth to increase the health of the plant and promote a compact growth habit. Cut off the targeted growth at its point of origin to avoid causing unnecessary damage. Remove faded Siberian iris flowers as necessary to improve the plant’s visual appeal and encourage further blooms.