Dwarfs for Every Garden

by Tom Waters

The dwarf bearded irises (those classified as miniature dwarf bearded, or MDB) are a charming addition to any garden. With blooms held eight inches (20 cm) or less from the ground, they are the daintiest of all the bearded irises. They are also the earliest to bloom. In my garden, the first ones open a full two months before tall bearded season.

Almost all MDBs grown today fall into one of three categories. All three groups owe their existence to the eastern European species Iris pumila, which came to be used by American hybridizers in the 1940s.

'Liitle Drummer Boy'

The first category is Iris pumila itself. This tiny species is seldom more than 4 or 5 inches (10-12 cm) in height, with just one bloom per stem. (Actually, the stem is often almost nonexistent, most of the height being in the perianth tube formed by the flower parts themselves.) It comes in a range of colors from white and yellow to blue, violet, and purple, usually with a darker colored spot on the falls. There are a number of cultivars produced by hybridizers or selected from wild forms for their garden value. Some of my favorites are 'Little Drummer Boy' (Willott, 1997), 'Hobbit' (Miller, 2004), and 'Royal Wonder' (Coleman, 2013).

'Hobbit'

'Royal Wonder'

The next two categories came about as a consequence of the creation of the first standard dwarf bearded (SDB) irises in the 1950s. As I discussed in an earlier blog post, the SDBs were the result of crossing Iris pumila with tall bearded irises (TBs). The SDBs averaged about 12 inches (30 cm) in height and would typically have 2 or 3 buds. They are regarded as medians, not as true dwarfs, because of their larger size and occasional branch, something not seen in traditional dwarf irises.

'Alpine Lake'

Shortly after the SDBs appeared, hybridizers crossed them back to Iris pumila to produce irises of truly dwarf stature, but with a little something extra from their TB ancestry: plicata pattern, for example, or wider petals and more flaring form. These were the most common type of MDB in the 1960s, '70s, and '80s. 'Knick-Knack' (Greenlee, 1961), 'Zipper' (Sindt, 1979), and 'Alpine Lake' (Willott, 1981) are good examples of this type.

The third category came about from SDB breeding in an even more direct way. Sometimes crossing two SDBs produces an iris smaller than average. These small ones, if they are 8 inches or less in height, belong in the MDB class, since the definition for that class is based on height, not ancestry. Because so much work has been done to improve the SDB class over many decades, these are often the most "developed" dwarfs in terms of form and variety of color and pattern. Popular examples of this type are 'Dollop of Cream' (Black, 2006), 'Icon' (Keppel, 2008), and 'Beetlejuice' (Black, 2013).

'Dollop of Cream'

'Icon'

Generally speaking, the greater the amount of Iris pumila in a dwarf's makeup, the smaller, earlier, and more adapted to cold winters it will be. Those with less Iris pumila will have larger flowers with greater width and ruffling, a greater range of color patterns, and perform better in warm-winter areas.

There are no official designations for these categories, although hybridizers sometimes identify them by the number of chromosomes: Iris pumila has 32, the SDBs and their small MDB progeny have 40, and the SDB x pumila hybrids have 36.

How can you tell which of these categories and MDB belongs to? Alas, the only way to be sure is to look at the parentage on the Iris Encyclopedia or other resource. In most cases, this will lead you back either to SDBs or to Iris pumila, or else the parentage will be an SDB x pumila cross. If this sort of research interests you, my list of pure Iris pumila cultivars may help make sense of things.

I love dwarfs in all their variety, and happily live in a locale where all kinds grow well. Do you grow dwarfs in your own garden? Which kinds are your favorite?

The Earliest Irises: Welcoming Spring

by Tom Waters

reticulata iris 'Katharine Hodgkin'

While I enjoy the rest and simplicity that winter brings to the garden landscape, by January or February I find myself looking ahead eagerly to spring. Most gardeners think of irises as late spring flowers, bridging the time between spring bulbs and summer perennials. But there are many wonderful irises that bloom much earlier, and help the impatient iris lover through the long wait for bloom.

I garden in what is now zone 6 in northern New Mexico. (The older USDA map had us in zone 5). Here the last frost is usually in May. Tall bearded irises bloom in late May and early June. But my iris season begins in February, or sometimes even earlier!

Reticulata Irises

Iris danfordiae

The earliest of all irises in my climate are the reticulata irises (sometimes sold as “rock garden irises”). They often bloom right through the snow! These grow from bulbs, resembling crocus corms. They bloom along with the crocuses too, which is usually March here. However, I have a warm flower bed along the southeast side of the house, where spring bulbs bloom a month or more before those in the main garden. Here the reticulata irises are in full bloom in February; in some years they begin late in January.

reticulata irises blooming in the snow

These are small flowers, about the size of crocuses, though a bit taller. Most of the widely available ones are shades of blue, violet, or purple, often with a contrasting orange or yellow stripe on the falls. The earliest of all is the yellow Iris danfordiae. This little charmer has almost no standards, the shape of the bloom being formed by its wide falls and style crests. Its bright yellow color is accented by small leaf-green dots.

reticulata iris 'Cantab'

The blue, violet and purple forms in commerce are mostly forms and hybrids of Iris reticulata and Iris histrioides. Some of my favorites are the light blue 'Cantab' and the dark blue 'Harmony'. There are also white ones, and a lovely pastel blend of sky blue, cream, and gray tones, 'Katharine Hodgkin'.

These wonderful irises are available inexpensively almost anywhere you can buy crocuses, daffodils, and tulips. In some gardens, they multiply from year to year. Elsewhere, they may dwindle away. (Planting deeply may help.) But they are inexpensively replaced and well worth it for the cheer they lend to the late winter garden. It’s surprising that they are not as widely grown as crocuses or snowdrops. They surely deserve to be!

Dwarf Bearded Irises

Iris pumila

Iris pumila

Among the more familiar bearded irises, the earliest to bloom are the miniature dwarf bearded (MDB). Although these grow from rhizomes like their tall bearded cousins, they are less than 20 cm (8 inches) In height! An established clump presents a carpet of color before the taller ones are even sending up their stalks. These are available in a wide range of colors, patterns, and flower shapes to suit every taste.

Iris pumila 'Steppe'

In my garden, the bearded iris season begins with the species Iris pumila. This little gem is native to eastern Europe, from Austria to the Caucasus. Bloom usually begins here around the beginning of April, and carries on for a full month. The dainty, perky blooms come in violet, blue, yellow, cream, and white, often with a contrasting darker spot on the falls. They have hardly any stem at all, blooming right on the ground, with the tops of the blooms just a few inches above the soil. There are some named cultivars of the species, such as the well-known 'Little Drummer Boy', 'Suslik', and 'Hobbit', as well as more recent introductions such as 'Steppe', 'Royal Wonder', and 'Wild Whispers'. To find this delightful species, you will have to turn to specialist nurseries, either iris enthusiasts are rock-garden aficionados who seek out wild plants from around the world. Beware that there is an unfortunate practice in the nursery trade of labeling any small bearded iris as “Iris pumila”; if you see such a label at a local garden center or home improvement store, it is almost certainly not the real species.

Iris pumila 'Royal Wonder'

Iris pumila comes from regions where it is cold in winter. It does fine in my garden, where winter temperatures down to around 0 F are normal, but growers in warmer-winter climates report that it does not persist well for them.

There are two similar species, Iris attica and Iris suaveolens, that come from the southern Balkans, Greece, and western Turkey. It seems these might do better in warmer gardens, but they are not widely grown. Again, you will need to seek them from specialists.

Iris suaveolens

MDB iris 'Rosa Brooks'

Easier to find are the hybrid miniature dwarfs, derived from Iris pumila but with some tall bearded irises in their ancestry as well. These tend to be a bit larger than Iris pumila, and bloom later. Their time is late April into early May in my garden. Although not commonly found at garden centers, many commercial iris growers list some of them. These are available in all the colors seen in Iris pumila, as well as other colors from their tall bearded ancestry, such as pink, orange, plicata, and sometimes contrasting red or blue beards! They are quite adaptable to different climates, although most appreciate a winter chilling.

Some favorites of mine are'Alpine Lake' (white with a gentle blue spot), 'Icon' (bright orange with a darker spot) and 'Dollop of Cream' (ruffled creamy white).

MDB iris 'Icon'

By the time the miniature dwarfs have finished, iris season is well underway, with medians and arilbreds beginning to bloom and the tall bearded not far behind.

MDB iris 'Alpine Lake'

MDB iris 'Dollop of Cream'

I do love the head start on spring these earliest irises provide, but I would grow them even if they bloomed later. Their charm and daintiness speaks to me, and I enjoy the variety and fun they add to an iris collection.