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Über Tubers

Large-Flowered Bellwort, MerryBells Photo by wisteriaandcowparsley.com

Get your garden in tuber-licious shape with these stunning tubers that are best planted in fall.

By Mary Lynn Bruny

Good gardeners always plan ahead, and now is the perfect time to plant the following spring- and summer-blooming tubers.

Tubers-intro

These delightfully uncommon species, suggested by Panayoti Kelaidis, director of outreach and senior curator at Denver Botanic Gardens, are worth finding spots for in your garden. Most are available at nurseries either in pots or bare root. If not, they can be found online.

Italian Arum Photo courtesy geolocations.ws
Italian Arum Photo courtesy geolocations.ws

Italian Arum Latin name: Arum italicum Size: 1-to-2-feet tall, 2-foot spread Sun needs: Part to full shade Bloom season: Mid-spring to early summer Flower colors: White flowers, yellow spike, orange/red berries

This plant has it all: veined, glossy leaves, pretty white flowers followed by yellow spikes, and then dramatic orange-red berries on 8-inch stems. What’s not to like? “Stinky flowers,” Kelaidis admits, “but only for a day!”

The eye-catching berries last long after the leaves fade, and are the most dramatic part of the plant. Gardeners use Arum italicum to underplant with hostas as they produce foliage sequentially; when the hosta withers away, the Arum italicum replaces it, leaving the ground covered. Plant it in a protected location, as it’s not reliably winter-hardy. All parts of the plant are toxic, so it’s not recommended for areas where children and pets play.

Solomon's Seal Photo by Kukuruxa
Solomon’s Seal Photo by Kukuruxa

Solomon’s Seal Latin name: Polygonatum Size: Species specific, from 1-to-8-feet tall Sun needs: Part to full shade Bloom season: Spring to early summer Flower color: Greenish-white

Polygonatum has gracefully arched stems and symmetrical leaves with pearlescent strings of delicate, bell-shaped white flowers daintily attached. With species ranging from 1-to-8-feet tall, any shade garden can accommodate one. “This plant is spectacular, easy to grow and a wonderful statement in the woodland garden,” Kelaidis says, adding, “It’s extremely fashionable.”

Polygonatum grows easily in the moist shade garden, but will also grow in somewhat dry conditions so long as the soil has adequate nutrient levels. Plants can be lifted and easily divided every few years in the fall. Polygonatum is a lovely companion to hostas, ferns, pulmonarias, bleeding hearts, toad lilies and other shade-loving plants. It works very well in mass plantings or as a vertical accent among more mounded plant forms.

Winter Aconite Photo by Copit
Winter Aconite Photo by Copit

Winter Aconite Latin name: Eranthis hyemalis Size: 2-to-8-inches tall, 6-inch spread Sun needs: Sun to part shade Bloom season: Early spring Flower color: Yellow

This charming buttercup-like plant has a mass of single, lemon-yellow flowers up to 1½-inches wide sitting atop frilly collars of deeply lobed, bright-green leaves. Ideal companions include snowdrops, crocuses, Siberian squills or other small bulbs and plants that bloom in early spring. Plant the tubers 3 inches deep and 4 inches apart in moist, porous soil. For best success when dividing, separate into small clumps instead of single tubers.

Dragon Arum, Voodoo Lily Photo by Panayoti Kelaidis
Dragon Arum, Voodoo Lily Photo by Panayoti Kelaidis

Dragon Arum, Voodoo Lily Latin name: Dracunculus vulgaris Size: 3-feet tall, 2-foot spread Sun needs: Part sun to shade Bloom season: May to June Flower color: Purple and black

If you want a bold, dramatic tuber, look no further. The very exotic Dracunculus vulgaris steals the show with dramatic, foot-long purple-black blooms atop attractive, upright foliage. “It comes and goes in two months,” Kelaidis says, “but during that time it makes quite a statement.” And not only a visual statement: “It stinks to high heaven for one day when it’s blooming,” he says. Consider this when choosing a planting location!

Common in the Mediterranean, Dracunculus vulgaris prefers good, rich soil. Give the plant some wind protection or the stems may break. Large-flowered dahlias make suitably striking companions.

Foxtail Lily Photo by Brykaylo Yuriy
Foxtail Lily Photo by Brykaylo Yuriy

Foxtail Lily Latin name: Eremurus Size: 4-to-12-feet tall, 2-foot spread Sun needs: Sun Bloom season: Late spring to early summer Flower colors: White, pink, yellow, orange

Eremurus is magnificent in large borders against a wall, fence or background of dark-green foliage. This amazing and imposing lily relative has bell-shaped, ¼-inch-to-1-inch-wide flowers massed closely on graceful, pointed spikes.

“We use these all over the Denver Botanic Gardens,” Kelaidis says. “They are all through our perennial borders.” Eremurus disappears in June, so group it with species such as daisies, asters and chrysanthemums that will fill its void.

Plant Eremurus in rich, fast-draining soil, placing the crown just below soil level and the individual plants 2 to 4 feet apart. Handle the thick, brittle roots carefully; they tend to rot when bruised or broken. When leaves die back, mark the spot and don’t disturb the roots. For best success, provide the plant with some winter mulch.

Tubers-Iris-bucharica-Photo-by-Panayoti-Kelaidis
Juno Iris Photo by Panayoti Kelaidis

Juno Iris Latin name: Iris bucharica Size: 14-to-18-inches tall, 6-to-9-inch spread Sun needs: Full sun to part shade Bloom season: Mid-spring Flower colors: Yellow, white

Zippy two-toned flowers and a mass of glossy-green 8-inch leaves make this iris a standout. Bucharica provides multiple fragrant flowers over a long bloom period. Plant it with mid-season tulips, purple hyacinth and white daffodils for a beautiful display.

A native of the rocky slopes of Afghanistan, this iris performs in all types of soil, as long as it is well drained. Unlike most tubers, it thrives in dryer conditions, making it a good rock garden addition. It’s also perfect for forcing. Plant bucharica 2 inches deep and add bone meal. For optimal health, divide it every few years.

Wake Robin, Triplet Lily Photo by Hamiza Bakirci
Wake Robin, Triplet Lily Photo by Hamiza Bakirci

Wake Robin, Triplet Lily Latin name: Trillium Size: 1-to-1½-feet tall, 1-to-1½-foot spread Sun needs: Part to full shade Bloom season: Early spring Flower colors: Pink, purple, red, yellow, white, greenish/yellowish white

Trillium, a member of the lily family and native to U.S. woods, can be identified by its simple, yet fetching design: three leaves and three flower petals. “There are 30 to 40 varieties of Trillium,” Kelaidis says. “Twenty are available by trade, but the best one is grandiflorum.”

Once established, Trillium is not difficult to grow and will eventually spread in clumps. However it is particular about growing conditions; it thrives in moist, woodsy locations with companions such as columbines, ferns and toad lilies under deeper-rooted trees that won’t compete for moisture. During warm or dry summers, the plant may go dormant and die back to the ground, but don’t let the fleshy underground stems dry out.

Large-Flowered Bellwort, MerryBells Photo by wisteriaandcowparsley.com
Large-Flowered Bellwort, MerryBells Photo by wisteriaandcowparsley.com

Large-Flowered Bellwort, Merrybells Latin name: Uvularia grandiflora Size: 1½-to-2-feet tall, 1-to-2-foot spread Sun needs: Part to full shade Bloom season: Spring Flower colors: Yellowish white, yellow

Uvularia grandiflora makes an excellent focal center in the woodland garden. This member of the lily family is one of the mid-spring wildflowers found throughout much of the eastern half of the United States. The unusual leaves and flowers of the plant have a graceful, bowing, wilted look with the yellow bell-like flowers appearing as if they are loosened braids.

Uvularia grandiflora grows in any well-drained soil in medium to full shade. It spreads slowly to form attractive clumps. Plant with lower-growing spring flowers such as purple crocus.

Tuber Talk

If you’re not familiar with tubers, here’s some basic info on these interest­ing plants.

Tuber plants have thickened storage-root structures that supply water and nutrition during the winter. Once winter has passed, tubers use the storage root to reproduce themselves. There are “stem tubers” (also called “true tubers”) and “root tubers,” which reproduce differently. A good example of a stem tuber: the potato. It has leathery skin and lots of eyes, which are the growing points where new stems emerge. The daylily is a good example of the root tuber. It has many thickened root sacs, which are the growing points where new stems emerge.

Tuber plants come in two forms: potted or bare root. Each tuber species has its own planting requirements. However, all root-form tubers do best if soaked overnight in water before planting, according to Panayoti Kelaidis, director of outreach and senior curator at Denver Botanic Gardens. Tubers come into action after planting, growing all winter long, and this store of water helps get them going. “They will plump right up when you soak them,” Kelaidis says. Tubers need some moisture during winter; if the ground is continuously dry, tubers can’t grow and may die. Handle root tubers carefully; if they get damaged they may rot. And make sure to plant them upright. Many tuber plants have what appear to be rather quick life cycles, with both flowers and foliage dying back in the summer. They put on an extravagant show and then completely disappear until next year’s performance. “This is because the plant has done a lot of its growing during the winter,” Kelaidis explains. Come summer they are ready for a rest before beginning the process all over again.

—Mary Lynn Bruny

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