Iris Bulbs vs. Iris Rhizomes

Iris bulbs can be classified into two categories--those having bulbs and those having rhizomes. Irises are lovely flowers to behold and come in a variety of rich and vibrant colors, easily polishing up any landscape with their beauty. Iris can be blue, purple, yellow, brown, orange, pink, red and black.

As many as 200 different species of the iris bulb have been identified. Apart from their vibrant beauty, iris bulbs are also propagated for cosmetic and medicinal purposes. Since they grow in various environments, including deserts and swamps, you can easily grow them in your garden.

You can transplant them using the bulbs or the rhizomes. The following information can help you compare the two.

Bulbous Iris

The bulbs of the bulbous iris are smaller than those of the rhizome iris and they produce smaller blossoms. The iris bulb is similar to an onion bulb with fleshy inner layers set in a concentric pattern and a considerably thinner outer layer. The bulb acts as a storage organ. When the bulb is in the growing phase, roots appear at the bottom of the bulb and are referred to as the basal plate. It is best to transplant the bulb when the iris foliage has wilted. This usually occurs after flowering and the bulbs usually go dormant after blooming.

You should thoroughly prepare the ground before transplanting. Dig the ground well and apply compost and a good slow release fertilizer to boost the soil nutrient content. This will improve the structure of the soil and enhance drainage capabilities. Peat moss or well-rotted manure can be used as an alternative to compost.

Rhizomes Iris

Rhizomes are thick roots that grow within the ground or slightly above the soil in a horizontally aligned position. They look like long potatoes and grow through root separation. The lower surface yields roots. New rhizomes usually develop annually from the original portion and extend to the surrounding area as they grow. The rhizome iris typically grows into a large mass and produces fewer flowers after the third and fourth years. Transplanting the rhizomes should be done in the late summer for best results.

Before transplanting the iris bulb, you must first reduce the height of the leaves by about one-third. Use a digging fork or spade to lift out the whole clump and divide the rhizomes using a sharp knife. Make sure that each new rhizome has a sturdy rhizome with roots and adequate foliage. Avoid placing new transplants too deep into the soil. Make sure that they are partially uncovered when transplanting. Old rhizomes should be removed and disposed of.

The bulbs of the rhizome irises produce small leaves that resemble swords in an overlapping arrangement. The Beardless, Bearded and Crestless irises are the most common variety of the rhizome iris.

Care of Iris Bulbs

Spreading a thin layer of compost around the stems every spring will benefit the plants. Apply mulch on frozen ground. Once the flowers begin to fade, cut the stalks to base level.