May is often considered the month of the iris in the Mid-South. It is the state flower of Tennessee and belongs to a genus of 280 species. Most people, when thinking about irises, are referring to the flag or bearded iris, a commonly cultivated plant.

A lesser-known iris that has been grown in the Memphis area for many years but never really gets the recognition it deserves is Iris tectorum, or roof iris.

Historically, it was grown in Asia on thatched roofs, which is where it gets its common name. Growing on thatched roofs might suggest that it requires excellent drainage; however, it thrives in our clay soils and is one of the toughest, most adaptable, and easy-care irises. It can tolerate both wet and dry conditions, in full sun or part shade. In mild winters, its foliage can even remain evergreen.

The straight species blooms with purplish-blue flowers atop 18-inch, sword-like foliage that looks good all season. Iris tectorum ‘Alba’ is a highly prized white form. We have also grown ‘Wolong’ at the Dixon, which has larger lavender flowers with purple flecks. It received the 2010 American Iris Society Award of Merit.

Plant Delights Nursery offers two cultivars that boast larger flowers than the species: ‘Snow on the Roof,’ a superior selection of ‘Alba,’ and the violet-bloomed ‘Slippery Slope.’

Although difficult to source commercially, this easy-care, must-have plant for the Mid-South garden can be found at the Dixon plant sale, Friday, April 11, 9:00am - 4:00pm and Saturday, April 12, 9:00am - 2:00pm. We grow them from seed and have found that they will bloom in the first year. It is also a great plant to divide and share with friends.