Bring out the artist in you - plant Dutch Iris bulbs this autumn!

Dutch Iris Mixed - Picture courtesy HadecoDutch Iris Mixed - Picture courtesy HadecoDutch Irises are irresistible when in full bloom, but to enjoy their beauty in spring you need to plant them in autumn. The bulbs are available from the end of February, for planting out as soon as the soil temperatures drop. Find out how to grow and care for these bulbs below.

There’s no denying it, the blooms of Dutch irises are simply irresistible, and remain a  favourite of florists and gardeners, and it’s no wonder they captured the imagination of artists like Vincent van Gogh, who painted several pictures of them. Once you see a drift of Irises in full bloom, you’ll understand why it’s worth the effort to work a few into your landscape.

Iris is a genus of about 300 species of plants in the family Iridaceae, which includes some of the most popular and varied garden flowers. The diversity of the genus is centred in the northern temperate zones, occurring in a wide variety of terrains, and some of its most handsome species are native to the Mediterranean and central Asian areas.

Botanically, Dutch Irises are known as Iris hollandica or Iris x hollandica, and this group of Iris are actually hybrids of several different Irises. Some folks call Dutch Iris “Florist Iris,” because this is the type traditionally found in flower shops.

The story of the hybridization of the Dutch Iris is a long one, which began in 1564 when a specific Iris caught the eye of the Flemish doctor and pioneering botanist, Carolus Clusius, who was perhaps the most influential of all 16th-century scientific horticulturists. He was travelling through Spain when he saw the beautiful violet coloured Iris xiphium and was so enthralled by its beauty he sent bulbs back to Belgium, introducing what is now known as the “Spanish Iris” to the country.

Dutch Iris 'Dark Blue' - Picture courtesy HadecoDutch Iris 'Dark Blue' - Picture courtesy HadecoClick here to see google images of Iris xiphium

It was not until the end of the 19th century that the Spanish Iris was introduced to the Netherlands and Dutch growers eventually crossed it with Iris tingitana from north-western Africa. The resulting plant was a great success with larger and broader petals than its two parent plants, and became known as the “Dutch Iris”.

Click here to see google images of Iris tingitana

The name “Iris” was given to these plants for the variety of flower colours displayed, and the root of the word ‘iris’ stems from a Greek word for rainbow, and in Greek mythology Iris was the goddess of the rainbow. So it was the rainbow shades of Iris flowers that inspired the name, which is most apt for modern Dutch Irises, as they are renowned for their distinctive flowers and satiny petals in shades of blue, violet, yellow, rose, gold, and white, displaying six exquisite petals - three central, upright ‘standards’, and three larger outer ‘falls’ that recurve outward, and often have streaks of yellow or gold on the falls.  

The most popular colour is probably the blue iris, as blue is a rare flower colour in nature, followed by the purple ones. You can also find Dutch Irises in other hues, including rose, burgundy, bronze, burnt orange and other tone variations, but these are not freely available in South Africa.

Uses:

Dutch Irises are sought after cut flowers which can be found in florists almost all year round because professional flower growers use temperature manipulation to trick the bulbs into flowering out of season – a technique also used on lilies and tulips.

In the Garden:

Bring out the artist in you and plant some Dutch Irises this autumn. Today they are used in new and innovative ways, and the deep green, grass-like foliage compliments modern garden designs, where they combine beautifully with ornamental grasses and other low maintenance garden plants; and for a picture perfect display, combine them with other spring flowering bulbs and annuals.

The flowering stems can reach up to 80 or 90cm tall, allowing Irises to show off their blooms amongst other shorter flowers, and one of the reasons Dutch Irises are great in containers – on their own or mixed with other plants to create a living bouquet.

Dutch Irises are excellent cut flowers, lasting very long in a vase, and the beauty of these flowers is that they’ll continue to open up once cut, making for a lovely lengthy display of colour. Cut the flowering stems when the flower buds are peeking about halfway out of the green sheath - the bloom should be unfurled slightly at the tip. Cut the stems close to the ground, but take care not to cut into leaves. To prolong the cut flowers life even further, replace the water in the vase every second day.

Dutch Iris 'Symphony' - Picture courtesy HadecoDutch Iris 'Symphony' - Picture courtesy Hadeco

Cultivation/Propagation:

Dutch Irises will grow between 40 to 90cm tall and spread 15 to 20cm wide, growing in winter to flower in early spring, before going dormant again during summer. They grow best in cool to cold climates and will tolerate moderate frost and temperatures as low as 0°C. Dutch irises will also grow in subtropical regions, and are known to tolerate the heat and humidity in Florida and Texas, where they are treated as annuals. In warm winter climates like South Africa the bulbs will start producing foliage in late autumn or early winter but will only flower in spring.  In severely cold regions, you will not see any foliage growth until spring.

Wait until autumn when the soil temperature has dropped, before planting, usually anytime from mid-April to mid-June. Because Dutch Irises love a cooler climate and go dormant when the weather warms up, you can easily manipulate the plant to make it flower early in September by placing the bulbs in the fridge for six weeks before planting them. The advantage of doing this is, because they start flowering earlier, they will also flower for longer.

Although Irises require sunlight to flower, and in overseas catalogues they are mostly sold for full sun, in our hot climate avoid positions with full sun, and rather select a semi-shaded position in the garden, or a position which receives morning sun and afternoon shade. Never plant anywhere close to hot paving, or close to a hot north-facing wall. The overhanging branches of shrubs and deciduous trees will also help to protect the plants from too much sun.

Iris bulbs like a fertile, well-drained soil which has sufficient compost worked into it, and once the bulbs are planted, mulch or extra compost laid over the surface of the soil will go a long way in keeping the soil cool and moist. Never put anything, including fertiliser into the panting beds, or in the bottom of the planting holes, as direct contact with fertiliser can burn the bulbs, rather apply a light dressing with a granular organic fertiliser over the surface of the bed once you have finished planting, and water well afterwards.  Many gardeners prefer to start feeding with a liquid fertiliser only once the bulbs start growing.

Potted Dutch Irises need pots at least 20cm deep with drainage holes, and a good quality potting soil with excellent drainage will suffice. Remember that potted plants require more frequent watering than those growing in garden beds, as well as regular feeding with a liquid fertiliser throughout the growing season.

Usually the rule of thumb when planting bulbs is that they need at least 2 times their height of soil above them, but generally the planting instructions suggest you plant them about 5 to 10cm deep, and space them about 7cm apart, with the pointed end facing up. Remember to mark where you have planted the bulbs to avoid digging them up accidentally. If you are planting in pots, plant them closer together and place the pot in a cool, semi-shaded spot.

Water the pots or beds thoroughly after planting, soaking the soil to settle it around the bulbs, but try not to water again until the foliage emerges, however, if watering can’t be avoided at this stage it is not a problem, as long as the soil has perfect drainage. When the bulbs are actively growing and flowering, water deeply about once a week, but once flowering is over and the leaves start to die down, stop watering.

Dutch Iris 'White' - Picture courtesy HadecoDutch Iris 'White' - Picture courtesy HadecoIn colder climates, the bulbs can be left in the soil to naturalise, or they can be lifted and stored when the foliage has died down in summer. In South Africa this would be around November, but unfortunately, because we generally have a short and hot spring season, the bulbs don’t perform as well if they are lifted and stored for next season. For this reason they are usually treated as annuals and bulbs are purchased fresh each season. If you live in a cooler region and wish to try storing the bulbs, lift and store them at room temperature until early autumn and then transfer them to the refrigerator until planting time. If your soil drains well, you can just leave the bulbs in the soil and hopefully they will flower again next year.

Problems, Pests & Diseases:

If Dutch irises are grown correctly they will suffer from no serious pests or diseases, but as the weather warms up in spring, watch out for aphids and thrips and spay accordingly. Snails and slugs also become active at this time and may need to be controlled. Simply applying a layer of sharp grit on the soil around the plants will help to discourage this garden pest.

Warning:

Take care and use gloves when planting Iris bulbs as they can cause skin irritation.

Irises should not be eaten and are poisonous for dogs and cats.