Understanding Flower Bulbs: The Five Types and How They Grow

Bulbs are among the most beautiful, interesting, and easy-to-grow flowers. Tulip mania in 17th-century Holland made them famous; today they’re loved for scent, color, and shape. Popular bulb-grown flowers include tulips, crocuses, daffodils, irises, lilies, daylilies, dahlias, and snowdrops.

All bulb plants grow from underground structures that store nutrients and energy. Though collectively called “bulbs,” there are five distinct types:

1. True Bulb

An underground stem base containing an embryonic plant with leaves, stems, and flower buds ready to emerge. Surrounded by overlapping scales (modified leaves); basal plate at bottom holds scales and produces roots. Examples: daffodils, tulips, lilies. Susceptible to dryness; can live years unplanted if cared for.

2. Corm

Solid stem base, no scales. Roots grow from basal plate; growth point at top. Examples: gladiolus, crocus. Lasts one season; new corm forms atop old one; small cormels appear at base.

3. Tuber

Underground stem base without basal plate. Roots grow from base and sides; multiple growth points on top surface.

4. Rhizome

Thickened stem growing partly or wholly underground. Main growth point at one end; additional points along sides. Best known: bearded iris.

5. Tuberous Root

Not a true stem; fibrous roots absorb nutrients from sides and tip. Swollen parts radiate from a central point. Growth points on bases of old stems, not roots. Examples: dahlias, daylilies.

Knowing these differences helps you plant, care for, and propagate each type successfully.