Friday, May 22, 2020

Butterfly Iris, Iris spuria

Last summer I visited the Royal Botanical Garden in Hamilton for the first time in several years. I found impressive displays of early summer perennials and row upon row of peonies in full bloom, but the flowers that captured my imagination the most were the lovely combination of Iris spuria and Iris Sibirica in all their glory. 

In my home garden, I have several Iris Sibirica, but I don't have any Iris spuria. These delicate irises look like softly colored butterflies. Not surprisingly, I later learned that one of the many common names for this plant is "Butterfly Iris". 

 Iris spuria subsp. carthaliniae (white form)

Iris spuria is native to southern Europe, northwestern Africa and southwestern Asia where it can be found in damp meadows, marshes and salt flats. It's a tall iris that can grow to as much as 5ft. Iris spuria flower a couple of weeks after tall bearded irises so they can help extend the time period you have iris in bloom. They have narrow, grass-like leaves and flowers that come in a range of colors including lilac, white, purple, wine and brown. In the fall, Iris spuria produces a long hexagonal seed capsule. They easily self-seed and may naturalize to form big clumps.

Iris spuria 'Allegory'

Growing Conditions

Iris Spuria requires full sun in rich, well-drained soil. Too little light may inhibit blooms. While they like consistent moisture during the spring growing season, they do not like wet soil. Soggy soil encourages rot.

These irises are heavy feeders, so fertilize your plants in the early spring to encourage the best display of flowers.  When the blooms are spent, remove the flower stems right to the ground to help keep your clump of irises looking tidy and to provide good air circulation.  In summer, the growth of many Iris spuria slows as plants enter a dormant period. They do not require supplemental water during this time of rest.

While Iris spuria does not like being moved, they will become crowded after a few years and will benefit from division. Divide them every 3-4 years right after they flower. They may need a full gardening season to recover before beginning to bloom again.

Pests and Problems

Verbena bud moth, slugs, snails, whiteflies, and thrips can all affect these perennial, but iris borer is the most common problem. Remove and destroy any affected foliage or rhizomes. Leaf spot, bacterial blight and rust are additional issues that can affect the foliage. Soft rot of the rhizomes and crown rot are signs of poor drainage.

A lack of flowers may be the result of overcrowding, too little sunlight, too much fertilizer or rhizomes that have been planted too deeply.

Removing debris to encourage good air circulation and routine division is key to keeping your Iris spuria happy.

Companion Planting

The mix of Iris spuria and Iris Sibirica at the Royal Botanical Garden was just beautiful. Like Iris spuria, Iris Sibirica likes full sun and soil that is rich in organic matter. To learn more, please visit this post on Siberian irises.

Iris Sibirica 'Percheron'

Iris Sibirica 'Purple Sands'

As well as irises, there were a number of other perennials in flower at the RBG including Peonies, Baptisia, Salvia, hardy Geraniums, Columbine and Lupins.

Siberian Irises with Peonies in the background.


Peonies and tall purple Phlomis tuberosa 'Amazone' in the background.

Salvia x sylvestris 'Ostfriesland'

 Knapweed, Centaurea hypoleuca 'John Coutts'

False Indigo, Baptisia and Giant Fleece Flower in the background.

Plant Type: Herbaceous perennial

Height: 2-5 ft

Spread: 2-3 ft

Flower: A range of colors including lilac, white, purple, wine and brown. They make great cut flowers.

Bloom period: Late Spring/early Summer

Leaf: Narrow green leaves

Light: Full sun

Growing conditions: Rich, well-drained soil

Move or Divide: After flowering

Problems: Iris borers, verbena bud moth, slugs, snails, whiteflies, and thrips. Leaf spot, bacterial blight, rust and soft rot.

USDA Zones: 5-9


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