Tender Summer Bulbs: Tips on How to Grow and Store Them

Tender summer bulbs include some popular varieties, such as dahlias, gladiolus and caladiums. Not all of these summer favorites are true bulbs. Many are tubers, corms and rhizomes. They are all classified as geophytes, but grouping them as bulbs is a habit for most gardeners. No matter what they're called, tender summer bulbs are beautiful and easy to grow.

These tender bulbs can be planted anytime after the ground warms sufficiently in the spring. This is the opposite of their spring-flowering relatives such as daffodils and tulips, which need to be planted in the fall. Summer bulbs can be purchased in the spring just before time to plant them. They can also be ordered months in advance from garden catalogs and delivered just before planting time.

Summer bulbs are referred to as tender bulbs because most of them can't survive freezing temperatures. Most tender bulbs must be dug and stored over the winter for USDA Zones 7 and colder. This doesn't seem to affect their popularity with home gardeners. Tender summer bulbs can be planted beginning in the spring and often the planting times can be staggered to extend the bloom times until fall.

Many gardeners often treat these summer bulbs as annuals and leave them to perish outdoors in the winter. An alternative method is to dig them and store them for the winter. This is certainly the more budget friendly way. Many of these summer bulbs are available at local garden centers already potted, growing and ready to enjoy. Don't forget to look for economical packages of tubers, bulbs, corms and rhizomes usually where seed packages are sold.

Begonias (Photo. 1)

These beautiful shade loving begonias shouldn't be confused with the annual fibrous-root begonias commonly sold as annual bedding plants. These begonias are grown from tubers and have several varieties of foliage and flowers available. Some are large doable flowering varieties available in brilliant hues of pinks, orange, yellow, white and red.

They are excellent as container plants and even in hanging baskets. Tuberous begonias will do okay if they receive morning sun, but must be shaded in the afternoon. When I grow these in the mid-south, I give them shade all day due to the summer heat. They bloom nonstop all season.

Keep these begonias evenly moist in rich soil. Remove the tubers from the ground or container in the fall and allow them to dry. Remove the soil from the tubers and store in sawdust or vermiculite at about 40- 50 degrees during the winter. Hardy in USDA Zones 9-11

Caladium (Photo. 2)

These summer tubers are grown for their beautiful foliage. Caladiums don't bloom, but the leaves compensate for the lack of flowers. There are several caladium cultivars available and they are usually plentiful in garden centers in the spring. They have dramatic mottled and variegated bicolor or tricolor leaves in shades of pink, green, white, burgundy and red. Caladiums have heart or arrowhead shaped leaves and require full to part-shade. Keep them moist in the summer so they don't go dormant.

They look great planted in mass under trees or in containers with companion shade-loving flowers. They can stay in the ground until after the first frost and then remove the tubers to dry completely. Store the caladium tubers in vermiculite or peat moss in an area that maintains a temperature of 50-60 degrees during the winter. Another option is to enjoy them as houseplants if there is enough humidity in the home. Hardy in USDA Zones 10-11

Calla Lily (Zantedeschia)

The calla lily grows from rhizomes and they have a unique bloom. The flowers are actually spathes and several varieties emerge in a funnel shape. They come in a rainbow of colors and bloom for more than a month. Stagger the planting times in two-week intervals and enjoy these exotic looking plants for much longer.

Calla lilies are good candidates for containers. This is an ideal way to let them have the spotlight as a specimen. They need sun and moisture during the summer. Most calla lilies are listed as cold-hardy only to zone 7, but it's widely known that several varieties can cross that line and survive in zone 6.

In colder norther regions the rhizomes can be stored for the winter. After the first frost, cut the foliage back to about 2-inches and allow the rhizomes to dry in a warm place for one to two weeks. Then store them covered in peat moss, vermiculite or sawdust in 45-50 degrees. Another choice for callas is to keep them indoors as houseplants for the winter. Hardy in USDA Zones 7-10

Canna (Photo. 3)

The canna is definitely going to stand out in the crowd. They are large and beautiful with leaves that resemble the banana tree. Cannas are grown from rhizomes and come in several bright flower colors and foliage variations. The dwarf canna grows to about 3-feet tall and the regular canna can easily reach 6-feet in height. They fill an empty space with ease and make great foundation plants.

These plants are also listed as only cold hardy to zone 7, just as the calla lily. Some varieties of cannas can also grow in zone 6, but it's really a game of chance. Two varieties of cannas were planted in my USDA Zone 6b at the same time and location. One variety did not survive the winter and the other variety has been returning for about 5 years.

Cannas can be dug after the foliage has been damaged from a frost and begins to wither. The stems can be cut back to 4 to 5-inches tall. Allow the stems to dry and then pack the rhizomes in slightly moist vermiculite or peat moss. Cannas that are grown in containers can be left in them and stored in 40 to 50 degrees for the winter. The rhizomes will need to be kept slightly moist during the winter. Hardy in USDA Zones 7 - 10

Dahlia (Photo. 4)

The dahlia is one of the most popular summer flowers due to their diversity in size and color. The dahlias grow from tubers and have thousands of cultivars available. They range in size from 12-inches in height to giants reaching more than 6-feet in height. The flower sizes vary from about 2-inches to 12-inches in diameter and bloom in almost every color imaginable except blue. The giant dahlias are often called "dinner plate" dahlias due to their enormous flower size. The tall varieties will need to be staked to keep them erect. Dahlias are great as cut flowers for bouquets.

Give dahlias sun for adequate flowering, but in the hotter regions providing afternoon shade is recommended. They will need to be watered thoroughly once a week during the heat and drought of summer. Just don't over-water them when they are first planted. Although they like to stay moist, they need good drainage in the soil. Dahlias are good candidates for containers but be sure to give the giants a large pot.

Dahlia tubers will need to be left in the ground for about one or two weeks after the first frost. The tubers will need to produce new eyes during this time. If a frost doesn't occur, then cut the stems down to about 6-inches and this can start the process early. The tubers can be carefully dug after this time period.

Dig about a 12-inch circle and lift the tubers. There will be several tubers joined together, including young delicate tubers. Only the tubers that have developed an "eye" will grow the next season and the others can be discarded. The entire clump of tubers can be stored together and divided in the spring or separated now. Allow the tubers to dry for a day or two in a cool area. Store the tubers in a box or a paper bag filled with peat moss, vermiculite, sawdust or dry sand at about 40 to 50 degrees. If the tubers shrivel during the winter storage, add a small amount of moisture to the storage material. Hardy in USDA Zones 8 to 10 -marginally in zone 7

Colocasia (Colocasia esculenta)

This is a tuber grown for it beautiful large leaves and only as an ornamental in the United States. The tuber from Colocasia is used as food source in it's native southern Asia and West Indies. It might be easier to recognize by it's common name "Elephant Ears." The plant lives up to the common name because the leaves can get quite large. It brings a distinctive tropical flair to the garden. This tender plant makes a statement as it reaches heights of 4 to 8-feet tall.

The Colocasia does best in well-drained, moist, and richly organic soils. It can grow in sun or part-sun. In hot southern zones, this summer bulb will do best if given shade from the afternoon sun. It's often grown as an annual, but the tubers can be saved and used the following spring.

The plant can be grown in containers over the summer if preferred. In this case, just bring the containers indoors and let the plant go dormant for the winter. They can also be kept if a houseplant. If planted in the ground, dig the tubers after a frost has destroyed the foliage or the foliage begins to die back.. Cut the stems back to about 4 or 5-inches and store the tubers in mulch or saw dust at about 55 to 60 degrees. Hardy in USDA Zones 8 to 11

Gladiolus (Photo. 5)

These summer flowers are popular with florists and will be a great addition to the home cutting garden. Gladiolus are grown from corms and these corms will multiply over the summer. They are often referred to by their nickname "Glads" or occasionally by "Sword Lily" due to the tall slender sword-like leaves. They can grow to 5-feet tall and will need to be staked.

Give Glads plenty of sun but partial afternoon shade in hot climates is okay. Keep the soil adequately moist and wait for the flower show to begin around July. The flowers come in just about every color except blue. The flowers begin to open from the bottom of the long flower stalk first and then open gradually to the tip. If using the Glads as cut flowers, then cut them when the bottom flowers open. The flowers will continue to open after being cut and placed in the vase.

The Glad corms can be dug in late fall after the leaves have withered and turned brown. Cut the stems back to just an inch or two above the corms. The Glads will produce new corms on top of the original corm. Remove much of the soil and allow the corms to dry. Store them in a paper bag at 35 to 45 degrees. Hardy in USDA Zones 7 to 10

Tuberose

These tubers will grow through the summer and then produce a very fragrant bloom which a popular perfume ingredient. They bloom toward the middle to end of summer with white flowers in single or double form. Tuberose needs sun, heat and well-drained soil. The tubers will rot in a constantly wet soil. This makes them perfect for containers where the gardener can control the soil and provide good drainage.

Patience will be rewarded with a beautiful fragrant blossom on a slender stalk above the foliage. This makes their flowers ideal to cut and enjoy indoors. They will begin blooming three to four months after planting. They can often be purchased already growing in containers.

The tuberose foliage needs to be left as long as possible and allowed to yellow. The leaves can be removed after they yellow and the tubers can be lifted. Allow them to dry for several days. They need to be stored in a cool but not cold location at about 60 degrees. Place the tubers in peat moss in a box or paper bag for the winter. Check them periodically to make sure they aren't shriveling. Hardy USDA Zones 8 to 10