Irises by Van Gogh

Irises by Van Gogh

I’ve thought for some time that I must grow more Irises in my garden, but somehow the massive choice and being not quite sure about how to grow them successfully tends to make me wary.
I have grown some bearded irises in pots (and they’ve done quite well, despite a bout of Iris Rust last summer), and also some bulbous varieties in the border – they always please, as much for their strappy green foliage as for their flowers. I must be a bit more adventurous and devote a largish area to a bold display of one or two varieties – when I can afford it!

Iris persica - a bulbous Iris as drawn by Sowerby in 1792

Iris persica – a bulbous Iris as drawn by Sowerby in 1792

Irises – otherwise known as Flags, Sword Lilies or Fleur de Lis – is a genus of some 300 species from very varied habitats from around the northern hemisphere. They vary between those that are bulbs, those with rhizomatous (expanding, tuberous) roots, and some that are fleshy – rooted. They can be evergreen or deciduous and have very varied growth requirements. Irises are classified by the Royal Horticultural Society into these sub sections or ‘subgenera’:

  • Bearded species and cultivars– various sizes from miniature dwarf to tall. These are the most widely grown group of Irises, are rhizomatous and prefer well drained soil.
  • Aril irises are a group of bearded irises that become dormant in the summer after flowering and need to be kept dry whilst in this state.
  • Beardless irises generally have more flowers per stem, than  bearded types. They are also rhizomatous and prefer well drained conditions, apart from the Laevigate group which needs damp soil.
  • Crested irises are rhizomatous, spread freely, and prefer moist soil.
  • Bulbous irises are beardless and summer dormant. They prefer well-drained soil.
Iris aphylla -with prominent 'beard'

Iris aphylla -with prominent ‘beard’

Iris orientalis showing rhizome roots

Iris orientalis showing rhizome roots

The Iris has connections with ancient Greece, where Iris was the messenger of the Gods, communicating between heaven and earth through a rainbow (so a reference to the wide range of Iris colours available). Irises have been valued plants for a long time and the flowers have had a long association with heraldry and royalty.

The iris flower has three outer and three inner tepals (a uniform type of petal on the outer part of the flower). The outer three bend back and may also hang down, so are referred to as ‘falls’ – they are usually the most colourful part of the flower and are especially large and colourful in the bearded irises, which have white or coloured hairs, like a beard, in the centre of each fall. Crested irises have a ridge (or crest) on each fall.

The three inner tepals are called ‘standards’, as they generally stand upright in the middle of the flower (like a flag), but may also lie horizontally as in I. tectorum; droop as in I. bucharicha; or be much reduced as in I. danfordiae.

Three modified styles called stigma flaps reach out over the falls from the middle of the flower and can be an important feature. The iris flower is of interest as an example of the relation between flowering plants and pollinating insects, the shape of the flower and the position of the pollen-receiving and stigmatic surfaces on the outer petals forming a convenient landing-stage for flying insects. All parts of the Iris plant are poisonous and contact with the sap may cause skin irritation. However, Irises are low in allergens.

Iris orientalis

Iris orientalis

Iris 'Samurai Warrior'- the closest breeders have come to a red Iris

Iris ‘Samurai Warrior’- the closest breeders have come to a red Iris

Irises are extensively grown as ornamental plants in home and botanical gardens. They grow in any good free garden soil, the smaller and more delicate species needing only the aid of turf ingredients, either peat or loam, to keep it light and open in texture. The earliest to bloom are species like I. junonia and I.reichenbachii, which flower as early as February and March (Northern Hemisphere). These are followed by the dwarf forms of I. pumila which blossom in Spring, and these are followed in early Summer by most of the tall bearded varieties, such as the German Iris and its variety florentina, Sweet Iris, Hungarian Iris, Lemon-yellow Iris and their natural and horticultural hybrids such as those described under names like I. neglecta or I. squalens.

 

The Iris is hardy, reliable, and easy to grow. Irises also attract butterflies and make lovely cut flowers. The Old Farmers’ Almanac suggests the following tips for growing Irises:

  • ‘Irises need at least half a day of sun and well-drained soil. Without enough sun, they won’t bloom.
  • They prefer fertile, neutral to slightly acidic soil. If your soil is very acidic, sweeten it with a bit of lime, and forbear summer watering, which can lead to rot.
  • Bearded irises must not be shaded by other plants; many do best in a special bed on their own.
  • Soil drainage is very important. Loosen the soil with a tiller or garden fork to a depth of 12 to 15 inches, then mix in a 2 to 4-inch layer of compost.
  • Plant iris in mid to late summer.
  • Bearded irises have rhizomes (fleshy roots) that should be partially exposed, or thinly covered with soil in hot climates.
  • Plant rhizomes singly or in groups of three with the fans outermost, 1 to 2 feet apart, depending on the size.
  • Dig a shallow hole 10 inches in diameter and 4 inches deep. Make a ridge of soil down the middle and place the rhizome on the ridge, spreading roots down both sides. Fill the hole with soil and firm it gently.
  • Water thoroughly.
  • When planting, top-dress with a low-nitrogen fertilizer, and again in early spring.’

As I conclude this article, I’m already thinking of an open, sunny spot where a bold display of summer flowering bearded Irises (one of the brown ones like ‘Kent Pride’) would look great in Old School Garden. Perhaps mixed in with some purple Heuchera to mask their rhizomes and some later seasonal interest ….watch this space.

 

PicPost: Bearded Beauty

Bearded Iris drawn by Sue Walker White

Further information:

Pictures of Iris varieties

About Iris

British Iris Society

National collection of water irises event

Iris weekend 6-7 July, Rosemoor, Devon

Places to see Bearded Irises in May- June:

Godlington House, Kent

Marks Hall Garden & Arboretum, Essex

Doddington Hall, Lincolnshire

Old School Gardener

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