In Search of Tropical Gentians

Gentians need no introduction to most people interested in plants. Several species, particularly the Fringed Gentian (Gen- tianopsis cninita), are among the most beautiful and avidly sought-after wildflowers in the eastern United States. Others, mostly alpine and subalpine species of the Old World such as Gentiana acaulis, G. scabra, and G. septemfida, are becoming increasingly popular as rock garden subjects. But the Gentian Family, or Gentianaceae, includes a diverse group of plants, many of which are unfamiliar to the layman and probably would not be recognized by him as gentians. This is particu- larly true of those members of the family that are native to the American tropics. While the gentians (in this article, the term "gentian" will refer to any member of the family) of the North Temperate Zone are entirely herbaceous, many tropical species are shrubs or even small trees. My interest in tropical gentians began while I was a graduate student at Duke University; and it has continued, giving me an opportunity to travel to various parts of the American tropics. In this article I will recount some of my impressions and ex- periences of these travels, as well as discuss a few of the gen- era with which I came into contact. My thesis research was concerned with the genus Lisianthius, which includes 27 species distributed in Mexico, Central Ameri- ca, and the Greater Antilles. Plants of this genus are herbs, shrubs, or small trees with flowers to 2 1/2 inches long, usually bright yellow in color. A few of the species have red or greenish flowers, but the most extraordinary one, aptly named Lisian- thius nigrescens, or Flor del Muerte (Flower of Death) in its na- tive Mexico, has flowers that are very nearly black. In certain light, a slight reddish tinge may be observed, but these are the blackest of any flowers I have ever seen. My first trip in search of Lisianthius took me to the island of Jamaica, with my sister, Sylvia, as a companion. This was my first experience with a tropical flora, and the variety of un- familiar plants was quite bewildering; but it was a successful trip. We had unlimited (and free) use of a Land Rover, with which we were able to travel over much of the island, and I 189 190 was able to collect all eight of the Jamaican species. This is not as impressive a feat as it sounds, since most of the species are found along roadsides. One of them, Lisianthius longifolius, locally called the Jamaican Fuchsia (although it resembles a Fuchsia only in the shape of its flowers, and then only vaguely) is common and conspicuous, and both my sister and I became adept at spotting it while speeding along at 50 mph. or ne- gotiating the frequent hairpin curves on the tortuous mountain roads. During my travels through Mexico and Central America in search of Lisianthius, I have come across several other gentians, perhaps the most noteworthy of which are the species of Voyria. These delicate plants, seldom more than 6 inches tall and with the leaves reduced to inconspicuous scales, are without chloro- phyll and therefore unable to manufacture their own food. They must obtain their nourishment from other plants, either living or dead. Most species have flowers 1/4 to 1/2 inch across, but some are much larger; the color varies from white through pink, purple, and yellow. I first saw these plants in the dense forests of Barro Colorado Island, a natural preserve in the middle of the Panama Canal maintained by the Smithsonian Institution. The field station for visiting scientists has comfortable accommodations, and, most welcome in the steamy climate of sea-level Panama, an air-conditioned laboratory. But it is the animals that are per- haps Barro Colorado’s most spectacular feature. Nowhere else in Central America can such a variety of wild mammals be seen under such favorable circumstances. Three species of monkeys - Capuchins or White-faced, Spiders, and Howlers - are conspicuous, the last particularly so because of the loud booming calls of the males. Sloths and Tamanduas (a kind of arboreal anteater) are frequently seen in the trees close by the station, and coati-mundis, peccaries, and even a tapir came by for handouts. Although there are a number of interesting and beautiful species of Gentianaceae in Central America, there are many more in South America. In fact there are probably more species of gentians on that continent than on any other. I had my first look at South America in the fall of 1968, when I spent three days in Colombia. I had little time to sightsee, but I did have an opportunity to visit the high elevation vegetation, or paramo, some of which is accessible by cable-car from Bogota. I saw enough to want very much to return. I had my chance four years later when a collecting trip took me back to Colombia, as well as to Venezuela and Peru. Gentianella nevadensis (above) and Gentiana sedifolia (below), both twice life size. These photographs illustrate one of the primary differences be- tween the two genera. Gentiana has an extra fold between each of the corolla lobes, in the case of this species at least, giving the appearance of having ten "petals". These folds are absent in Gentianella. Photo R. Weaver. 192

The term "paramo" is used to denote a vegetation type that is peculiar to the Andes of Venezuela, Colombia, and Ecuador between 10,000 and 15,000 ft. elevation. Although in their lower reaches patches of paramo are often interspersed with stunted trees, the upper levels are truly alpine; rain and fog are frequent, and the temperature usually hovers near the freezing point at night. The most characteristic plants of the paramos are the Espeletias (or "frailejones" to the natives), members of the Compositae, the same family that includes daisies, dandelions, and sunflowers. There are many species, with various habits of growth, but the most common ones are characterized by a dense rosette of silvery or whitish leaves which is often 2 feet across. As the plants grow older, the stem elongates and the rosette is borne above the ground, sometimes to a height of 5 feet or more, with the old, dead leaves hanging down like a skirt. The "flowers" or heads, borne singly or in clusters, arise from the rosette on long stalks. In a landscape dominated by Espeletias, especially in the fog-filtered sunlight so characteristic of these areas, the aspect is almost unearthly. Paramos are delightful places for a botanist. Besides the Espeletias, many other plants are present, some of them "belly plants" (best observed by lying on one’s belly), and others with large, brightly colored flowers. Many of the genera - Lupinus, Senecio, Bidens, Aster, Oxalis, Cerastium, Draba, etc. - are familiar to us from the North Temperate zone. Others of course are primarily Andean, such as the beautiful, azalea-like Befaria, and Bomarea, an Amaryllidaceae with red and yellow flowers that often grows as a vine. I had the good fortune during my trip in the fall of 1972 to be able to stay with a friend, a roommate from my graduate student days, who was studying Espeletias. Our cottage, at 11,500 feet right in the middle of the paramos, was about 30 miles west by good road from Merida, Venezuela. I have never stayed at a more delightful place. Set beside a subalpine lake, full of trout with Blue-winged Teal dabbling in the reeds, with dandelions and white clover by the doorstep, it was overlooked by a snow-covered mountain with a waterfall cascading down its slopes, and surrounded by miles and miles of Espeletia- dotted paramo. The mixture of things familiar and unfamiliar was indescribably beautiful by day or night, in sunshine or rain. Three genera of gentians are common and conspicuous in the paramos. Gentiana sedifolia is the only member of its ge- nus in the Andes. It is a diminutive plant, often indistinguish- Pnrnnzo surroundzxzg Laguna Mucubnyi at 11,500 feet in the Andes of Venezuela. The conspicuous whitish plants are Espeletia schultzil. Photo: R. Weaver.

able from the mosses among which it grows unless its flowers are open. This is truly one of the gems of the paramo. The flowers are about 1/2 inch across and of a brilliant sky-blue color; as is common in this genus, pure white variants are oc- casionally found. Many gentian flowers are sentitive to changes in light and/or temperature, but those of this species are par- ticularly so. Even a cloud passing over the sun will cause them to close. In contrast to Gentiana, perhaps 300 species of Gentianella are native to the Andes. Each high mountain seems to have its own species, and the range of flower color and form is in- credible. A common type, exemplified by G. nevadensis, the most familiar species of the Venezuelan Andes, has flowers which are white to pale lilac with dark purple veins. Those of other species are pure white, purple, yellow, orange, or red. The third genus of the paramos is Halenia. Like Gentiana Symbolanthus tricolor (life size), photographed near Bogota, Colombia; a shrub to five feet tall with beautiful rose-pink flowers. Photo: R. Weaver. 195 and Gentianella, it is widespread in other parts of the world. A number of species occur in the mountains through Central America and Mexico into the southwestern United States; and H. deflexa is found in the north central and northeastern parts of our country and adjacent Canada. In addition, a few species are Eurasian. Halenia is unique among gentians in having four usually conspicuous spurs at the base of the corolla. Other- wise the flowers of most species are not particularly noteworthy, often being as green as the leaves. Immediately below the paramo and grading into it is a forest type variously known as cloud, mossy, or elfin forest, or, unro- mantically, subalpine scrub. The trees here are low in stature with gnarled branches, and they are often heavily covered with epiphytes, particularly mosses, liverworts, and lichens; all these attributes are probably a direct response to the very frequent fog. This forest type occurs at higher elevations throughout tropical America, and although the plant species may change from place to place, the aspect remains much the same. Three genera of gentians are characteristically found in the elfin forests. The largest of these, both in the number of species and the stature of the individual plants, is Macrocarpaea. There are perhaps 50 species, of which a third remain to be scientifi- cally described. These plants are usually small trees, up to 15 feet tall, with large glossy leaves, and pale yellow or green- ish flowers as much as 3 inches long and 2 1/2 inches across. Although the color of the flowers is not outstanding, their large size and the profusion in which they are borne produce a spectacular display when the plants are in full bloom. In many species I noticed that a rather large percentage of the flowers appeared to have been torn open by something. This was quite a mystery until I realized these plants are prob- ably pollinated largely by bats. These creatures, in search of nectar, are notoriously rough on the flowers from which they get their snacks. I have collected 10 species of Macrocarpaea, from Jamaica to southern Colombia, but perhaps the one I remember most vivid- ly is a rather ordinary looking one from Venezuela. When I found it, I recognized at once that it was a species new to sci- ence - which was exciting - but almost immediately my at- tention was drawn to a movement on the ground nearby. The stream by which the plant was growing was literally crawling with dozens of the most extraordinary frogs. These creatures were sluggish and easy to catch - unusual enough for a frog

Macrocarpaea pachyphylla (114 life size), one of a genus of shrubs com- mon in high elevation forests in the Greater Antilles, Central America, and northern South America. Photo: R. Weaver. 196

- but their color, lemon yellow with ruby eyes, was their most startling attribute. How I wished that I could have taken a few home for my vivarium. In the lower parts of the elfin forest, another gentian is to be found. Plants of the genus Symbolanthus are usually shrubs less than 5 feet tall, and the flowers of many species are truly beautiful. Up to 5 inches long and a delicate rose-pink with white lines on the inside of the corolla lobes, they are not easily overlooked. They are unfortunately scentless, as are most of the family. Still another shrubby gentian of these forests, but only in that part of the Andes near the Colombia-Venezuela border, is Lagenanthus princeps. This plant has been called the "prince of the gentians" and deservedly so. The tubular flowers are 6 to 7 inches long, bright red at the base, changing to yellow in the middle, and finally lime green at the tips. Although I have seen flowers that are more beautiful, I have seen few that are more spectacular. As one travels through the tropics (or any- where else for that matter), one finds that the plants grown ornamentally are seldom natives of the area; in fact roses and geraniums are far from uncommon. It is thus a tribute to the beauty of Lagenanthus princeps that people in the area where it is native often grow it beside their homes. The lowlands of South America are poor in gentians. The most conspicuous genus is Chelonanthus, and one of these, C. alatus, a weedy plant of roadsides and cut-over fields, is the most common and widespread species of the American tropics. Unfortunately it is also the least attractive. The plants are tall and coarse and the flowers are green and inconspicuous. It does have a redeeming quality, however; according to Dr. Bas- sett Maguire of the New York Botanical Garden, the Indians of Guyana boil it up and use the extract to make a glaze for their pottery. Several of the more spectacular tropical gentians have been grown as greenhouse plants. Lisianthius longifolius was culti- vated in England as early as 1793, and several species such as Purdieanthus pulcher, a beautiful red-flowered shrub, were first described from cultivated material. But most species gradually disappeared from cultivation, although Lisianthius nigrescens is still reportedly grown in the Royal Botanic Gardens at Kew. I have grown various species of Lisianthius for several years, both in the greenhouses of Duke University and here at the Arnold Arboretum. Cultural requirements are relatively simple for these plants. The seeds germinate after about a month

Lisianthius nigrescens (1 1/2 ttmes life szze), a rather weedy plant whose nearly blach flowers are a common sight along the Interamerican High- way in southern Mexzco. Photo: R. Weaver. Chelonanthus alatus (life size), a common weedy plant along roadsides in Central America and northern South America. Photo: R. Weaver. Halenia asclepiadea (life size), showing the spurs at the base of the flowers that set this genus apart from all other gentians. Photo. R. Weaver.

and the seedlings grow slowly during their first year. After that growth is rapid, and most species have flowered by the end of the second year. They are not fussy about soil, but they appear to do best with a periodic sprinkling of lime. Although the flowers and foliage of most species are attractive, Lisian- thius can hardly be recommended as a good greenhouse sub- ject. The plants get to be quite coarse and leggy, assuming a most ungraceful appearance after several years. However, be- cause of the unusual color of its flowers, some people might consider Lisianthius nigrescens to be worth the trouble. Sev- eral members of my family have grown these plants on window ledges in their homes, with varying degrees of success. I have hybridized several of the species, but to date, none of the resulting progeny has proved more satisfactory horticul- turally than both of the parents. Second generation hybrids are being grown at present, though none has reached maturity. Although the South American species of Halenia and Gen- tianella are primarily plants of alpine areas, temperatures in their native habitats seldom drop more than a few degrees be- low freezing. Therefore they would doubtless prove tender in most parts of the United States. I have seedlings of a number of species, but they will be grown indoors. The flowers of Lagerzantlzus princeps and several of the Sym- bolanthus species are so spectacular that, in my opinion at least, these plants are worthy of cultivation no matter how ungainly they might grow to be. I brought seeds of both genera from South America. However, judging from conditions in their native habitat, and from the experience of the British more than a century ago, a cool greenhouse will be needed to raise them to maturity. RICHARD E. WEAVER