You may not realize at first glance, but the common garden iris has a lot going on under the surface. There are a wide variety of iris types, and thus underground root systems, of this surprisingly complex species. Go beyond the typical bearded iris of your grandmother's garden, and you will find tuberous rhizomes, fleshy roots and bulbs all waiting to be discovered.
Iris germanica, or bearded iris, are recognizable by the double sets of three petals, three standards facing upwards and three falls cascading down. The falls are bisected with a fuzzy line, which imparts the beard term to this species. The bulb these tall spring flowering bloomers come from is a rhizome. Look for a tan, tuberous-shaped root that appears highly textured and bumpy. Roots grow down from the horizontal portion, and braided-looking, fan-shaped leaves extend from the top side.
Also termed beardless iris, these beauties are sleeker looking than their bearded cousins, although they retain the six-petaled, familiar form. Blooms will vary from the purple and blue family to white and yellow or respective mixes of these colors. Like bearded iris, Siberian iris grow from a fleshy rhizome or thick root that is planted just under the soil surface. The leaves will arch up from the crown of the plant, creating a vaselike shape with the foliage.
There are many types of dwarf iris, and each grows from a more bulbous, round-looking rhizome that is 5 to 8 cm in circumference. The bulb should appear firm and light-brown or tan in color. Blooms appear on stalks seldom taller than 6 inches and include species such as Iris cristata (dwarf crested iris) and Iris pumila (dwarf bearded iris).
Japanese iris, or Iris ensata, forms a more flat-looking bloom with often double the number of falls and ruffled-looking petals. These species, which are often several feet tall, grow from a thick, tan rhizome best grown from just under the soil surface.
Iris reticulata blooms from a typical bulb structure. A shorter plant that emerges in early spring as a complement to tulips and daffodils, this low-growing iris comes from bulbs 8 cm or more in diameter. These bulbs are rounded at the end with a flattened, basal plant from which emerges the roots. The shoot, or iris stalk, emerges from the pointed nose or bulb top. The body of the bulb contains scales covered by the papery tunic, which provides protection.