Rhizome or Bulb?
A rhizome, although it derives its name from the Greek term rhizomat or rhizoma meaning a mass of roots, is not a root, as all isarians should know, but a stem that grows along the soil surface. Either just below the soil surface or it, as we know, will crawl out and grow along the surface of the soil. Contrary to true roots which never have buds or shoots, the rhizome puts up true leaves and buds along the top of the stem (rhizome) into the lighted atmosphere above the soil with true roots growing into the moist nutrient rich soil of the rhizosphere below.
In an aside it might be worth noting, that the tendency to grow out upon the surface of the soil by the rhizome, may be a survival technique that evolved over time to protect it from the myriad of rot fungi and bacteria, which attack it with disastrous results on occasion. We are all aware of the beneficial effects of the open air and sunlight in stopping rot. It just may be that those on the surface survive better than those beneath the soil in adverse soil conditions.
Like the bulb, the rhizome does store plant nutrients with in it by elongating and swelling in diameter. These reserves are for the purpose of feeding the new sprouts until they can develop a rhizome and roots of their own, also supplying some of the nutrients for early spring growth and bloom. But unlike the true bulbs, I do not feel that the rhizome stores nearly the entire nutrients that are necessary for the spring bloom season. Experiments that I have made with Louisiana rhizomes indicate that a well-grown mature rhizome, supplied with water only, will bloom from the nutrients stored in the rhizome producing a fairly nice flower. The bloom thought, does not begin to approach the standard that the same plant exhibits when properly grown in a well-enriched soil.
Finally let us sum it up, the true bulbs, both tunicate and imbricate as well as the corm, have one thing in common with a rhizome, they are all consider to be modified stem structures, as opposed to the tubers and tuberous fleshy root which are modified true roots.
Bibliography:
A practical book for the home gardener is "Bulbs, How to Select, Grow and Enjoy" by George Harmon Scott, Published by HP Books, Inc. PO Box 5367, Tucson, AZ 85703