Growing Bearded Iris In The Waterwise Garden

by David Salman, High Country Gardens Chief Horticulturist

Growing Bearded Iris is simple, straightforward, and easily managed by the beginner gardener or master gardener alike. The Iris family is a big one that includes numerous species and an uncountable number of hybrid cultivars created by Iris breeders around the world. One of the most widely grown species is the Bearded Iris.

The "beard" on a bearded Iris refers to the fuzzy growth at the center of the flower, where the "falls," or downward growing petals, meet the "standards," or upward growing petals. Bearded Irises come in a wide array of solid and multicolored combinations. They have been a favorite garden flower for many, many generations here in the US and in Europe.

Bearded Irises are easy to grow, and well-suited for dry gardens. They grow well across most of the US, with the exception of the Gulf Coast and the Deep South, where excess moisture and humidity can cause the roots to rot. 

For western gardeners, growing Bearded Iris is quite straightforward, as these tough, durable plants thrive in our dry climates. They require only occasional watering once established. When planted into fast-draining soils with full sun exposure, they are long-lived. They will multiply nicely to form showy blooming clumps.

Bearded Iris can be grown from potted plants in spring, or grown from bareroot rhizomes in late summer.  When planting in late summer or fall, be sure to get your bareroot Iris in the ground at least 6 weeks before the first average frost date in your area, to give them enough time to establish before the ground freezes in winter.

To plant Bearded Iris rhizomes:

• First, prepare the soil. Mix a 3-to-4-inch thick layer of compost,  a few handfuls of natural soft rock phosphate, and Yum Yum Mix into the top 8-10 inches of the soil.
• Plant so that the shoulders of the rhizomes are just above the surface of the soil. Don’t plant them too deep - Bearded Irises prefer shallow cultivation. 

In the garden, Bearded Irises are heavy feeders, and they need regular fertilization to bloom strongly and multiply. I recommend top-dressing with a mix of high-quality compost, Yum Yum Mix, and some soft rock phosphate or bat guano in the spring, and again about a month after they have bloomed. Scatter several cups of this soil-building mix in a ring around the clumps. Avoid high nitrogen chemical fertilizers, as it degrades the soil over time and promotes leaf growth at the expense of flowering.

When they stop blooming or the flowers are sparse, this is an indication that they are crowded, and the soil is low in nutrients and needs to be enriched.

In terms of maintenance, the best time to divide your Iris clumps is in August, every 3-5 years.

• To divide Bearded Irises, dig the plants out of the ground, shake off the soil.
• Cut the rhizomes into pieces with a sharp clean garden knife, and be sure to include a fan or two of leaves on each piece of rhizome. 
• If you have some dusting sulfur, dip the cut ends into it and let the rhizomes dry for a day or two in the shade so the cuts callus over.
• Replant as outlined above.

To complement your colorful bearded Iris flowers, it's advisable to plant other flowering perennial companions that bloom in late spring and enjoy drier soils and full sun.

• 'Mesa Peach' Blanket Flower (Gaillardia aristata)- The big, peachy-gold petals of 'Mesa Peach' go beautifully with any of the blue and purple Bearded Iris.
• 'Little Night' European Sage (Salvia sylvestris) is a natural fit to pair with Bearded Iris. 'Little Night' is a compact grower that should be planted in front of the Iris clumps, where its deep indigo-blue late spring flower spikes offer a stunning color combination and contrasting shape to the ruffled Iris blooms.
• 'Shimmer' Evening Primrose (Oenothera fremontii) has attractive green turning to silver foliage and bright lemon-yellow flowers to complement the Iris. 'Shimmer' grows to form a low-growing mat of foliage that contrasts nicely with the color and form of the sword-like Iris leaves.