Landscaping With Irises

With careful selection, gardeners in a true temperate climate can have irises blooming for 11 months of the year. More often gardeners will fall in love with an iris - probably a bearded variety - and then find themselves seduced by a beautiful Siberian irises, or maybe a tall water-loving Japanese and decide to incorporate a variety of irises into their landscape.

In the border

If tall is what you need, irises offer lots of possibilities. Tall bearded irises, planted in a bed of their own, look superb in spring in full bloom. But when the flowers fade, the foliage alone looks rather sad and few gardeners today have the space to devote solely to one kind of plant. However, tall and intermediate bearded irises look great mixed with perennials. Group them in colors to create impact - a spotty scattering of single plants will not do them justice. Blend several shades of the same color or look for contrasts with flowers that bloom at the same time.  After the flowers have gone the leaves remain to make effective textural shapes among bushier plants.

There is a certain satisfaction about putting old varieties of different plants together, as if providing companions from a bygone era. The venerable I. pallida looks stunning beside crimson rugosa roses such as 'Roseraie de L'Hay', 'Scabrosa' or Rosa rugosa rubra. Another interesting way to grow old varieties of tall bearded irises is in a border backed by a hedge of stoechas lavender, which will flower for a long period in spring and again in summer if it is lightly trimmed after the first flush.

Even taller than the tall bearded irises, and flowering at a similar time, are the hybrid spuria irises. Their often strong color make them effective flowers for the back of the border or with a dark green hedge at their backs.

Siberians come in a range of heights. They are easy to grow, and as they bloom in early summer when roses are starting their first flush, these also fit well in a garden of perennials. Their attractive clumping form and tall slender flower stems add definition among fuzzier plants.

Suited to mass planting, they hold their own against weeds in an open area or along a winding walkway. They complement candelabra primulas, and they make an informal planting partnered with taller variegated grasses, a good background for summer perennials. Late-flowering sedums planted close by, such as Sedum spectabile 'Autumn Joy', would take attention away from the dying Siberian foliage in the fall.

Louisiana irises are another tall option, though recent breeding has produced plants of compact size that will fit into any garden scheme, large or small. They are adaptable plants, fitting into a perennial border, a bog garden or potted - in or out of water - as long as water is plentiful during the growing and blooming seasons. These irises are slow to come into bloom. The flower spike emerges from the foliage and may take three weeks before the bud finally opens. Stately iris branches, with their slim sheathed buds, add an element of expectation in a garden scene.

In bog or water

Water-loving irises can pose problems in mixed borders because of a thirsty habit which may not suit their neighbors. But they are beautiful creatures - in the "must-have" category. One solution is to create a bog garden where they can feel at home with other water-loving plants. Dig out an area of soil the desired shape to a depth of at least 12 in (30 cm). Line the depression with heavy-grade polyethylene and pierce it at intervals to provide drainage. Then refill the area with a slightly acidic, moisture-retentive soil mix -adding pine needles, peat or leaf mold will help -and keep it lower than the surrounding garden for ease of flooding. Rodgersias, hostas, filipendula and gunnera all like moist positions and provide a foil for narrow-leafed irises, whether their flowers be slender classic beauties or flamboyant floozies. Huge gunnera leaves are a wonderful counterpoint to flag irises in a stream area, and lady's mantle is another attractive companion plant, but it should be planted with its feet out of water.

In their country of origin, Japanese irises are planted in public gardens laced with zigzagging boardwalks. The beds are flooded in some areas so even the reflections of the blooms can be admired.

In containers

If you don't have a water feature, don't despair. Japanese irises grow successfully in containers and coordinating the pot to complement the flower color or garden furniture is part of the fun. Gardeners with a tiny garden and ample sun but no hint of water can enjoy Japanese irises this way. Place specimen clumps beside a bird bath or a seat where, even without flowers, the foliage will be attractive from spring to late fall. They will thrive with appropriate care, and they can be moved around to change landscaping effects -especially important in a small garden. Choose a large pot, provide lots of water from spring until late summer and feed the plant regularly until the buds form. Then stop, as too much food at this stage may make the buds falloff. Repot the plant after two years. In cold climates mulch it in winter or bury the pot in the garden.

Tall irises make a simple but effective focus where the emphasis is on hard landscaping. The boldness of sword-shaped foliage and shapely flower forms seem to be enhanced by the contrast of rocks, gravel and minimal planting.

As an accent plant for a courtyard grow Louisiana irises in a container. They like company, so choose a pot big enough to hold at least three and make sure the plants have plenty of water in spring and summer. Select a variety with dramatic flowers and while they are in bloom, move the pot to a prominent place. Once the flowers have died and the glamour has faded, shift the pot to an insignificant corner where it can be quietly left to its own devices until the following spring. At some stage before the next season, the irises will need to be removed from their pot, divided and repotted as they increase quickly.

While Siberian irises, tall bearded irises and spuria irises are not suited to container growing, most other irises will live in pots. It's an easy way to provide them with a growing medium to suit their individual needs. Whatever the iris, it will need regular fertilizing as they tend to be heavy feeders and will quickly exhaust any nutrients available in the potting mix.

In the rock garden

Tall irises hold their own in the hurly burly of border life, but small varieties can be quickly overpowered in similar conditions. For them, a rock garden is perfect. With the level raised, drainage is good; pockets can be filled with soil to suit the individual needs of a host of small plants, including irises. It's the ideal situation for early-flowering miniature dwarf bearded irises.

Plant I. cristata in front of dwarf bearded irises, preferably close to a pathway where passersby can admire the flowers, and place the taller I. graminea and Pacific Coast hybrids at the back where they can form spreading clumps.

Clumps of reticulata irises also enjoy a rock garden, with small hebes or dwarf rhododendrons in the background. Scabiosa, rock cress, dwarf phlox, alyssum and aubretia are companion plants to contribute color - just make sure they don't swamp the rhizomes of the bearded irises. Bulbous irises of the juno varieties, also suited to rock garden culture, will cope with groundcovers and come through mats of foliage.