Dietes : Pretty Tough Plants

Indigenous wild irises are the perfect plants for the busy gardener as they are low maintenance, water wise and easy-to-grow plants.

Wild iris, or butterfly plant, as it is also called, is a delight to grow. It is a tough plant that will grow in most soils and, once established, will survive harsh growing conditions – even tolerating drought. Conversely, wild iris (Dietes spp.) will also grow in boggy gardens. It can be grown in full sun or semi-shade and is usually pest- and disease-free.

There are five indigenous species of wild iris – Dietes bicolor, D. butcheriana, D. flavida, D. grandiflora and D. iridioides. All these species, but especially the yellow wild iris (D. bicolor) and the large wild iris (D. grandiflora), make attractive garden and landscape plants. The blooms of the latter two are borne on top of long flower stalks above 90cm-tall foliage. Their leaves are evergreen and grass-like, and the plants grow to form attractive clumps.

Dietes are sensitive to long periods of frost, with the exception of D. grandiflora and some D. iridioides varieties that can withstand moderate frost as long as it is not for an extended period of time. Although tolerant of a variety of growing conditions, dietes perform best when planted in well-composted, slightly acid soil and need regular watering in summer.

Garden favourites

• Dietes grandiflora: The large wild iris bears spectacular large white flowers marked with yellow and violet in spring and summer. It grows in both sun or partial shade, and is also tolerant of both moderate frost and drought. It will also grow well in coastal gardens in a partially shaded position that is protected from the wind. For best results in inland gardens, plant in full sun and keep well watered during the summer months.
• Dietes bicolor: The yellow iris has slightly smaller pale yellow blooms marked with brown which are borne in spring and summer. Although in the wild the yellow iris occurs naturally near streams, it is also drought resistant. In addition, it is fast growing, easy to grow, and tolerant of mild frost. It grows best in full sun except in hot inland gardens where partial shade is best.
• Dietes iridioides: With a height of 50cm the wood iris makes an excellent ground cover in difficult parts of the garden – it spreads rapidly to cover the ground. The flowers are similar to those of D. grandiflora, but smaller, and the leaves are wider, resembling those of bearded iris. It will grow in sun and partial shade. The wood iris does not tolerate frost, but some cultivars, such as the newly released variegated D. iridioides ‘Silver Sword’, can withstand sub-zero temperatures, provided they are not a regular occurrence.

Landscaping with wild iris

Wild iris can be used in the garden in many ways.

• Mass planted. This method is both practical and pretty: practical, because wild irises are evergreen, low water usage plants, and pretty because the massed blooms are enchanting during the long flowering season.
• As a ground cover. There is no rule that says ground covers have to be low growing plants. In a large water wise garden with different water usage zones, massed wild iris is ideal as a ground cover for the low water usage zone.
• Under trees. Although wild iris does not flower well in shady conditions, this plant is nevertheless one of the few that can satisfactorily grow under trees in spite of tree root competition for water and nutrients. Give it a good start with plenty of compost and regular watering.
• As accent plants. Individual plants can be used as accents in mixed borders, or in pairs elsewhere, such as at either side of a bench, the entrance of a pathway or at the top of a flight of steps.
• On slopes. Because of their spreading rhizomatous root systems, and because they are fast growing, wild irises can be included in slope plantings, and make attractive focal points amongst low-growing plantings with contrasting foliage, for example, succulent foliage.
• In containers. Wild iris will give the same contemporary ambience as grasses planted in containers. Just make sure you choose a large container.

Tips for success

For a profusion of blooms plant wild iris as follows:

• Grow in a position that receives full sun or partial shad
• Although tolerant of tough conditions, dietes will perform best in well-drained soil, rich in organic material.
• Fertilise in spring with a balanced general fertiliser.
• Water twice a month during dry spells.
• Do not remove flower stems as they continue to flower for several years.
• Propagate by division of the established clump in early spring, just before active growth begins. Seeds are sown in spring but can take many years to germinate.