Heirloom Dutch Iris
If you are looking for heirloom Dutch Iris, you’ll be happy to know that some of our Iris hollandica varieties are moving into the heirloom range.
In the 1940s, the De Graaf Brothers and S. A. van Konijnenburg hybridized the award winning “Beauty” strain of Iris hollandica. These magnificent varieties are characterized by glorious ephemeral colors, larger flowers and often the growth of a second flowering stem.
Horticultural Zone Hardiness
Iris hollandica is good for horticultural zones 5 through 8. If your garden is in a zone or micro-climate that is too cold or only marginally appropriate, you may want to apply no more than a 2" layer of mulch after the ground surface freezes in the fall. The mulch should trap the cold temperatures into the soil, not warmth. Mulch helps to protect the bulbs from arctic temperature spikes. Good mulching mediums include straw, salt marsh hay or oak leaves. In the spring, you can loosen the mulch in the area in which the Iris will be sprouting.
Check your shipment against the packing slip and make sure that everything is as it should be. Occasionally, bags of smaller bulbs may be placed in the inner boxes of other bulbs to reduce jostling during shipment. If you can’t find something, open all of the inner boxes. If there is a discrepancy, please call us immediately so that we may resolve it with you. Since every bag or box of bulbs in your order has been scanned using its UPC barcode, we can usually tell you in which box each variety is located.
Iris hollandica bulbs look a little like teardrops. Inspect your bulbs carefully. We make every effort to ship you only healthy, firm, top quality bulbs. Little cuts, scars, discolored exteriors and dimples are normal marks from the flower bulb harvesting, cleaning and sizing processes in the Netherlands. Some bulbs may have a fully intact, papery skin while others have partial skins, and others may be skinless. The existence or condition of the skin has nothing to do with the performance of the bulb.
The most important factor is the way that the bulb feels and smells. As long as the bulb is firm, it is a good, viable bulb. Some bulbs may already have tiny baby bulbs developing on the basal plate (root base) of the bulb while others may even have a little top shoot. Some bulbs are prettier than others, but you can rest assured that all of the flowers will be gorgeous!
The top-size bulbs of Iris hollandica is 8 cm/up. If you find that one bag of Iris hollandica bulbs contains larger and smaller bulbs, it is because it contains 8 cm bulbs plus those larger than 8 cm. They are sized on conveyor belts in the Netherlands that have holes a hair under the 8 centimeter size. Smaller bulbs fall through these holes and are not included in our stock. All of the larger bulbs are included in our stock, and, as a result, there can be size variation. If any variety in any season produces a smaller top size bulb than expected, we note it on our website.
Bulb Storage Before Planting
After you’ve received your order and inspected it, keep the exterior carton and the inner boxes open to give the bulbs some air. All bulbs love good air circulation. Store them in a cool, dry place with low humidity, away from heat, frost and strong sunlight at about 50°F to 70°F. Never put flower bulbs in the freezer! Poor storage conditions could cause bulbs to dry out, or to become moldy.
Select and Prepare the Planting Site
You’ll need about nine bulbs per square foot. Square footage is determined multiplying the planting site’s length by its width.
All Dutch Iris require neutral pH and well-draining soil. The best soil is a sandy loam. For clay soil, break up the clay about a foot deeper than the planting depth of your bulbs and amend the bed with well-aged neutral-pH compost. For excessively sandy soil, amend the bed with peat moss and aged leaf compost.
Please do not ever add horse manure, chicken droppings, mushroom compost or other hot manure or compost to your flower bulb beds. If you would like to add compost you’ve made yourself, please make sure that it has a neutral pH and is completely decomposed and healthy. Partially decomposed compost can spread fungal disease, such as botrytis blight and nasty pests. What is good for vegetables is not necessarily good for flower bulbs.
Dutch Iris prefer full sunlight but can handle filtered sunlight or part-day sunlight. They also like a spot that tends to be warm and rather dry in the summer months
Easy to Plant
Dutch Iris bulbs are so easy to plant and are low maintenance. We'll ship you the bulbs in time for planting in your garden in the fall, once the ground has chilled down to about 55°F, after about two weeks of sweater weather when night time temperatures have hovered in the 40s. This is the best time to plant. Flower bulbs do everything in response to temperature and sunlight.
We usually recommend planting Dutch Iris bulbs 6” deep and 6” apart to allow for growth over time if they are being perennialized. If you intend to use them in a cutting garden or to replant every year, they may be planted 4” deep and 4” apart.
Please do not put anything in the bottom of hole that you’ve dug for the bulbs. Nestle the bulb into the hole, fill in the hole with soil to the level of the bed, and tamp down the soil lightly, making sure that individual holes are no longer apparent and that the garden bed surface is level. This will help to prevent water from filling up any of the individual planting holes excessively. All flower bulbs hate to get wet feet.
If you would like to do a layered or lasagna planting, first plant the Narcissi or Tulips to the proper depth and spacing, then cover them with enough soil to bring the Dutch Iris bulb planting depth to 4”. Then, place all of the bulbs over the surface (4" to 6" apart) and cover them with soil even to the surface of the bed.
Never put anything, including fertilizer, in the bottom of each bulb planting hole. Plant the bulbs to the proper depth and spacing, tamp down the soil and broadcast a 5-10-5 or 4-10-6 granular organic fertilizer over the surface of the bed as if you were feeding the birds.
While all flower bulbs are nature’s perfect little packages and will bloom beautifully the first year, we recommend broadcasting fertilizer three times a year for all perennial and naturalizing flower bulbs. First at the time of fall planting to help grow the roots, second when the sprouts emerge in the spring to help nourish the foliage and flower, and finally when the flowers start to die back, to help feed the bulb itself. (Bone meal is incomplete nutritionally and can attract animals to some varieties of bulbs.)
Do Not Plant Bulbs in Exterior Containers or Raised Beds
Flower bulbs should never be planted in outdoor containers, window boxes or raised beds where bulbs experience temperature spiking and repeated cycles of freezing and thawing. This results in root growth failure, root system destruction, frozen bulbs and/or bulb rot from poor water drainage. Flower bulbs must have a consistent cold winter temperature with good water drainage in order to produce a mature root system that will permit foliage growth and flower production in the spring.
Bloom Times, Size and Color
The bloom time listed for each variety is for horticultural zone 5 in normal spring conditions. The warmer the horticultural zone, the earlier flower bulbs will bloom. The colder the horticultural zone, the later flower bulbs will bloom in the spring.
Blooming in May and/or June in horticultural zone 5, deer- and rodent-resistant Dutch Iris grow from 18" to 22" tall with long, slender foliage. After the flowers fade, allow the foliage to die back naturally for prolonged photosynthesis to help the bulbs grow and multiply in future years. Once the foliage dies back, it may be raked and discarded.
Flower bulbs do everything in response to temperature, sunlight and site conditions. Bloom times, heights and colors are approximations affected by temperature and site conditions regardless of the calendar date. If it is a warm spring, bulbs will bloom earlier. If it is a cold spring, bulbs will bloom later. If it is a long cool spring, followed by rapid warming, you may find odd bedfellows blooming together.
In the event of a mild winter or a warmer-than-usual spring, flower bulbs that have emergent stalks with set buds may bloom early, small and short, although they will likely grow taller and larger as temperatures moderate. Temperature spikes can also affect mature root development, the actual form of the flower or the process of flower color maturation.
The most important thing to remember in the Spring is to enjoy your garden! Create big and little reasons to be outside, hold an annual Spring flower party, take notes on what you love and how all of your bulbs are doing, and take photos of where you need to plant more. Don’t forget that Dutch Iris make phenomenally good cut flowers!
Make sure no one weeds out your emerging Dutch Iris in the spring!