One of the most treasured irises out there is a bulbous hybrid iris from the subgenus Xiphium called Iris × Hollandica (EYE-ris hol-LAN-dee-kuh).
The plant was hybridized from 2 varieties of Iris xiphium and Iris tingitana in the 1800s by the Dutch company van Tubergen and has become one of the most popular specimens for florists.
I. Appearance and Characteristics
Iris × hollandica, commonly known as the Dutch iris, is a hybrid iris developed from species native to Portugal, Spain and North Africa (Iris tingitana × Iris xiphium).
Two varieties of Iris xiphium (var. praecox) from Spain and (var. lusitanica) from Portugal, were crossed with Iris tingitana (from North Africa). This was carried out by a Dutch bulb firm ‘Van Tubergen’ (based in Haarlem) in the 19th century.
Because the bulb could be forced in a greenhouse to flower early, it was popular with florists. Since the 1900s it has been crossed with other species to create various cultivars. After the Second World War, stocks of bulbs were imported to America. They then increased the color range, mainly the yellows.
Iris × hollandica has a bulb of about 10 centimetres (3.9 in) and can reach a height of about 60 centimetres (24 in). This bulbous iris has narrow linear green leaves and bears largish blue to yellow to white flowers. They do not have any fragrance. They mainly bloom in May–June in the northern hemisphere, and in September–October in the southern hemisphere.
II. How to Grow and Care
Sunlight
Dutch iris likes sufficient sunlight. It needs to receive more than 6 hours of light per day and can be planted in a garden with no shade. It can also grow in slightly shady environments, but the quality of its blooms and disease resistance may decrease. Some varieties tolerate environments with less light and can grow in the shade of other plants.
Temperature
plants of the Iris genus are mainly distributed in the temperate zones of the Northern Hemisphere. The majority of its species are hardy, except some dwarf species that require hay or bark to cover their roots to overwinter in cold regions. The need for water among different Iris species varies, too. Some Iris likes moist environments, and some species can even grow in water.
Watering
Different Iris species’ needs for water vary. Bearded iris requires very little water, and only needs to be watered when the soil is dry. Other species, such as Siberian Iris (Iris Sibirica), need much more water and require the soil to be kept moist all the time. Most species are intolerant of standing water. When planted in poorly-drained soil, their roots may rot.
Soil
Dutch iris likes loose, fertile, and well-drained soil, but can also grow in dry and barren earth. It likes slightly acidic or neutral soil with a pH value of 6.0-7.0. Sulfur can be added to improve alkaline soil, while lime can be added if the soil is acidic.
Fertilizing
Dutch iris likes soil rich in humus, so fertilize in the early spring, early fall, and before its flowering period. Before it blooms, use phosphorus-rich compound fertilizers, such as fertilizers with a 5-10-5 NPK ratio, to promote blooming and encourage more gorgeous flowers. Balanced fertilizers (20-20-20 NPK ratio) can also be used. Some organic fertilizers contain fewer nutrients but improve the soil, so it is also good for the plant’s growth. Water right after fertilizing to help the roots absorb the fertilizer.
Planting Instructions
Plant your Iris X hollandica bulbs from September to October-November. Give them enough time to settle in before cold weather hits. For container growing, you can plant at any time of year.
Dutch Iris welcomes all light, well-drained soils, preferably limestone to slightly acidic. Summer drought in sandy or rocky soil? Not a problem, they’ll just take a nap until things get better. But they truly despise heavy, waterlogged winter soil. Do them a favor and plant them in full sun, or maybe part shade.
Go for a mass effect by planting groups of at least 5 bulbs, spaced 4-6 inches apart (10-15 cm). But don’t go overboard with this iris, as its foliage quickly turns yellow in June, leaving the ground bare.
- Loosen soil thoroughly, adding sand, gravel, or potting soil if needed (5 shovelfuls of well-decomposed compost per square yard or meter) to improve drainage. You can even lay a gravel bed of about 1 inch (3 cm) just under the bulb.
- Place the bulb on its flat base, between 4 and 6 inches deep (10-15 cm). Planting that deep keeps greedy voles at bay!
- Cover with soil and water.
- Feel free to mark the location with a small sign or slender ornament.
Dutch Iris in a pot
Got a sunny balcony or courtyard? A wall in need of charm? You can grow Dutch Iris in a pot too! For pot or planter planting, stick with shorter varieties that are 16 to 20 inches tall (40 to 50 cm). Also does fine indoors.
- Pick a pot that’s both wide and deep enough to fit a party of 5 bulbs.
- Start with a drainage layer (clay pebbles or stones), then fill it up with a well-draining mix of sand, leaf compost, and peat.
- Plant your bulbs and give them a good watering.
Pruning
Cut off the bloom-bearing stalks after blooming to reduce nutrition consumption. Some varieties may bloom again. In the fall, prune old and dry leaves to improve the plant’s inner ventilation and prevent pests and diseases.
Propagation
Because seeding may result in changes in the colors and shapes of flowers, it’s best not to propagate the plant by seeding. Dutch iris can be propagated by division, and it is usually carried out 2-3 months after blooming. Divide the plant with a sharp knife, retaining a 15 cm-long rhizome on each piece. Cut off the old, dried parts and trim the leaves to 15 cm in length. Keep the plants 30 cm apart from each other (for dwarf varieties, the distance can be reduced to 15 cm).
Pests and Diseases
Not many pests attack Dutch iris. Rot is the most common issue in poorly drained soil. Improve drainage. Try planting on a mound or slope if needed.
Voles sometimes snack on bulbs. To avoid this, plant bulbs 6 inches (15 cm) deep. Slugs and snails may munch on leaves and flowers. Be vigilant and remove them in the evening.
III. Uses and Benefits
These plants are excellent for containers and cutting gardens.
The blooms can last up to 2 weeks, and many cultivars are popular for Easter arrangements.
As it’s a mid-sized plant, it provides a perfect backdrop for ground covers and shorter plants, especially in border displays.
They’re also at their best when planted in groups.
IV. Harvesting and Storage
Dutch iris flowers can be harvested for bouquets. Choose not-fully-bloomed flowers and cut them off from the stem base obliquely with a pair of sharp gardening scissors. Quickly put the flower in a vase with clean water to avoid its dehydration.