Fig. 1 Air plants on powerlines

Fig. 1 Air plants on powerlines

Growing on Air?

We know that plants and animals adapt to their habitats with survival features or behaviors that make life possible in many habitats, from deserts to the arctic. Yet, air plants (Tillandsia) are amazing flowering plants (angiosperms) that live without their roots anchored in soil!

As a tourist in Costa Rica, I kept looking upwards hoping to see a three-toed sloth hanging from a tree branch or a powerline. However, in looking for sloths, I was more likely to see air plants attached to powerlines (Fig. 1). How can a plant survive in such a habitat?

The genus Tillandsia in Bromeliaceae (Pineapple family) includes several hundred species of evergreen, perennial, flowering plants. They are epiphytes, meaning “upon a plant” in Greek. They attach to a substrate, commonly a tree or a rock and also powerlines, but derive no nutrition from the substrate (i.e. they are not parasites). Tillandsia and about half of all known orchids grow epiphytically on “perches” that give them access to light. Tillandsia species are native from the South-Eastern U.S., Mexico, Central America, Caribbean Islands to Central Argentina and are found in many habitats, including forests, mountains, and deserts.

How Air Plants Got Their Generic Name

Erik Tillander (1640-1693) was born in Sweden about 70 years before Linnaeus. He studied botany and medicine at the University of Uppsala, Sweden and the Academy of Turku, Finland. He got his doctorate in Holland in 1670 and shortly thereafter became Professor of Medicine in the Academy of Turku. When Tillander was a student, he got so seasick in a violent storm on a voyage from Turku to Uppsala that he never traveled by boat again. He returned to Turku by walking around the Gulf of Bothnia (northern part of the Baltic Sea), a distance of about 1000 miles. It has been said that he changed his name to Elias Tillandz (‘till lands’ means ‘by land’ in Swedish).

Many decades later, Linnaeus honored the memory of his fellow Uppsala alumni by naming a large genus of American plants capable of growing away from water Tilllandsia after Professor Tillandz because of his fear of water. Linnaeus was known for naming plants to celebrate botanists as well as to insult those that he had quarreled with.

Fig. 2 Cardinal air plant (Tillandsia fasciculata) with broad leaf bases By Usien

Fig. 2 Cardinal air plant (Tillandsia fasciculata) with broad leaf bases By Usien

Some Morphology, Anatomy and Physiology

Air plants have no true roots, but rather a “holdfast” allowing the plant to hold on to a substrate. Water and nutrients must come from the surrounding air, rain, or fog and are absorbed by the leaves instead of through a root system. Some species have a compressed stem axis so that the rosettes of leaves are close together. The bases of the leaves are often flared, overlapping with each other, and forming a funnel or cup that collects and holds rainwater (Fig. 2). The leaves of other air plants hang loosely from their aerial perches (Figs. 3a & 3b).

Scale-like trichomes, minute outgrowths of the epidermis on the leaves, absorb water that is used by the plant in various processes, including photosynthesis. Nutrients in the form of dust are also taken into the leaf by trichomes. Decomposed debris from the surrounding air can accumulate around leaf bases, where it is absorbed by these minute epidermal outgrowths.

Recent studies have shown that in many epiphytic species, bacteria play a great role in fixing atmospheric nitrogen. Tillandsia recurvata (Fig. 3a), a widespread species in North and South America, has been shown to have its leaf surfaces covered by nitrogen-fixing bacteria. Nitrogen-fixing bacteria in root-nodules that produce ammonia and nitrates used by the host plants is common in Fabaceae (the Pea family which includes beans, peas, lupines, and brooms).

Fig. 3a Small ballmoss (Tillandsia recurvata) By Juan Carlos Fonseca Mata Wikipedia

Fig. 3a Small ballmoss (Tillandsia recurvata) By Juan Carlos Fonseca Mata Wikipedia

Fig. 3b Tillandsia sp. By Eva Buxton

Fig. 3b Tillandsia sp. By Eva Buxton

Fig. 4 Blushing bride -Tillandsia ionantha Mokkie

Fig. 4 Blushing bride (Tillandsia ionantha) in bloom with reddish foliage By Mokkie

The flowers are showy in some Tillandsia species (Fig. 4) and inconspicuous in others. The foliage can vary from green to a white, silvery color, and in some species changes to a bright color when the plant is blooming, helping to attract pollinators such as moths and hummingbirds. The seeds have hair-like appendages, so they can be blown away by the wind. Air plants also reproduce vegetatively by growing offsets called “pups” at the base of the plant.

 

 

 

Fig. 5 Spanish moss (Tillandsia usneoides) Wikipedia

Fig. 5 Spanish moss (Tillandsia usneoides) Wikipedia

Spanish Moss

The lacy-looking, grey “stuff” hanging off trees and shrubs in Marin County and often erroneously referred to as Spanish moss is a lichen in the genus Usnea. (A lichen consists of a fungus and an alga in a symbiotic relationship.) Spanish moss (neither from Spain, nor a moss) is an air plant in the genus Tillandsia. Its specific epithet is usneoides (oides means “look like”) because it resembles the lichen Usnea.  My first encounter with Spanish moss (Tillandsia usneoides) (Fig. 5) was in Jacksonville, FL, where it was hanging from the most magnificent oak I have ever seen, a Southern live oak (Quercus virginiana).

Santa gave me a Tillandsia juncea with a flowering stalk. I can’t wait for it to bloom!

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