The Q&A Archives: Some Reasons Why Irises Don't Bloom

Question: I have a lot of iris beds with bearded, Siberian, Japanese

Answer: Bearded iris need to be divided every 4-5 years to keep their vigor. If you have just divided them, wait. They will begin to bloom again. All irises bloom best in full sun, but soil, moisture and climatic requirements vary with the types. Bearded irises do well in zones 3-10 and will grow in any well-drained soil. Louisiana irises grow best in zones 7-10, Japanese iris in zones 5-8 and Siberian irises in zones 3-8; Louisiana, Japanese and Siberian irises require acid soil (5.5-6.5). Both Louisiana and Japanese irises do best in very moist soil liberally supplemented with peat moss, leaf mold or compost. Siberian iris thrive in moist but well-drained soil. Siberian, Louisiana and Japanese iris can be left alone for as long as 8-10 years, when they may become overcrowded. Be sure the plants are receiving FULL sun.

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