By Michael MacCaskey

Tillandsias, and other members of the Air Plant Database,  do their best work up high. Travel in the southern United States, or Central and South America, and you see them living way up in the trees, sometimes covering entire branches like some kind of vegetative fur. But unlike the basketball star Mr. Jordan, who is simply able to reach great heights, these plants seem to live and grow in nothing but air.

In a sense, they do live on air. Though a few are terrestrial, most tillandsias are epiphytes, a two-bit word that means they use other plants for support. But, as opposed to parasitic plants such as mistletoe, they're respectable guests and don't steal nutrients from their hosts. They have roots, but these serve primarily to hold the plants in place. Tillandsias get all the moisture they need from fog or rainfall, and all the nutrients they need from the dust, leaves, and debris that collect around them.

Tillandsias are a genus of the bromeliad family, the best known of which is the pineapple. Of the approximately 2,000 species of bromeliads, 600 are tillandsias. The best-known tillandsia is Spanish moss (T. usneoides), which is a common sight hanging in lacy strands from live oaks and bald cypresses throughout the Gulf Coast region.

There are two main types of tillandsias, and it's easy to distinguish them: some are gray or mostly so, and some are green.

The gray kinds grow naturally in tropical forests where long droughts are common. Their gray leaves reflect sunlight, conserving moisture in the leaves and so helping the plants survive. Green-leaved tillandsias are native to rainy, humid tropical forests. You can grow either indoors, but our homes (and the care most gardeners give) more closely approximate the dry tropics than the humid tropics, so gray kinds are a better bet indoors.

Displaying Tillandsias
As with most plants, imitating their natural environment is the best way to display tillandsias. That means attaching them to trees outdoors (if you live where winters are frostless, USDA Hardiness Zones 10 and 11), or on branches, driftwood, slabs of bark, or similar material indoors.

The key to establishing a tillandsia on a piece of wood is to secure it firmly in place until its roots can reach out to the tree or mount and attach themselves. You must take care that the plant is firmly secured and not wobbly. Use wire ties, narrow-gauge wire, monofilament fishing line, or adhesive, whichever you find easiest to use and best adapted to the plant and support you're using. Our favorite tool is hot glue. Tillandsia specialist Paul Isley, owner of Rainforest Flora in Los Angeles, uses a ready-to-use adhesive, Tilly Tacker. Don't use epoxy or petroleum-based glues; they may harm the plants.

Once you've selected the mounting material, experiment with different placements for your plants to see if you like the look. Don't situate plants in deep pockets where water will collect, and where light and air movement are blocked. Standing water around leaves causes the plant to rot. Trim long roots to make mounting easier. Small, stemless plants are easy to glue directly to the smooth surface of a branch. Narrow drill holes are also suitable for plants with particularly narrow bases, such as T. purpurea. In either case, apply hot glue or other adhesive directly onto the surface or in the hole of the mounting material, and put the plant into it. If you use hot glue, let the glue cool for 20 seconds or so before putting the plant into it.

Caring for Tillandsias
In winter, plants need bright light, good air circulation, and once-a-week watering. In summer, provide filtered bright light and more frequent watering, as well as monthly fertilizing with a liquid product at quarter-strength.

Your maintenance regime depends partly upon how you display your plants. If they're mounted or positioned so they're not easy to move, mist the plants with a spray bottle. If they are not attached to a mount, immerse the entire plant in water for up to 12 hours every other week or so.

In frost-free areas, tillandsias can grow outdoors all year. Start by attaching them to the branches of trees. They'll soon adapt, requiring no additional care, and will eventually spread.

Propagate tillandsias by separating offsets that are a third the size of the mother plant. Use a knife or pruning shears if they don't pull apart readily.

Some Tillandsia Favorites
Of the hundreds of species of tillandsias, here are some of the ones you are most likely to encounter in nurseries or by mail order:

T. aeranthos has 4-inch-long scaly, lance-shaped gray leaves. Dark blue flowers (surrounded by rose pink bracts) appear in spring on cylindrical spikes. It's found growing in trees in Argentina, and is more tolerant of low humidity than most.

T. bergeri has narrow, triangular, and scaly leaves about 2-1/2 inches long. Blue and white flowers that fade to rose pink come in spring. This plant is found closer to the ground, growing among rocks in one mountain range in Argentina. It grows into a clump faster than any other tillandsia, and produces offsets year-round. Bright light is required for optimum growth.

T. cyanea has 8-inch triangular dark green leaves that emerge from a central rosette. They show a characteristic red stripe near their base. The bright pink paddle-shaped flower spikes produce solid dark blue or violet flowers. T. cyanea is easy to propagate and is often sold as a potted plant. The native range of this plant is centered in Ecuador. A popular hybrid with T. lindenii is 'Emily', which has clove-scented flowers.

T. ionantha is one of the most common and robust tillandsias. It produces numerous 1-1/2-inch curved leaves in dense rosettes. It's often grown unmounted and hung by only a wire or monofilament line. Normally, leaves are gray green, but they turn red before flowering in late spring, especially toward the center of the plant. Flowers are blue, purple, red, and even white, while its bracts are white. Many named varieties are available. It is common in Nicaragua and western Mexico.

T. purpurea grows in a rosette with leaves up to a foot long spiraling around the center. Each 4- to 6-inch-long leaf is gray, triangular, and tapered. Flower spikes are about 6 inches tall and produce very fragrant white flowers with purple edges that are surrounded by lavender to purple bracts. It's native to Peru.

Michael MacCaskey is a former editorial director at National Gardening.

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