Native bulbs:  Unappreciated garden gems

 

By Jeanne Frett, Research Horticulturist, Mt. Cuba Center

 

Mention the word “bulb” and most people conjure up images of spring displays of  tulips, hyacinths or daffodils which are all native to Eurasia, the Mediterranean region or northern Europe. However, eastern North America is home to a number of unique, beautiful, and easy-to-grow waiting to be discovered.  While most are not as widely known or cultivated, they are highly desirable for the garden.

One of our projects at Mt. Cuba Center has been to grow native bulbs to evaluate them for their ornamental qualities, hardiness, and adaptability to garden culture. If they are not available commercially, we grow them from seeds, a process that typically takes from two to five years.  Fortunately, a growing interest in native plants promises to insure wider availability of native bulbs for gardeners as well. 

So, what exactly is a bulb?  A bulb is defined as a modified underground stem with a bud and thickened fleshy scales that contain stored food.  Bulbs typically have a period of dormancy during which time they remain below ground; when conditions are right they produce stems and flowers.

Onions and scallions are examples of bulbs that are used for their culinary attributes. The nodding wild onion (Allium cernuum) is an ornamental species that has an elongated bulb, similar in shape to scallions.  From late June to mid-July, flat-topped flower heads, or umbels, of pink, purple or pinkish-white flowers are produced on 12-18” stalks.  We grow nodding wild onions informally in our meadow among ornamental grasses where they produce a pink haze of color in mid-summer. They are easily grown, not aggressive, and perform well in full sun to part shade in well-drained soils of average fertility.

The western North American species of camass or wild hyacinth are fairly easy to find in gardens and bulb catalogs, but eastern camass, (Camassia scilloides) requires additional searching.  However, once you’ve seen the icy blue, slightly fragrant, star-shaped flowers borne in loose upright flower stalks to 18” tall, you’ll be convinced that they’re worth a try.  They flower from early to mid-May.  The narrow, sword-shaped foliage emerges with the flowers and persists for a month or more before becoming dormant.  We grow our plants in the woodland garden in partial shade and also in full sun. The plants need moderately moist soil in spring but, once dormant, will tolerate drier conditions.

Spider lily (Hymenocallis caroliniana) is a rather exotic, tropical-looking plant but the northern limit of its natural distribution is Illinois and Indiana and reliably hardy to Zone 6. It is not a true lily but a member of the Amaryllis family. The large, fragrant flowers are grouped 2 to 7 in a cluster on a 2 to 2½’ tall leafless stalk.  Above a ring of six white straps is a flaring cup of tissue resembling a white morning glory. Although spider lilies grow naturally in moist to wet conditions, we have successfully grown them in average soil, watered during drought, in full sun and part shade. Our plants produce numerous green olive-like seeds that germinate slowly over a 6 month period and provide a ready source of additional plants for the garden.

The Turk’s cap lily (Lilium superbum) is easily grown in moist, well-drained soils in full sun to partial shade but is infrequently seen in gardens. It is an impressive plant, growing 4 to 8’ tall with leaves arranged in whorls around the stem. Large clusters of nodding orange flowers with sharply reflexed petals and greenish, densely maroon spotted throats appear in late July. The plants often spread slowly to form impressive colonies. Other native lilies growing in the gardens at Mt. Cuba Center include the Canada lily (Lilium canadense) with yellow, orange, and red flowers as well as the drought tolerant Carolina lily (Lilium michauxii) which resembles a shorter version of the Turk’s cap lily.

Many gardeners are familiar with the name oxalis or wood sorrel as the nasty weed in their lawns or fields.  However, violet wood sorrel (Oxalis violacea), a dainty 4 to 8” tall woodland species, deserves a place in the garden. It has typical clover-like leaves and 3 to 6 rosy- purple flowers on each stem in May and again in September. Since the leaves die back towards the end of summer, these late flowers often appear without foliage. Violet wood sorrel is best grown in moist, well-drained soils in sun to dappled shade.  Try adding them to your rock garden or small, intimate area where they can be appreciated up close. 

Atamasco lily, Zephyranthes atamasco is listed as marginally hardy in this geographic area (recommended for USDA hardiness zones 7-10), however, we have grown it successfully at Mt. Cuba Center for a number of years.  It is certainly worth a try outdoors in our region of the U.S.  Contrary to its common name, Atamasco lily is not a true lily but a member of the Amaryllis family. The white, solitary, funnel-shaped flowers appear in early May on 8 to15” stems and change from white to pink as they age. It is easy to grow in full sun or partial shade in moist soils and is most effective when used in masses to form drifts.

Needless to say, from this short list of native bulbs, there is a wide array of these beauties waiting to be explored. There’s no doubt they can add beauty and seasonal interest in your garden if you’ll make the effort to search for them.  Consider adding several of these gems to your garden and impress your friends with your sophisticated knowledge of native bulbs.   You won’t be sorry.

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The internet is a good place to find sources of native bulbs.  If the bulbs are unavailable in the spring, try searching again in early fall, which is an ideal season to plant. Be sure to get started soon and investigate the possibilities of gardening with native bulbs.

To get started with native bulbs, a few sources to get started include:  www.native-gardens.com; www.nearlynativenursery.com; www.prairiemoon.com

Nodding wild onions (Allium cernuum) are not aggressive and make carefree additions to the flower border, meadow or wild garden

Eastern camass (Camassia scilloides) flowers start opening from the bottom and work upwards; the pale blue flowers last up to 10 days.

 

Spider lily (Hymenocallis caroliniana) flowers are fragrant and are pollinated by moths in the evening; they remain open through the next day.

Turk’s cap lily (Lilium superbum) is the largest native lily east of the Rocky Mountains and is pollinated primarily by swallowtail butterflies.

Violet wood sorrel (Oxalis violacea) can spread to form colorful colonies of diminutive plants with rosy-purple flowers.

Atamasco lily, Zephyranthes atamasco flowers appear from early to late May and look like small white lilies.