The Perennial Matchmaker

Among the most well-known irises are the Bearded Hybrids, derived from German iris or common flag (Iris germanica). They’re available in a rainbow of flower colors and a wide range of heights—from Miniature Dwarf Bearded, to 8 inches in bloom, up to Tall Bearded types, which can reach 3 to 4 feet in bloom—with big, bold blooms that include a fuzzy center strip (the beard) on each lower petal. Bearded irises are usually hardy in Zones 3 to 10. Sweet or Dalmatian iris (I. pallida), for Zones 4 to 8 or 9, has a similar flower form but only in a purple-blue color; it blooms on stems 2 to 3 feet tall.

Siberian iris (I. sibirica) and its hybrids, for Zones 4 to 9, usually reach 2 to 3 feet in foliage and flower. Shades of blue to purple, yellow, and white are the most common flower colors. Their green leaves are long and slender: more grasslike than those of the bearded and sweet irises. Their flowers tend to look a bit more refined, too.

Japanese iris (I. ensata, also sold as I. kaempferi) blooms a bit later than the Siberians, with large, broad flowers in shades of blue, purple, pink, and white on 2- to 4-foot stems. Japanese iris is recommended for Zones 4 to 9.

Oh, the endless possibilities for making glorious color combinations with irises! While some flower in a single, solid hue, most include at least one other color: darker or lighter veining or edging, for instance, or white and/or yellow toward the center, or different-colored petals in the same bloom. Choosing companions that repeat these secondary colors is an easy way to make eye-catching pairings. Below are some other ideas to keep in mind when working with irises in color combinations.

Based on blues. As with lots of other “blue” flowers, irises tend to be more on the purple-blue side, with an infinite range of lighter tints and darker shades. Many are blue enough to satisfy folks who appreciate that hue, though, and their bloom times overlap with many other beautiful flowers in the same color range, so late spring to early summer is an ideal time to indulge in blue-based combinations or an entire blue border.

Blues can be hard to see from a distance, especially if they’re against a dark fence or deep green shrubs, so it’s a good idea to keep them near your house or along a walkway, where you can admire them up close. Consider adding a touch of white, too, in the form of white flowers or white-variegated or bright silver leaves, for a bit of variety. Tucking in just a few yellow flowers and chartreuse or yellow-variegated foliage partners among the blues can serve the same purpose.

Working with white. Irises offer some of the most pristine whites you can find in the world of flowers, making them invaluable for visual impact in white-based groupings and gardens. Besides white flowers, consider partners with white-variegated, silvery, gray, or blue foliage. A planting like this would look particularly striking in a lightly shaded spot or against a dark-colored background.

Pretty in pastels. There are so many options here—from near-whites with just the slightest touch of color to pale pinks, peachy oranges, buttery yellows, baby blues, and soft lavenders—and they all look lovely together. Pastel color schemes work particularly well with the mid- to late-spring-flowering irises, because their delicate tints tend to hold up best when the weather is still cool and the sun isn’t too strong. When you’re putting together a perennial border based on pale pastel colors, think about including some irises or companions with slightly richer shades (such as a few medium pinks, yellows, or lavenders), and perhaps some purple foliage, to add a little intensity to the scene.

Think pink. A whole bed or border based on pink? Definitely! It’s almost too easy with the many tints and shades available among bearded irises and the other pale pink to magenta perennials that bloom around the same time, such as hardy geraniums (Geranium) and peonies. Keep the look light with silver- and gray-leaved companions or add intensity with some dark-foliage partners, such as Fine Wine weigela (Weigela florida ‘Bramwell’).

Other companionable colors. Yellows are most often associated with late-summer gardens, but you can enjoy the same sunny cheerfulness earlier in the growing season with the pale to intense yellows available in the bearded and Siberian irises. Combine them with other yellows and white; with warm reds and oranges; or with pastel blues and pinks. If you prefer things more on the moody side, check out some of the practically black bearded irises, such as ‘Before the Storm’ and ‘Superstition’. Match them with equally dark partners, such as black mondo grass (Ophiopogon planiscapus ‘Nigrescens’) and ‘Obsidian’ heuchera (Heuchera), or contrast them with silver foliage and white flowers.

Look to the leaves. Some irises offer intriguing foliage colors that you can use to repeat or harmonize with the primary or secondary colors of blooming companions. Many bearded irises have a blue or gray cast to their leaves, particularly in spring to midsummer, and sweet iris foliage is especially good as a blue-green accent among green and silver leaves or pastel flowers. Sweet iris also offers two outstanding foliage selections: variegated sweet iris (I. pallida ‘Variegata’), with creamy yellow and blue-green striping, and ‘Argentea Variegata’ sweet iris, with ivory white and blue-green striping. Variegated Japanese iris (I. ensata ‘Variegata’) also has vividly white-striped leaves.

A Perfect Match

One of my all-time favorite irises is ‘Gerald Darby’. It’s a selection of Iris × robusta, which is a hybrid of two North American species: I. versicolor and I. virginica. Its graceful, purple-blue flowers are charming, and the dark stems are interesting, too, but its best feature is the rich purple blush on the young leaves. The color is usually gone by early summer, but through spring, the showy foliage makes a fantastic partner for early bloomers, such as white ‘Thalia’ daffodils.

The blooms of most irises tend to be on the big and bold side, holding their own with other in-your-face flowers, such as those of giant onion (Allium giganteum) and peonies. For contrast, combine them with partners that have small, airy, or spiky blooms, such as catmints (Nepeta).

The leaves of irises may be slender and grasslike or wider and swordlike—ideal for repeating the shapes and textures of ornamental grasses and other spiky plants, such as daylilies (Hemerocallis), phormiums (Phormium), and yuccas (Yucca). For contrast, consider bedmates with foliage that is broad, like that of hostas; rounded to oblong, like that of upright sedums (Sedum); fine, like that of perennial candytuft (Iberis sempervirens); or ferny, like that of astilbes (Astilbe). Perennials with rounded to mounded forms, like hostas and peonies, are also very useful for adding contrast to irises.

Get a jump on the iris season by pairing some of the Miniature Dwarf Bearded and Standard Dwarf Bearded hybrids with other spring bulbs and perennials and with low-growing groundcovers, such as creeping sedums, which will help to keep spring rains from splashing mud onto the beautiful iris blooms. Late spring to early summer is prime iris time for most areas (make that early into late spring for those of you in the South), followed by Japanese iris into midsummer.

“Reblooming” bearded irises, such as white ‘Immortality’, blue-and-white ‘Clarence’, pink ‘Pink Attraction’, and bright yellow ‘Pure as Gold’, may surprise you with fresh flowers in late summer and fall, especially if the soil is relatively fertile and rainfall has been regular.

Variegated irises remain showy well into autumn, and Siberian iris leaves turn shades of yellow as temperatures cool, looking lovely with rich pink and purple asters and other fall-colored perennials and shrubs.

While irises can fit into pretty much any site or garden style, there are a few places where they’re particularly worth considering.

Cottage gardens. It’s hard to imagine the blowsy beauty of a classic cottage-style planting without at least a few irises—especially the Bearded Hybrids and Siberians. Complete the theme with other traditional cottage-garden perennials, including dianthus (Dianthus), lady’s mantle (Alchemilla mollis), lupines (Lupinus), peonies, and perennial salvias (Salvia).

Rain gardens. Slightly sunken and planted with tough perennials, rain gardens are designed to capture water from gutter downspouts, giving it a chance to soak in and rejoin the natural groundwater instead of running off into the sewer system. Rain-garden plants need to be able to tolerate dry periods as well as occasionally saturated soil. Japanese irises are well suited to the lowest parts of these gardens, where the soil tends to stay moist the longest, while Siberians can work well closer to the edge. Hardy hibiscus (Hibiscus), Joe-Pye weeds (Eupatorium), perennial lobelias (Lobelia), and cinnamon and royal ferns (Osmunda cinnamomea and O. regalis) are just a few compatible companions for irises in rain gardens.

Spread the Wealth

Most irises bloom for only a few weeks, and the start and duration of the flowering period for any given iris can vary by a week or more from year to year, depending on the weather conditions. That means that it’s possible for an iris and its companion to perfectly complement each other one year and miss each other completely the next.

To increase your chances of enjoying a splendid show, include more than one iris cultivar in a bed or border, if you have the space. Instead of three ‘White Swirl’ Siberian iris (Iris sibirica), for instance, consider one ‘White Swirl’, one ‘Fourfold White’, and one ‘Gull’s Wing’. Take full advantage of partners with colored foliage in your iris bloom combinations, too, so you’ll be guaranteed some pretty pairings even if the various flower-based groupings don’t exactly coincide.

Bloom Buddies

Marvelous Matches for Flowering Combos

Here’s a sampling of suggested companions for each of the most common kinds of irises, based on their bloom times and growing conditions.

Partners for Bearded Hybrids or sweet iris (Iris pallida) in full sun and average to dry soil:

Baptisias (Baptisia)

Catmints (Nepeta)

Dianthus (Dianthus)

Euphorbias (Euphorbia)

Mulleins (Verbascum)

Oriental poppy

(Papaver orientale)

Partners for Bearded Hybrids, sweet iris, or Siberian irises (I. sibirica) in full sun to light shade and average to somewhat moist, well-drained soil:

Bellflowers (Campanula)

Bluestars (Amsonia)

Columbines (Aquilegia)

Delphiniums (Delphinium)

Foxgloves (Digitalis)

Hardy geraniums (Geranium)

Lady’s mantle (Alchemilla mollis)

Lupines (Lupinus)

Peonies (Paeonia)

Perennial salvias (Salvia)

Speedwells (Veronica)

Partners for Japanese iris (I. ensata) in full sun to light shade and moist but well-drained soil:

Astilbes (Astilbe)

Bee balms (Monarda)

Daylilies (Hemerocallis)

Globeflowers (Trollius)

Shasta daisy (Leucanthemum × superbum)

Swamp milkweed (Asclepias incarnata)

Exploring More Options: Partners beyond Perennials

Shrubs and vines can be very useful as background plants for medium-height to tall irises. Some that usually flower during peak iris season include hybrid clematis (Clematis), lilacs (Syringa), roses, rhododendrons (Rhododendron), and viburnums (Viburnum). Take advantage of those with colorful foliage, too, to harmonize or contrast with your irises. A few that look particularly pleasing with irises include yellow-leaved spireas (Spiraea) and dark-leaved elderberries (Sambucus nigra) and weigelas (Weigela).