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.
This member of the Iridaceae family can be grown as either a perennial or annual based on temperature and moisture levels and comes in a range of colors that have expanded over the years.
Better known as the several common names:
- Dutch iris
- Dutch hybrid group
- Fleur-de-lis
- Florist’s iris
- Iris hollandica
The hybrid is also parent to a wide range of cultivars, such as:
- ‘Apollo’ – Blue-tinted white blooms with yellow markings
- ‘Blue Magic’ – Dark violet with bright yellow markings
- ‘Silvery Beauty’ – Pale blue and white petals with a yellow center
- ‘White Excelsior’ – Compacted white blooms with a bright yellow stripe
- ‘Yellow Queen’ – Pure yellow
Dutch Iris Care
Size And Growth
Dutch iris is a relatively slow grower and will grow to around 18″ to 24″ inches tall.
Individual plants tend to be about 3″ to 6″ inches wide, although they will slowly spread via offshoots when grown as a perennial.
Flowering And Fragrance
Among the different types of Iris varieties, Dutch irises are early bloomers that feather long-lasting flowers over a relatively short bloom period.
When planted in the fall, Dutch iris produce blooms the following spring, the exact timing of which depends on temperatures and the cultivar used.
Cultivars most often bloom at some point between Mother’s Day and Memorial Day, with individual flowers lasting 3 to 5 days and the overall show lasting about 2 weeks.
Blooms are 3” to 4” inches across, are usually multi-colored, and have a gentle fragrance.
The most popular hues are:
- Blue
- Bluish-purple
- White
- Yellow
However, you can also find cultivars displaying other hues like:
- Bronze
- Burnt orange
- Burgundy
- Gold
- Pink
- Purple
- Rose
One of the great aspects of this plant is that it can be forced to bloom out-of-season in greenhouse-like environments.
This allows many growers to enjoy the plant when it’s normally dormant.
Light And Temperature
As with most irises, the Dutch iris prefers full sun, although a bit of afternoon shade in regions where the sun gets harsh can help prevent scorching.
This hybrid prefers more temperate regions, and it grows best in USDA hardiness zones 5 to 9, although the plant will need a little winterproofing in zone 5.
When properly insulated, Dutch irises can survive temperature drops as low as -15° degrees Fahrenheit.
Indoors room temperature ranges are perfect, as are normal household humidity levels.
One fascinating detail of growing Dutch irises is that you can influence whether they’re annuals or perennials with ease.
Keep the plantain hot and dry summer weather (or an indoor facsimile) for perennial flowers, or give it some cool, moist summer weather to keep it as an annual.
Watering And Feeding
Dutch irises prefer about 1” inch of water per week, which is easy to maintain using the soak-and-dry method.
Here are the following tips to consider:
- Stick your finger in the soil and water when it feels dry 1” inch down.
- Use room temperature water and go slowly around the plant until you see seepage from the container’s drainage holes or the surface begins to absorb the water more slowly.
- Avoid watering when the plant goes dormant, as its bulb can rot easily.
- Outdoor plants will benefit from a 5-10-5 NPK fertilizer in fall, spring, and when the foliage dies back.
- For container plants, use a liquid houseplant fertilizer of the same ratio.
Soil And Transplanting
Dutch irises prefer neutral, well-drained soils, although they can tolerate a slightly acidic pH.
A sandy, loamy soil is best for outdoor plants, and most potting mixes will work perfectly well for container specimens.
However, most lighter garden soils will also work if you add plenty of organic matter.
When adding organic matter, avoid “hot” manures that can encourage fungal disease in Dutch irises, including:
- Chicken droppings
- Mushroom compost
Safe amendments include:
- Fine-ground bark
- Fully decomposed compost
Note that you may also wish to add some perlite or coarse sand to aid in drainage.
Your Dutch iris will need to be repotted and divided every 3 to 4 years.
During this time, you can discard the central bulb, which is nearing the end of its life, and replace the soil of container plants.
Grooming And Maintenance
It’s safe to cut the flower stems for displays while they’re in bloom.
You may also wish to deadhead spent blooms to encourage a slightly longer bloom time, although this won’t increase the period by much.
Once the blooming is over, you may do the following:
- Cut the flower stem off, but be sure to allow the leaves to remain until they’ve yellowed and died back.
- Prune the plant only when the leaves have died back or remove diseased foliage.
- Finally, when planting in zone 5, you will want to either add a 2″ inch layer of mulch over the plant to insulate it from the winter cold or overwinter the bulbs indoors.
How To Propagate Iris Hollandica?
Both seeds and offsets are viable methods of propagating this plant, although you will only be able to divide the offsets every 3 to 4 years.
Fleur-de-Lis Pests Or Diseases
Dutch irises are quite hardy and can tolerate a relatively wide range of conditions, as they are both deer and rabbit resistant.
The main infestation risk is the iris borer, although snails and slugs can also pose a problem.
Root rot is the primary disease risk, with the less common threats including:
- Botrytis blight
- Leaf spot
- Mosaic virus
As with all irises, the Dutch iris is toxic to both humans and pets.
Uses of Iris X Hollandica
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.