With a bulbous iris, you can create wonderful pictures in living colors in your garden. Moreover, you’ll come to treasure them for the beautiful arrangements which are so easy to achieve with their long-lived flowers.
They are known as the florists’ iris, and few flowers are perfect for cutting. Nor do many display their exquisite beauty with their delicate, orchid-like features and brilliant, glowing colors.
Most irises grow from rhizomes; the bulbous iris grows from bulbs. And I should forewarn you: they are not quite as hardy as the other irises.
But given winter protection such as that which is provided by evergreen boughs or by mulches like salt hay, they can survive our Northeastern winters.
Major Groups Of Bulbous Iris
Our Midwestern winters, however, are too severe for them. In the Mid-South and even in the Lower South, where the bearded iris fails, the bulbous iris comprises four major groups, all of which are beardless:
- Iris Reticulata, a miniature species
- The Dutch Iris, which are hybrids
- The Spanish Iris, I. Xiphium
- The English Iris, Xiphioides
These bloom in succession, in the order named, from late February through June. The bulbs are planted in autumn, the Dutch iris at a depth of 6” inches and the others at a depth of 4” inches.
Iris Reticulata
I. reticulata, which is native to the Caucasus Mountains, is grown along our Atlantic Coast, in the Canadian provinces of Quebec and Ontario, and on the Pacific Coast from Southern California to British Columbia.
The name is derived from the fact that the bulbs are covered with a fibrous network. I. reticulata and its closely related hybrids demand a sunny location and well-drained soil.
They are tiny, low-growing iris plants that are ideal for the rock garden or for planting about rock outcroppings and along garden pathways.
They bloom with the crocus in February and March and grow about as tall. You can either leave them in the soil or lift them.
They persist year after year, multiplying quickly to form clusters. You should plant them rather densely in drifts or ribbons for a grand effect. They can be grown easily in pots for flowering indoors during January.
Most Common Species
The most common is the species, I. reticulata, with its brilliant deep purple flowers bearing a golden blotch and a delightful violet fragrance.
Some iris specialists offer hybrids of Iris reticulata in other colors. For example, these may represent I. reticulata x I. histrioides crosses.
Cantab is a pale blue; J. S. Dijt, is a reddish-purple; Hercules and Royal Blue shades of purple.
Several other quaint miniature species of bulbous iris resemble reticulata. I. Danfordiae is a remarkable little species, ideally suited to the rock garden.
It has vibrant yellow flowers. Another, I. Vartani, has been known to bloom in early January in the latitude of the State of New York.
I. histrio, I. histrioides and I. persica, too, are interesting early-flowering miniature species. Most of these miniature species of bulbous iris are but little known in our country.
Dutch Iris
The Dutch iris is the most spectacular and exciting, the largest flowering and tallest growing of all the bulbous iris.
They reach heights of 18” to 26” inches, are the strongest growers, and have the largest bulbs.
The Dutch iris is the most important and the most modern of the bulbous iris. They are constantly being improved; the breeders in the Netherlands continue to introduce important new ones—larger, earlier, more vigorous, and more colorful.
The Dutch iris has tended to replace the older Spanish iris, their most important parent.
They originated in this century by Dutch hybridizers who crossed varieties of the Spanish iris.
Since then, they have been further hybridized by crossing with the very early Moroccan iris, I. tingitana, and I. Fontanesi.
Iris Fontanesi has been crossed here in the United States with a blue Dutch iris, giving the wonderful dark velvety purple Dutch iris that we know as National Velvet.
In northern areas, the Dutch iris should be planted 6” inches deep and as late as possible; the best time is just before the ground freezes.
They start some iris foliage growth shortly after planting and consequently require mulching to protect this new foliage. In addition, they need a sunny location and well-drained soil.
Both the Dutch and Spanish iris are short-lived in northern areas. But their bulbs are so inexpensive that most gardeners will find it worth their while to replace them frequently.
Where To Plant Dutch Irises
The scant foliage of the Dutch iris demands that they be massed. Plant in clusters, one variety to each cluster, as an early spring accent in the perennial border.
They are excellent when placed behind low-growing plants and when interplanted with tulips, daffodils, and hyacinths for a succession of blooms.
Since they are unsurpassed as cut flowers, you may want to turn over a section of the cutting garden to them.
When cutting, do not clip their stems too close to the ground; new flower buds may develop if they are not clipped too closely.
Dutch Iris Bulbs For Cut Flowers
Florists force quantities of Dutch iris bulbs for cut flowers. To prepare bulbs that will bloom early and uniformly for florists, bulb growers subject the bulbs to humid heat-curing at about 90° degrees Fahrenheit for 10 days and then store them at about 50° egress Fahrenheit for six weeks.
When set out in the greenhouse around October 15, such bulbs bloom well in December and January, depending upon the variety.
Wedgewood, which has blue standards and lighter blue falls, is in great demand for this purpose.
Treated Bulbs in Greenhouse
You may want to try some of these specially treated-bulbs in your home greenhouse. If so, see that yours are planted shortly after delivery in the fall.
Plant 2” inches apart and 2” inches deep. Keep them outdoors in flats or pots until just before the first hard freeze. Then place them in the greenhouse at a night temperature of 50° degrees Fahrenheit.
Raise the night temperature to 55° degrees Fahrenheit just before flowering is anticipated.
Dutch Iris Varieties
There are such wide good varieties of Dutch iris in such a wide range of colors that it is difficult to make recommendations.
My favorites for display planting in the flower garden include the following:
- Pride of Holland, a tall stemmed golden-yellow giant
- White Perfection, a new large white
- H. C. Van Vliet, which has deep violet-blue standards and pearl-blue falls
- Mauve Queen, mauve and lavender
- King Mauve, orchid
- Blue Triumphator, clear blue
- Lemon Queen, which has pale yellow standards and golden falls
All of these varieties bear giant flowers that tend to open in May and early June in the Northeast.
Spanish Irises
The varieties of Spanish iris (I. xiphium) have been subjected to but little improvement. In many gardens, they have been replaced by the Dutch iris.
Nevertheless, the Spanish iris still has value because they come into flower about two weeks after the Dutch iris and thus are useful in extending the springtime iris season.
They, too, require good drainage and sun. Few varieties are listed nowadays in the catalogs.
Recommended varieties include:
- L’ Innocence, Queen Wilhelmina, and British Queen, all whites
- Enchantress and Excelsior, blues
- Thunderbolt, a late smoky bronze
- Cajanus, a tall, clear yellow
English Iris Growth
English iris grows wild in the wet cloud-blanketed alpine meadows of the Pyrenees in Spain and France.
They are native to this region, but since the Dutch first imported them from England, they incorrectly named them “English” irises.
As the previous implies, the English iris demands moist conditions and thus thrives in the wet areas of our Pacific Northwest.
Elsewhere they do not flower so well and must be replaced every year or two. Unless you live in a moist locality, you will succeed better with one of the other bulbous iris. But do grow some bulbous iris; you’ll be rewarded.
44659 by Oscar Keeling Moore