Plants use specialized underground structures called tubers to survive difficult conditions and reproduce. These formations are common in many popular garden plants. Understanding tubers is key to successfully growing and propagating a wide array of beautiful and productive additions to your landscape. Tubers efficiently store essential nutrients and energy for future growth.
What Exactly Are Tubers
Tubers are enlarged, fleshy underground structures that store carbohydrates, starches, and other nutrients. They enable plants to endure harsh environmental conditions like winter dormancy or dry spells. Tubers also facilitate asexual reproduction, allowing new plants to sprout directly from their stored energy.
There are two primary types: stem tubers and root tubers. Stem tubers, like potatoes, are swollen underground stems with “eyes” (nodes) that develop into new shoots and roots. Root tubers, such as those found in dahlias or sweet potatoes, are modified, enlarged lateral roots. Unlike stem tubers, root tubers lack “eyes”; instead, adventitious buds form at the end closest to the parent plant, enabling new growth.
Popular Plants That Grow From Tubers
Many popular garden plants grow from tubers, offering diverse forms and colors.
Dahlias, grown from root tubers, are known for their spectacular, varied blooms, making them versatile for garden beds and cut flower arrangements.
Tuberous Begonias produce vibrant, showy flowers throughout the summer, thriving in shaded or partially shaded areas.
Caladiums are celebrated for their striking, colorful foliage, displaying intricate patterns and shades. These tropical plants brighten shady garden spots or serve as houseplants.
Potatoes are widely recognized stem tubers, cultivated globally as a staple food crop.
Anemones, or windflowers, produce delicate, cup-shaped blooms in various colors from small, irregularly shaped tubers.
Ranunculus, grown from claw-like tubers, create rose-like flowers with thin petals, blooming abundantly in spring and early summer.
Planting and Cultivating Tuberous Plants
Successful cultivation of tuberous plants begins with proper timing and site selection. Plant most tubers, especially cold-sensitive ones, after the last frost when soil temperatures are above 60°F (15°C), typically late spring. Some varieties, like certain anemones, can be fall-planted in milder climates. Most flowering tubers prefer at least six to eight hours of direct sunlight for robust growth and abundant blooms. However, tuberous begonias and caladiums thrive in partial shade or filtered light to prevent scorching.
Well-draining soil is essential for all tuberous plants to prevent rot. Amend heavy clay soils with organic matter like compost or peat moss to improve drainage and aeration. A slightly acidic to neutral pH (6.0-7.5) suits most tuber varieties.
Planting depth varies: dahlias are typically planted 4-6 inches deep with the eye facing up, while smaller tubers like ranunculus or anemones need 2-3 inches of soil coverage. Spacing ranges from 8-12 inches for caladiums to 18-24 inches for larger dahlias, allowing ample room. After planting, water sparingly until sprouts emerge, as excessive moisture can cause rot. Once established, maintain a consistent watering schedule.
Storing and Dividing Tubers
In colder climates, lifting and storing tubers over winter is necessary for their survival. Begin this process after the first hard frost causes foliage to die back, signaling dormancy. Allowing plants to remain in the ground for a week or two after frost helps tubers cure and toughen their skins. After digging, gently remove excess soil and allow tubers to cure (dry) in a cool, dry, well-ventilated area for several days or weeks until stems are dry.
Store cured tubers in a cool, dark, dry location (40-50°F / 4-10°C) with moderate humidity (70-80%). Use dry peat moss, vermiculite, or sawdust as storage mediums to maintain humidity and prevent desiccation. Inspect tubers periodically throughout winter, discarding any showing signs of rot or shriveling.
Dividing tubers is a propagation method that increases plant stock and improves health. For dahlias, divide in late winter or early spring before planting, ensuring each section has at least one “eye” or growth point and an intact “neck.” Use clean, sharp tools for careful division.
Troubleshooting and General Tips for Tuber Care
Maintaining healthy tuberous plants involves addressing common issues and providing consistent care. If rot occurs, it often results from overwatering or poorly draining soil; ensure proper site selection and watering. Lack of blooms can stem from insufficient sunlight, inadequate nutrients, or improper storage; provide recommended sunlight and a balanced fertilization regimen. Pests are less common, but regular inspection aids early detection.
Established tuberous plants benefit from consistent moisture, but allow the soil to dry slightly between waterings. Fertilization supports vigorous growth and flowering; a low-nitrogen, balanced liquid fertilizer applied every few weeks is recommended for heavy feeders like dahlias and begonias. Taller varieties, such as many dahlias, may require staking to prevent stems from bending or breaking. Deadheading spent flowers encourages continuous blooming by redirecting energy to new flowers.