Summer bulbs add beauty to the landscape when earlier spring bulbs have long faded and flowering shrubs have turned to foliage for the season, said a University of Illinois horticulture educator.
“However, summer bulbs must be dug up at the end of your growing season and properly stored inside for the winter in order to have a floral display the following year,” Richard Hentschel explained.
By tradition, a bulb refers to any plant that maintains its entire life cycle in a storage root. A few of the well-known, common summer-blooming bulbs are lily, gladiolus caladiums, iris, canna, and dahlia. Summer bulbs are planted in the spring after the chance of frost and the garden soils have warmed.
To dig summer bulbs at the end of the season, Hentschel said to wait until the bulb foliage has naturally died down or dig immediately after a killing frost.
Digging summer bulbs usually means loosening the soil with a garden fork or spade several inches away from where the bulb is believed to be and gently lifting the plant without damage to the bulb itself, Hentschel said. “At this point, the outer skin of the bulb is soft and tender so caution is needed,” he added. “Most often summer bulbs are stored with a small amount of soil still clinging to the roots. A gentle shake to remove any excess soil will be a good step.”
Summer bulbs need to be cured before storage to toughen up the outer skin. Curing means allowing the freshly dug bulbs to dry down in a cool shady location before being stored. Summer bulbs that are put into storage still wet or damaged during the digging process could easily develop storage rots and other kinds of decay, Hentschel said. The time from digging to actual storage of the bulb for the winter can take a few days to a few weeks and should be done during warm late-summer and early-fall weather.
Hentschel recommended that if there are many different kinds of summer bulbs to store, labeling each clump should be done. “One neat trick for larger bulbs such as amaryllis or elephant ears is to use a magic marker and write directly on the bulb,” he said.
Storage temperatures for summer bulbs can range from 40 to 60 degrees, with 50 degrees being a good goal. If kept too warm, bulbs will begin to grow in storage, and, if they are kept too cold, they suffer and can be slow to grow when planted again in the spring. While in storage, check on the bulbs at least once during the winter months to be sure the bulbs are sound. “If any bulbs show decay, remove them before the decay spreads to healthy bulbs,” Hentschel said.
Some storage roots may need to have the soil or storage media moistened but never saturated to maintain adequate moisture so the storage roots are not all dried by planting time.
“With these easy steps, summer blooms will grace your garden year after year,” Hentschel said.