Iris have managed to equally capture the imaginations of artists, authors, poets and garden lovers on a global scale. The large variety available make Irises adaptable to suit different garden and pond planting situations.
Iris originate primarily from the northern hemisphere from Europe, Asia and into North America. Apart from the many hundreds of hybrid cultivars of bearded and Louisiana iris bred for their colour patterning and size, irises are still one of the very few flowering plant species grown for their individual species in home gardens.
Bearded Iris (Iris germanica)
For most gardeners in cooler temperate regions, the tall or dwarf bearded iris are often the plants of choice for garden additions. They are relatively easy to incorporate in amongst other perennials and don’t take up too much space in smaller gardens. Their amazing flowers are unmissable when in bloom with an almost “royal” accent; they are available in a never-ending array of colours that will suit everyone’s taste from purest of white to the deepest of violet/black with the exception of strong red. The gentle, yet bold structure of these irises will truly stop you in your tracks as you become almost mesmerised by the intricate patterning, “stitching” and veining of colours on the flowers lower (pendulous) petals often referred to as “falls”. Some of the older forms can be successfully grown in warmer parts of the country, but all will flower better and stronger if given some winter cold.
Flowering time: (Depending on cultivar) mid-spring until late summer
Louisiana Iris (water Iris)
One iris species that easily spans all climates is the dependable Louisiana iris group. As the name implies, this species originates in North America and can handle both cooler climes and hot, humid conditions. Louisiana irises are essentially a bog iris and will revel in wet or heavy soil and equally at the edge of ponds. Their foliage is deep green in colour and when in flower can reach heights of over a metre. For those without a pond or boggy ground, they can easily be grown in large tubs or shallow water features, yet will require splitting every second year. Louisiana irises are fast growing and require a full sun position to flower at their best and like the bearded iris, are available in a rainbow of colour tones to suit every taste.
Flowering time: (depending on cultivar) early spring until mid-summer
Iris virginica (Blue Flag iris)
Like its cousin the Louisiana Iris, Iris virginica also hails from North America and is happiest in boggy, wet soil and can also be successfully grown at water’s edge. This iris differs from the Louisiana form in that is it more slender in its flowering, foliage is pendulous and grows in a gentle circular arch shape and flower colour is restricted to pastel shades of lavender, lilac, blue and white. Although a strong species, it detests heavy competition from other iris and should be grown on its own to enjoy its quiet elegance. Iris virginica can also be successfully grown in partly shaded sites in the garden.
Flowering time: mid spring to late spring
Iris sibirica (Siberian Iris, Siberian flag)
If strong structure is something you are looking for in a plant, then the Siberian iris simply cannot go unnoticed. Enjoying cooler temperatures for best growth and flowering, this true European species will simply take your breath away when in bloom. This species is a rhizomatous herbaceous perennial which grows up to an average 1.3 metres tall, with narrow grassy foliage and branched stems that produce up to five blooms per stem that open successively over a long period. It enjoys a well-drained, yet moisture retentive soil in full or part sun. It is native to Europe and Central Asia and is one species that looks incredible if mass planted in amongst small grasses or moisture-loving wildflowers.
Flowering time: early to mid-summer.
Iris Pseudocorus (Yellow Flag Iris)
A true water loving species, the Pseudocorus iris is one of the unsung heroes of the iris world.
Originating from Britain, Europe and parts of North Africa, this tall, evergreen species makes a dramatic addition to any garden that carries the advantage of space. It is best grown around large dams or water features where its brilliance can be available for all to see. The elegance of the Yellow flag iris is unmistakable as it produces multiple bright golden flowers along each upright branch from late September and can often continue until Christmas. This is a thickly clumping iris that supports an incredible habitat for many of our native frog species where they can breed and lay eggs in amongst the foliage at water level. The variegated foliage form is a real head turner with its vividly striped cream and green foliage yet is rarely on offer. A full sun to lightly shaded position suits it best.
Flowering time: early spring until early summer
Iris Tectorum (Japanese roof iris)
The Japanese roof iris is one of the best iris species for anyone entering the world of the iris. This small iris to fifty centimetres is a perfect choice for garden borders or edging in smaller gardens and is often confused as a dwarf bearded iris in its flower shape. It is an old fashioned form that will easily grow in both sub-tropical and temperate climates and prefers a shallow, yet nutritious soil. Unlike other iris, this species begins its flowering from mid-winter and continues until early spring in warmer zones, and early spring until mid-spring in cooler climates. Iris tectorum is mainly seen in shades of mauve and lilac, yet there is also a rare white form that is slower to grow. It is the largest flowering member of the ‘Evansia’ Iris group
Iris japonica & Iris Cristata Iris Evansia group: (Crested iris, Woodland iris)
For those with semi-shaded or shaded gardens with large trees, then the I. japonica or I. cristata or crested iris could be the choice for you. The crested iris group are generally a fast growing, small species to just over fifty centimetres in height and will smother the ground with many fans of lush green foliage for most of the year, when in spring, erupts dainty sprays of fairy-like crystal white blooms that if you look closer, will be intricately patterned with lines of violet splashed with gold. There are also gentle lavender coloured forms available. This is a quick multiplying species that can be very useful in filling in those spaces under trees and successfully combined with the likes of clivia, begonia and many woodland bulb species. Its tolerance of drier conditions makes it increasingly useful in water conservation with some species producing a gentle fragrance.
Flowering time: mid to late spring
Iris ensata (Japanese water Iris)
As suggested, this species hails from Japan yet can also be found in Korea, China and Russia and although generally of a more demure nature in stature, makes up for this with its flamboyant large, silken blooms that are intricately veined along the broad petals. Ranging in colours from white through purple and all tones in between, this water iris is well suited to smaller gardens and is an artist’s dream with its graceful stance as it seems to extend its outer petals at an almost horizontal angle towards its many admirers.
Flowering time: mid spring until early summer
Nutrition in the form of manures or 5 IN 1 Organic Plant Food along with (granulated) sulphate of potash should be added to the soil prior to planting many of the soil dwelling species. Occasional seasonal top ups of a slow release fertiliser such as Robust Controlled Release Fertiliser while at the beginning of the growth cycle and end of flowering will greatly assist to build the size of the clumps for division and propagation the following season. Avoid fertilisers that are excessively high in nitrogen as this will only stimulate foliage growth at the expense of flowers.
For water loving species, look for specially prepared (aquatic) slow release tablets that you can submerge into the surrounding soil or pots to help sustain good growth, yet not be too high in nitrogen to evoke an algae breakout.
Unless breeding for new colour variants, the best time to prune any iris is to remove all spent flower heads as soon as each spike has finished. This will save energy of the plant and can often encourage a few extra flush of flowers for their individual season.
Propagation of most iris species should be done while plants are either just beginning their dormancy or in the case of evergreen species, during late autumn into winter. All foliage should be pruned back to a small (upward pointed) fan shape to conserve energy and allow the plants to push forth their new foliage. Young plants should be potted up immediately or soon after splitting. Removal of any old or diseased root systems is strongly suggested.
Bearded Iris (once divided and trimmed) can be stored bare-rooted in a cool position and “healed” into slightly moistened wood shavings or coir peat for planting within thirty days. Once planted out, apply SeaMax Liquid Seaweed at half strength until a full crown of new growth can be seen then monthly applications will keep the plants growing vigorously.
Iris in the garden:
They are best, first planted in bold (species) groupings of six to nine of the same colour, so as to bring out their best attributes and create a dramatic effect when in bloom.
As some are rather tall by nature, they work well if planted from the middle to the rear of garden beds to form backdrops for smaller plants.
Some, like the bearded iris group, prefer to be planted in full sun in very well-drained soil with their rhizomes allowed to be “baked” in the sun, while many others, such as the louisiana group, enjoy wet soils and often can be seen revelling alongside water’s edge of ponds or dams. For some of the bulbous species such as Dutch Iris, they prefer a free draining, slightly gritty, yet average soil and look very much at home amongst rock gardens and even amongst some succulents.
All rhizomatous forms have early, mid and late flowering cultivars, so clever selections in each category will guarantee successive flowering from mid-September right through until January providing a continual flowering display.
Although most Iris are not overly concerned with soil pH, the dwarf and tall bearded iris are naturally adapted to slightly chalky soils and do enjoy some added calcium in the way of dolomite.