It’s time to preserve dahlia and begonia bulbs |

It’s time to preserve dahlia and begonia bulbs

— The days are getting cooler and shorter. Fall will be here before you know it. For gardeners, there is work yet to be done. If you succumbed to the beauty of dahlias and tuberous begonias when selecting bedding plants last spring, the task of preserving them is added to your fall to-do list.

Dahlias and begonias belong to a special group of bulblike perennials. There are five different types of bulbs. Dahlias are tuberous roots and begonias are tubers. In addition, there are true bulbs (daffodils), corms (gladiolus) and rhizomes (iris). All bulb plants hold a reserve of nutrients in a swollen underground storage area. All of the nutrients needed to complete its life cycle are in this storage area. They are almost guaranteed to produce blooms the first season planted provided they are planted properly. However, to obtain blooms in subsequent seasons, the roots must be lifted and properly stored. Follow these simple steps and enjoy beautiful plants again next summer:

The tuberous roots of the dahlia grow in a cluster, with the swollen roots radiating outward. Dahlias grow in Zones 3 and up, and although their tuberous roots might survive our cold winters, they tend to rot during the spring thaw. For that reason, they should be dug up each fall and stored for the winter. After frost has blackened the foliage, cut it off to leave 2-3 inches of stem above soil level. Carefully dig around the root cluster with a shovel and lift gently to avoid damaging the cluster. Nicking or damaging the tuberous roots leaves them susceptible to disease. Gently shake soil from the cluster and allow it to dry out of the sun for several hours or overnight. Hold the cluster by the stem and cut the tubers from the crown using a very sharp knife. Discard the original plant and any tuberous roots that show signs of damage. Remove all soil and pack for storage. Dahlias store well in dry sand or perlite, layered no more than three rows deep. Don’t forget to label your storage box. They need cool temperatures (40-45 degrees) but must be protected from freezing.

Tuberous begonias are tubers where the underground stem base is swollen. Tubers have one swollen area whereas tuberous roots have many. Healthy tubers will produce growth buds, called eyes, on the top of the bulb. To divide, simply cut into sections being sure you have at least one eye in each section. As with dahlias, lift the tubers after the plant has withered following the first frost. If they were potted, carefully remove from pots. Remove the soil from the tuber and allow it to dry out of the sun for two or three days. Following the instructions for dahlias, package and label for storage.

With proper preparation and storage, you can enjoy dahlias and tuberous begonias for years to come. Just remember that they are waiting for the right combination of moisture and temperature to trigger the beginning phase of their cycle. Dry sand and cool temperatures should hold them through the winter until you are ready to pull that trigger by planting them next spring.

Louise Poppen is a Master Gardener through the Colorado State University Cooperative Extension office in Routt County. Questions? Call 879-0825 or e-mail

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