Fall is bulb planting time. Most people are familiar with the basic bulbs such as daffodils and tulips, but what about some of the plants commonly called bulbs that are actually corms, rhizomes, tubers or tuberous roots? All of these terms refer to the specialized underground structures that are storage organs for many of our spring blooming plants. Through the growing season, they gather up nutrients building up reserves that will allow the plants to survive through dormancy and burst into bloom at the appropriate time.
A true bulb is, in essence, a baby plant surrounded by scales which are modified leaves held together at the base of the bulb. The papery outer layer is called a tunic, which some bulbs have and others, such as lilies, do not. Just like a coat, the tunic protects the bulb from drying out. Tulips, daffodils, hyacinths and narcissi are true bulbs.
Some other bulbs include the scilla, also known as bluebell, and grape hyacinth. Both show their heads early, foretelling spring. Scilla are bell- or star-shaped in colors from white to deep purple. Grape hyacinths spread very easily adding a lovely touch of purple-blue throughout a bed.
A corm is similar to a bulb, but it doesn’t have scales; rather it is a solid, swollen underground stem. It too may have a tunic. Crocuses and freesias are corms. An interesting twist is that there are spring and fall blooming crocuses.
A rhizome is actually a stem that grows underground or partially aboveground. Irises are the most common flowering rhizomes in our climate. A tuber is also a swollen underground stem, but it differs slightly from a corm in that its roots grow from all over, rather than from the bottom. Cyclamen and begonia are commonly grown summer tubers, but not hardy for fall planting in our area. Anemones and winter aconite are also tubers and most are suitable for fall planting.
Finally, there are tuberous roots. These are true roots, rather than modified stems. They grow in a cluster. Dahlias are an example of this. Dahlias need to be brought in for winter in this area.
Within in all these classes of spring flowers are multiple varieties of each. An infinite palette of colors, textures, growth patterns, fragrances and styles are possible. Explore the wonderful options available now for fall planting as you express yourself by creating a spectacular spring display.
JoAnne Skelly is Associate Professor & Extension Educator Emerita, University of Nevada Cooperative Extension. firstname.lastname@example.org