The prominent 19th century English botanist, Francis Kingdon-Ward, wrote manuscripts in great detail profiling his lifelong collection of high-altitude ornamental plants. Throughout his lifetime, Kingdon-Ward scavenged the Namcha Barwa Mountain crevices and the Tsangpo River Gorge for these select alpine plants during his some 65 explorations through the southeast of Tibet. These rare plants became the gems of his world-famous collection and ultimately, became his lasting legacy. Perhaps, the modern gardener's intrigue for alpine plants can be traced back to Kingdon-Ward's evocative descriptions of these beautifully rare plants. In any case, the botanical world has developed a great fascination for these charming ornamentals. Our fascination is firmly rooted in the marvel of botanical life that is capable of inhabiting and thriving on the so-called "Rooftop of the World."
The alpine biome can be a place of great reward for those interested in ornamental plants. Alpine biomes are found in mountain ranges all around the world and are frequently defined by altitudes of 5000 meters or more above sea level; spatially, they lie just below the perpetual snow line of a mountain. In Latin, a translation for "high mountain" is alps. From this translation, we've derived today's colloquial term alpine.
Mountains and their influence on localized climates often give rise to a greater diversity of plant habitats and species than can be found in similar regions at lower elevations. The North American Rocky Mountains show great ecological diversity beginning with a desert biome. As you climb to higher elevations, desert evolves into a deciduous forest biome, then a grassland biome, a steppe biome, and finally, the harsh and cold sub-alpine and alpine biomes. The alpine environments are characterized by thin air, dramatically increased ultraviolet radiation, damaging wind speeds, erratic precipitation including snow cover, predation, and sharp soils with unique profiles and low fertility. These unique environmental factors have led to the evolution of particular plant adaptive traits most commonly associated with the alpine species capable of inhabiting these dynamic environments.
In all high mountains, the parent rock has been eroded away through time. Appalling disasters can accompany these natural forces of erosion and gravity. These disasters cannot be controlled. Much of this erosion occurs unnoticed during the monsoon rains in the Himalayas, or as the rocks become detached following many freeze-thaw cycles in the Teton ranges of Wyoming. The most visible erosion contributors are the glaciers and snowfields found on these mountain ranges. Since the onset of the first Ice Age, nearly two million years ago, ice has constantly reshaped and changed the world's alpine biomes. With the changing environment, plant species have been forced to make similar adaptations. These changes have resulted in interesting growth forms and distinct morphological features that allow specialized plant species to survive and thrive where others would perish.
Ecological biomes are distinguished, in part, by their relative altitudes above sea level. In the Himalayas, distinct vegetation zones are home to numerous species of flora from the subtropical, temperate, subalpine, and alpine biomes. Because of the severe climate of the alpine biomes across the world, plants have developed adaptive traits specific to these conditions. Though there are only approximately 200 species of true alpines (sp. found at altitudes eclipsing 5000m), this exclusive plant group offers much novelty and charm for its unique role in these select environments.
Above, a low growing, "mat-form" moss campion species from the Grand Teton demonstrates an interesting adaptive technique required for life cycles at these altitudes. Because of the cold and wind, most alpine species are small perennial groundcover plants that grow and reproduce slowly. They protect themselves from the desiccation and damage of wind and cold by hugging the ground and growing over parent rock, which can serve temporally to radiate collected heat and offset decreases in ambient air temperature. At high elevations, adaptation becomes a balancing act; this act can shift course dramatically and without warning. At alpine elevations, there are reduced levels of atmospheric carbon dioxide. There are high winds and biting cold. Precipitation levels vary greatly. The temperature of an alpine zone can change from temperate to freezing in one day. These environmental factors influence metabolic processes that determine a plants life cycle. Flora from these elevations is challenged greatly by damaging ultraviolet radiation levels. Along with novel morphological growth forms, other unique adaptive traits signify the specialization of alpine plants and allow them to thrive in these harsh conditions.
The arctic willow, from the family Salicaceae, is a charming alpine when in bloom. This willow species is uniquely adapted to survive in harsh arctic and sub arctic environments and has an indigenous distribution surrounding the Arctic Ocean. It grows natively in tundra and rocky moorland and is the northern-most woody perennial plant in the world. Salix artica is a particularly beautiful, low-growing shrub, which, amazingly, grows to a maximum height of six inches. As you can see in this photograph, the foliage is coarsely pubescent (hairy). Pubescence is a common morphological feature in alpine plants. This specialized plant trait serves a number of important functions for alpine plants including:
- Hairs on plants growing in areas subject to frost keep the frost away from the living surface cells.
- In windy locations, hairs break-up the flow of air across the plant surface, reducing desiccation.
- Dense coatings of hairs reflect solar radiation, protecting the more delicate tissues underneath in hot, dry, open habitats.
- In locations where much of the available moisture comes from cloud drip, hairs appear to enhance the uptake process.
At 4200 meters, the texture of this landscape looks a bit different. In Peru, indigenous cacti, such as Mammilaria sp., dominate higher altitudes. The adaptive traits remain the same though- stiff, bristly trichomes, spines, and hairs.
In addition to protecting these plants from unnecessary water loss and light damage, these trichomes and spines help discourage scavenging animals from eating the plants. Animal diversity in the Alpine biome is as broad as plant diversity and warrants a plant's protective measures against predation.
Familiar ornamental genera are well represented in the wild by alpine species that display many of the same beautiful characteristics from each respective genus. Kalmia microphylla is one such representative species. Kalmias in the landscape are cherished for their colorful, energetic blooms through the summer. In the case of K. microphylla, this charm is further magnified by the plant's miniscule mature height of between 5 and 20cm tall. The flowers, while abundant, are between 5 and 12 mm in diameter (average .47 inches). K. microphylla is a wildly variable species, known to grow on wet, boggy soils and dry moorland alike. The diverse distribution range of K. microphylla serves to illustrate the dynamic qualities of highly variable alpine environments. Adaptation is required of each species in order to survive.
Although alpine plants natively inhabit mountainous peaks in the far-off wild, they have a deserved spot in our home gardens for their brilliance and charm. In special cases, traditional alpine genera have transcended the realm of academic botanical monographs and become major players and features in our ornamental gardens. The genus Primula has strong roots in both alpine biomes and ornamental gardens alike. This highly variable, but universally captivating group of plants frequently serves as one's first introduction to alpine ornamentals. Primulas capture many of the ornamental qualities that make alpine plants so desirable and captivating. There could be no better first introduction.
In total, alpine plants offer great charm and wonder for the world of ornamentals. Amongst the lore and excitement surrounding ornamental alpine plants, one gleaming interest point captivates: Few have scaled the world to these "roof-top" alpine heights, sometimes in excess of 16,400 ft above sea level, to see these specialized plants in their native habitat. Few know that these plants exist and thrive in a place so diverse and so harsh, it cannot be helped but to marvel at Mother Nature's secret world atop vast mountains.Truly, little could compare with scaling the face of a mountain to 5,000 meters in search of botanical life. Quite some time ago, Francis Kingdon-Ward searched the world over for these special flowers and their respective pollinators and found a natural world as breathtaking as the thin air that surrounded him.