Growing Bearded Iris by Mike Close

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Planting Guidelines: The best time to plant iris is late summer through early fall. Spring planting can often result in lack of bloom for a season or two and slow establishment.

WHERE TO PLANT:  Iris generally need at least half a day of full sun.

SOIL: Bearded iris need a balanced, well-drained soil but are very adaptable to a variety of soil types. If drainage is a problem raised beds can be should beused. Iris, like most perennials, prefer neutral to slightly acidic soil (pH of 6.8 – 7.0 is ideal). Heavy clays should be amended with sand to lighten the soil and aid in drainage. Till the soil and add some bone meal or a complete fertilizer. Mulch can be used to conrol weeds and aid in winter protection and water retention as long as the mulch does not cover the rhizome.

Planting: Don’t plant the Iris to deep. Spread the roots in the tilled soil and keep the top 1/3 of the rhizome above the soil(a little deeper if in intense sun all day) and cover the rest with soil and firmly pack to remove air, water liberally. Plant about 14-18 inches apart. This allows the new growth to fill the area between plants in about three to four years.

FERTILIZATION: Fertilizer will increase bloom size and number of blooms. Fertilize in mid to late March with bone meal, superphosphate, or a fertilizer low in nitrogen such as 6-10-10. When selecting fertilizers for irises, be sure that the 2nd and 3rd numbers are bigger than the 1st. These numbers stand for the amounts of phosphorus and potassium in the mixture. Phosphorus and potassium are the key nutrients in root and bloom production. Another dose of fertilizer at half strength after fall dividing and planting will slow release throughout the winter and early spring.

GENERAL CARE: After a couple of years iris will become crowded and blooms will suffer. In late summer dig up the clump divide the babies and plant as above. Discard the old plant because it will not bloom again. Also discard rhizomes with soft watery tissue and borer damage. Sometimes you will see new buds coming off the center rhizome. In that case you can replant as before. Keep the bed free of weeds by pulling and mulch as they do not like competition from grass and weeds. Iiris are VERY drought tolerant! Watering is only necessary under the most severe droughts.

Iris Borer:  When dividing the rhizomes inspect for soft spots and small holes. If present that is a sign that you have iris borer damage. Prune off those areas and discard before planting. Another sign of borers are dark streaks in the leaves. Clean up your beds in the fall after a frost to help control Iris Borer.