On numerous occasions, folks have inquired about a lovely looking orchid growing along some of our highways. Upon investigation, we find that the orchid in question is most often the bamboo orchid, Arundina graminifolia. Its name is descriptive of its canelike stems and grassy leaves.

The bamboo orchid is the lone member of the genus Arundina. Native to tropical Asia and some of the Pacific islands, it also has been introduced to Puerto Rico and Central America. Along with the spathoglottis orchid, it is believed to have been spread to the Ko'olau Mountains in the 1930s when the Hawai'i sugar planters were reforesting our watershed areas. As the trees were planted, the bamboo orchids caught a free ride in the pots of the trees and subsequently established themselves in our tropical climate.

The Arundina is a terrestrial orchid with canelike stems, which if left undisturbed, could form large clumps, thus giving it an appearance of a clump of bamboo. It is often seen in sunny areas on the forest fringe or in disturbed areas such as road cuts.

The orchid often starts blooming when the plant stalks are two to three inches tall, and mature plants can be more than six feet tall, with alternating lance-shaped leaves and flowers emerging from the apex of the stems.

Blooming season usually runs summer through fall, but a mature plant could flower nearly all year long. The fragrant flowers are two to three inches across and are normally a rosy lilac to mauve in color, with a darker purple lip, giving the flowers the appearance of a miniature cattleya. There is even reported a semi-alba (white with purple lip) form, but after seeing thousands of plants, I have yet to see a true semi-alba.

Flowers last up to three days and open consecutively, thus extending the flowering season, but plants rarely allow more than one flower to be open at the same time.

Occasionally, viable seed pods will form, producing millions of white powdery seeds. These seeds get caught up in the wind and can be transported for miles. This orchid is now found on all of the main Hawaiian Islands. Even though the seeds germinate readily, it is not considered an invasive species, at least for now.

After flowering on the end of the stems, side shoots or keiki will appear. As they grow, their weight may allow the stems to reach the ground, thus providing another method of propagation.

Give the bamboo orchid full sun (in mauka areas) and partial sunlight in the hotter leeward areas. They like an abundance of moisture but also require good drainage. A mixture of black cinders and peat moss is a good amendment for planting in the ground. The orchid also will take well to potted culture.

Propagation normally is done by digging clumps of the rhizomes. These establish fairly quickly and could flower within a year. Keiki can also be planted but will take longer to flower. Fertilize with any balanced formula water-soluble or timed-released fertilizer.

The bamboo orchid is a welcome addition to our tropical landscaping. Large mature clumps can bring spectacular results, blooming for several months, with very little care. Few plants can offer so much reward for such little effort.

Scot Mitamura is an orchid horticulturist for the Honolulu botanical gardens. Reach him at hbg@honolulu.gov.