Irises from the iris family (Iridaceae) belong to the most diverse herbaceous plants for the garden. Botanically, the genus is named after Iris, the Greek goddess of the rainbow – a suitable patron saint in view of the wide range of flower colours. The spectrum is huge, from small, fine-wheeled variants of the dwarf iris to the brilliant flowers of the higher-growing bearded iris (Iris barbata).
More than 200 species can be found in nature, most of them growing in the temperate zone of the northern hemisphere. Breeders are particularly attracted by the group of Bart-iris with their numerous crosses and varieties. White, yellow, orange, blue, pink, red and even nearly black as well as multicolored forms, in addition different growth heights of about 15 to 110 centimeters, leave nothing to be desired. Varieties of the meadow iris (Iris sibirica), the steppe iris (Iris spuria) and the dainty net leaf iris (Iris reticulata) form other important groups and complete the assortment with a whole range of botanical species.
Appearance and growth
The three-part flowers appear graceful in some irises and opulent in many. The early species flower as early as February, most varieties from April, and later show their flowers in July. Some species, such as the meadow iris and the swamp iris, produce conspicuous cylindrical capsule fruits. Characteristic for all mentioned species are the narrow, sword-like leaves, which sometimes remind a little of grasses. As storage organs, irises have rhizomes or tubers, while the early-flowering net leaf iris forms small bulbs and is usually offered together with other bulb flowers such as crocus or narcissus.
Location and soil
Most species of irises thrive in sunny places with nutrient-rich soil. It is important to have a well-ventilated soil that is not too acidic. Bart-iris tolerate dryness and can therefore be combined with other species such as thyme and stonecrop at appropriate locations. Basically, this iris likes a loamy, but permeable soil in a warm, sunny place best. The same applies to the steppe iris (Iris spuria), a sun worshipper who does not tolerate wetness. The small net leaf iris (Iris reticulata) and some of its relatives are ideal for the rock garden, where they show their flowers early in the year. The dwarves can also be cultivated well in pots, but you have to protect the pots from too much moisture, especially in winter. On the other hand, the meadow iris (Iris sibirica) thrives in fresh, i.e. more humid locations, while the swamp iris (Iris pseudacorus) even prefers the wet edge of the pond.
The rhizomes of the irises are flat in the ground, so that the upper third still looks out of the ground. To make loamy soils permeable, loosen the soil and add sand. In addition, the rhizomes can also be laid on a layer of sand as thick as a thumb. The ideal planting season is from August to mid-October, when the plants can still take root. However, planting in November and spring planting in March are also possible. Potted goods can be planted all year round – except in winter. If you want to replant beds, you need five to seven plants of the high varieties (Iris barbata-elatior) for one square metre, and 12 to 16 plants for low Barbata-Nana varieties.
If the inflorescence is wilted, it should be pruned back at the base of the leaf so that the perennial does not put any unnecessary force into the seed formation. A number of iris varieties can even be inspired to flower a second time in autumn through consistent pruning, such as the white-apricot ‘Champagne Elegance’ or the violet ‘Lovely Again’. Fertilizer is used for budding in spring, a potassium fertiliser is optimal. But even mature compost can satisfy the nutrient requirements of the irises.
If the blossom is dying after a few years, you should divide large pieces of rhizome with a sharp knife. To do this, take the rhizome out of the ground with a digging fork and place the cut at the points recognizable as constrictions. Each cut should have a well-developed leaf head and roots. The edge pieces are the most vital. After dividing the rhizomes, the leaves are shortened by about half. This reduces evaporation until the plants are well rooted again. The best time for this is late summer. The procedure is recommended every three to four years, especially for large-flowered varieties, because otherwise they will age, become bald from the inside and lose their bloom.
Wintering or winter protection
Many species of irises are hardy and can easily spend the winter outdoors. Species for damp to wet soils such as Iris sibirica are loosely covered with leaves and straw throughout the winter. Irises in pots should be placed in the shade of rain in winter, e.g. under eaves on the house wall. Otherwise there is a risk of root rot in wet conditions.
The possible uses of irises range from the herbaceous border to the edge of the pond to the rock garden or planting in a pot. With its bright flower colours, the bearded iris is a magnificent perennial in the best sense of the word and ennobles every perennial bed. Classic partners are peony, larkspur, daylily and poppy. Low beard irises decorate the spring terrace as soloists in clay pots, while planting partners such as dwarf blue fescue and tulips skilfully set the scene in the bed. The Hohe Bart-Iris works wonderfully together with lavender, ornamental garlic or giant feather grass.
Due to the unbelievable variety of irises, they have been divided into groups: Depending on their size, they are referred to as Low Bart-Iris (Iris barbata-nana, 15 to 40 centimeters), Medium Bart-Iris (Iris barbata-media, 40 to 70 centimeters) and High Bart-Iris (Iris barbata-elatior, 70 to 120 centimeters). The lower the dwarf iris, the earlier the flowering usually begins: low beard irises start flowering in April, the larger varieties in May and the 5 to 15 centimeter small dwarf iris in spring. The flowers of the bulb flowers appear delicate and delicate in bright blue and lilac shades. These include the varieties of the reticulated iris (Iris reticulata) and the small dwarf iris (Iris histrioides). From April, the dwarf beard iris opens its buds. The Hohe Bart-Iris and its varieties bloom in late spring and early summer. The enormous variety and the fascinating flowers make the heart of every hobby gardener beat faster. These perennials, mostly over a metre high, flower from May to June. Wild species such as steppe iris (Iris Spuria hybrid) and pale iris (Iris pallida) are especially popular with lovers.
Among the breeding successes are Bart-iris, which bloom a second time in autumn: the so-called “Rebloomers” go through two flowering cycles a year. A reliable variety is, for example, Iris barbata-elatior ‘English Cottage’ with white flowers, streaked with delicate purple veins.
In principle, the reproduction of irises by seeds is possible, but the division of the rhizomes is the simpler and quicker way (see “Care tips”). Here the descendants are also surely varietal.
Diseases and pests
Unfortunately, snails also do not stop at irises, however, the infestation pressure is not so high on the locations preferred by most species: they are simply too dry. The onions of net leaf iris and other onion iris are often eaten by voles. In principle, however, the perennials are not susceptible to plant diseases.
Irises in the our store-Shop
I am Don Burke, one of the authors at My Garden Guide. I am a horticulturist that cultivates, grows, and cares for plants, ranging from shrubs and fruits to flowers. I do it in my own garden and in my nursery. I show you how to take care of your garden and how to perform garden landscaping in an easy way, step by step.I am originally from Sydney and I wrote in local magazines. Later on, I have decided, more than two decades ago, to create my own blog. My area of specialization is related to orchid care, succulent care, and the study of the substrate and the soil. Therefore, you will see many articles dedicated to these disciplines. I also provide advice about how to improve the landscape design of your garden.