These irises grow up to a maximum height of 8 inches (20 cm) and their blooms reach a height of just 2 inches (5 cm) to 8 inches (20 cm). Miniature dwarf bearded irises are of pumila types and do not have regular stems. Their blooms appear on lengthened perianth tubes. When we talk about the perianth vis-à-vis the iris blooms. Miniature dwarf bearded irises are the smallest among all iris varieties and they also bloom earlier than the other irises. These irises are not only attractive, but also a dependable selection, especially for rock gardens. Miniature dwarf bearded irises are also the best choice when you plant them in drifts to produce a multihued carpet-like effect in your garden during the beginning of spring. These irises are small and elegant, especially attractive at the onset of spring when the harsh winter is gone and the iris clumps start bearing their vividly hued small blooms.
Most miniature dwarf bearded irises have been derived from the species Iris lutescens (syn. I. charmaeiris) and Iris pumila. The former iris species is indigenous to the arid rocky regions of southern Europe. As the blooms of I. lutescens come in a wide assortment of hues - violets, yellows and sometimes even white, this iris is called by several names. Sometimes, I. lutescens has also wrongly been called Iris pumila, and this has led to further confusions. In fact, for several centuries, people have commonly called the dwarf irises as pumila irises.
Chromosome counts as well as cytogenetic studies undertaken in recent times have helped to clarify the connection between Iris pumila and Iris lutescens - the two main forerunners of the miniature dwarf bearded irises. It has been found that a number of iris varieties that were once believed to be pure Iris pumila are actually the natural crosses of Iris pumila and Iris lutescens. One such iris variety is "Atroviolacea", a very popular cultivar known to growers since the middle of the 19th century and it is often known as the cemetery iris. The early settlers in North America carried this iris variety along with them almost throughout the continent and normally grew the plant to cover graves. Although not equally popular, other such varieties called "Azurea" and "Coerulea" were also cultivated from as early as the 1880s.
Since Iris pumila was introduced in the United States, it has been used as the original parent of three diverse iris classes - the standard dwarf bearded iris, miniature dwarf bearded iris and the intermediate bearded iris. Originally, English soldiers returning home from the Crimean War brought this iris species to England. These early plants gradually led to the development of three main iris cultivars - "Carpathia" bearing yellow flowers, "Nana" with red flowers, and "Sulina", which bears violet blue blooms.
The flowering period of miniature dwarf bearded irises corresponds with that of the daffodils. Usually, they grow up to a height of 8 inches (20 cm), but some varieties may even be 10 inches (25 cm) tall. Generally, the flowering stems of miniature dwarf irises are branchless and the flowers measure about 2 inches to 3 inches (5 cm to 7 cm) across. These iris varieties come into bloom before all other plants belonging to the class of bearded irises. When cultivated in ideal conditions, the blooms of these irises should flare, rise higher than the foliage and also be excellently proportionate to the plants in general.
It is important to note that Iris pumila is the major species from which most of the present day miniature dwarf bearded iris cultivars have been derived. Miniature dwarf bearded irises bred from pure Iris pumila are a class by themselves. Majority of these cultivars comprise anything between half to three-quarters of the genes of the older species Iris pumila. The remaining parentage of miniature dwarf bearded irises is usually complex. Rest of their genetic background comprises the tetraploid tall bearded irises or border bearded irises - the species I. lutescens having 40 chromosomes, and gradually more, Iris aphylla.
If you intend to grow or are growing miniature dwarf bearded irises, you ought to know that the color of the flowers of these irises differs from one year to another as well as from one garden to another. For instance, while a particular variety of miniature dwarf bearded iris may produce the sharp as well as clear spot pattern typical to Iris pumila in a particular year or in a particular garden, it may produce an indistinguishable spot pattern in the following year or in another garden. Then again, even varieties that are usually clear may have dark unequal blotching or streaking when the weather conditions are wet and cold. This aspect is more evident on blooms that are light-colored.
If you want miniature dwarf bearded irises to thrive in your garden, it is of utmost importance to provide them with a well-draining soil. In fact, this is one aspect that is vital for the growth and survival of these irises. Poor drainage will result in the plants to fail. At the same time, even a slight hint of dampness may be sufficient to promote rot. This is quite natural as originally, a number of the ancestors of miniature dwarf bearded irises were collected from the rock-strewn cliffs in the eastern regions of Europe and adjoining western Russia. This variety of irises also requires cold winters. It has been found that the number of blooms for most of the miniature dwarf bearded irises increases when the winter is colder.
Miniature dwarf bearded irises having a greater proportion of genes from Iris pumila are usually difficult to transplant. It appears that this variety of miniature dwarf bearded irises takes too long to develop roots. Often an entire clump collapses and eventually dies when transplanted - indicating they loathe being moved. On the other hand, miniature dwarf bearded irises not having a high proportion of I. pumila genes do well when transplanted.
Compared to other bearded iris varieties which flower afterward in the season, the miniature dwarf bearded irises do better when grown in more shaded locations. This is possibly owing to the fact that these irises come to bloom even before the leaves of the plants emerge. Miniature dwarf bearded irises have shallow roots and, as a result, they have a propensity to come to the soil surface in the freeze-thaw cycles. While the heaving of the roots does not create a problem in places where snow covers the ground during the winter months, it can be bothersome in places where the roots lie bare during the winter when there is very little or no snow at all. When the ground becomes frozen, you need to provide these smaller iris plants with mulching with hay or loose straw. At the same time, you need to be careful not to allow excessive soil accumulation on the rhizomes of miniature dwarf bearded irises, particularly in spring and summer, at a time when the plants are growing robustly.
You should also ensure that the miniature dwarf bearded iris beds are free from weeds. This is important because weeds not only deprive the irises of nutrients present in the soil, but are also likely to shade the plants. It is essential to remove the weeds often, especially after rains when the soil has become softer. The soft soil makes it easier to eradicate weeds.
In addition, while using fertilizers, you should always use a material or formulation that contains elevated levels of phosphorus. Read the label on the fertilizer container to ensure this. Scratch the soil around the miniature dwarf bearded iris plants and apply the fertilizer proportionately.