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Irises |
By Margaret Page Culver, Colorado Master Gardener, Colorado State
University Cooperative Extension , Denver County
Complex hybridization has resulted in an astounding variety of irises to choose from. And,
with careful planning, Colorado gardeners can extend the bloom time of iris over many
months in their gardens.
Their lovely flowers are available in every color and color- combination imaginable. Little wonder that early botanists named this beautiful flower in honor of Iris, the rainbow goddess.
Iris flowers are characterized by their unique shape. The three outer
sepals of each flower are called “falls,: and have a fuzzy central portion called a
“beard.” The inner petals are upright and called “standards.” The
edges of the petals are sometimes ruffled.
One of the earliest bloomers, in late February to early March, is the bulbous reticulata
iris, Iris danfordiae. This tiny iris, four to six inches in height, bears a
single yellow flower. Its falls are sprinkled with greenish-grown “freckles.”
Blooming so early, it calls out to the winter-weary gardener, “Spring is coming!
Spring is coming!”
A few weeks later, in mid to late March, several other species of reticulata iris make
their appearance. Most of these are in the color range of purple, indigo or sky blue.
Varieties commonly available in Colorado nurseries are I.’George,’
which bears sturdy rich purple flowers, I.‘Harmony,’ which produces
royal blue flowers with a central yellow mark on each fall, and I. ‘Histrioides,’which
bears dark blue flowers. The falls of I. ‘Histrioides’ have deeper blue
spots on them and have a yellow center ridge.
Iris reticulata (photo by Carl Wilson)
Plant Iris reticulata bulbs along with crocus bulbs for heavenly early
spring spot in your garden. Iris reticulata bulbs are available in the fall in
neighborhood garden centers. They should be planted two to four inches apart at a depth of
at least twice the size of the small bulb.
In mid-season, just as deciduous trees begin to leaf out, dwarf irises (eight to twelve
inches tall) begin to bloom. These beauties, planted in front of a perennial border or in
a rock garden, offer a wider spectrum of color.
Varieties usually available in Colorado nurseries include I. ‘Chubby Cheeks,’
that bears ruffled, light violet-edged white flowers with tangerine tipped violet beards.
Also, I. ‘Cotton Blossom,’ that offers ruffled creamy white flowers, I.
‘Dark Vader’ with ruffled, dark blue-violet standards and black falls with
violet beards, and I. ‘Eyebright’ that produces bright yellow flowers.
Its falls have deep down brown lines and deep yellow beards.
Throughout May and June the more familiar bearded irises (above photo), sometimes called
“German irises,” break into bloom. These glorious flowers, growing up to three
or four feet in height, come in a rainbow of colors too numerous to describe.
Intermediate, border, and several tall bearded types sequence through the blooming season.
These are followed by beardless Siberian, Spuria and Japanese iris that bloom through mid-summer. All together, the many types of iris offer at least five months of bloom.
Siberian iris
Since there are several iris farms in Colorado, it may be best for
gardeners to visit one when the bearded irises are in full bloom. That way a gardener can
spade up and plant irises that correspond to the color scheme of their garden. Given the
glorious array of colors, the temptation in visiting an iris farm is to buy more plants
than are actually needed.
Irises bloom best when they are planted in full sun. They are drought tolerant and do well
in xeriscape gardens. Each rhizome (the fleshy root-like stem) should be set in a shallow
hole so that the top of rhizome is one inch or less beneath the soil.
In perennial borders that need consistent watering, the top half of the iris rhizome
should be left exposed so that it will not rot from being overwatered. Don’t plant
other perennials so close that they crowd the rhizomes and hold in moisture. And
don’t mulch. This will also lead to rots.
Iris rhizomes
The roots attached to the rhizome need to be covered with soil. Position the rhizome so
that the fan of leaves faces the direction in which you want the plant to grow. Allow 12
to 15 inches between each plant.
With the exception of reticulata iris, which have rounded, dark green leaves similar in
shape to chives, and Iris pallida ‘Variegata,’ which has green and
yellow striped leaves, all other irises have gray-green sword-like leaves. Iris leaves
form a wonderful, vertical accent to provide textural contrast to other rounded foliage in
the garden.
One thing is certain about irises. The gardener who plants them will have found a
proverbial pot of gold at the end of the rainbow!
Photographs, unless otherwise noted, courtesy of Judy Sedbrook.
