The term bulb can be used generally to refer to all bulbous plants, including corms, rhizomes, and tubers as well as true bulbs. In all bulbous plants, a portion of the plant is swollen into a food-storage organ that enables the plant to survive when dormant or when conditions are unsuitable for growth. However, the structures of all bulbous plants are not the same.
A true bulb is made of fleshy leaves or leaf bases. If you cut one open, you'll find concentric rings of scales attached to a basal plate. True bulbs can be separated into two groups: tunicate bulbs and imbricate bulbs. Onions, tulips, and daffodils are examples of tunicate bulbs; their outer scales form a dry, protective skin or tunic. The scales of imbricate bulbs, such as lilies and fritillaria, are separated and no tunic is formed.
Corms are formed from modified stem tissue. Unlike a bulb, corms have no visible storage rings; they consist of a solid stem or stem base. Corms are common in the Iris family, which includes crocuses and gladioli.
Rhizomes, made up of modified stem tissue, are usually more or less horizontal, underground stems. Some common examples of rhizomes are iris, ginger, calla lily, and lily-of-the-valley.
"Tuberous" is a term applied to many plants with swollen, often irregularly shaped stems or roots used for food storage. A true tuber is made up of modified stem tissues. It does not have any sort of basal plate like a bulb or protective covering. Potatoes, cyclamen, oxalis, and anemone are all examples of tubers.
Gather a variety of bulbous plants to create a stunning floral arrangement. Martha uses tulips, calla lilies, freesias, daffodils, and oxalis. Remove the leaves from the stems to prevent the water from getting slimy. Add one packet of plant food, such as Floralife, to the cool water, and place a frog at the bottom of your container. Add in one bloom at a time, and fill your container with a wide variety of colors.