All the plants of a given country are at war one with another. The first who establish themselves by chance in a particular spot tend, by the mere occupancy of space, to exclude other species—the greater choke the smaller, the longest-lived replace those which last for a shorter period, the more prolific gradually make themselves masters of the ground, which species multiplying more slowly would otherwise fill.
Augustin Pyramus de Candolle 1820
Writing more than a decade before Charles Darwin embarked on the Beagle, Swiss botanist Augustin Pyramus de Candolle (1778–1841) foreshadowed the idea of the survival of the fittest when he wrote of the ecological competition between plants, a competition with inevitable winners and losers. Over geological history, the groups of plants that cloak the earth have shifted dramatically with changes in climate, and as new groups of plants evolved and entered the battle for territorial supremacy. Between the Devonian and early Cretaceous periods (about 380 to 125 million years before present), the world’s flora saw the rise and dominance of gymnosperms: conifers, cycads, ginkgos, and others. In the early Cretaceous, angiosperms, or flowering plants, began to evolve, proliferating into the hundreds of families, now some ninety percent of all plant species, which now dominate vast areas of the planet. Gymnosperms (roughly one percent of extant plant species) surrendered huge expanses of land and were pushed to high altitudes, the boreal region, or into cohabitation with the new “masters of the ground,” flowering plants.
Modern ecologists shun the vivid language of “the war between the plants,” couching this battle in terms like “sequential clade competition” and the “active displacement hypothesis.” But with global warming, the shrinking of the boreal forest and mountaintop refuges will only accelerate the gymnosperms’ loss of territory. This largely human-induced change may be more rapid than any yet withstood by the group.
Ebb and Flow
The largest family in the gymnosperms, Pinaceae, the Pine family, includes 232 species, with 119 described as pines in the genus Pinus. Of these true pines, the IUCN lists nineteen as falling in the most dire categories: vulnerable, endangered, or critically endangered. Pinus has one of the widest natural ranges of any genus of trees on the planet, both in terms of latitudinal distribution and altitudinal distribution, and is also one of the most widely planted of trees. Predominantly native to the Northern Hemisphere, pines grow from 72 degrees North latitude in Siberia to just below the equator in the mountains of Sumatra, and range in elevation from coastal species like Pinus rigida and Pinus banksiana to pines in Mexico and the Himalayas growing well above 10,000 feet elevation.
Still one of the most poorly known pines, Pinus krempfii of Vietnam is also highly unusual. Its broad, flat leaves can measure 12 mm wide over a length of 10 cm, unlike the more familiar thin needles of species like white pine, Pinus strobus. In the tropical forests it inhabits, it grows to be a colossal tree, towering over the surrounding flora. The species was described in 1921 by the French botanist M. Krempf, in the Nha Trang vicinity, where it is no longer found. Never widely collected, its specimens in cultivation number in single digits outside of Vietnam. A tropical holdout in the war of the plants, P. krempfii isn’t faring as well in the competition for collection.
Prior to the discovery of Krempf’s pine, paleobotanists had recorded finds of fossils of a broad-needled Pinaceae. The current climatic conditions where Pinus krempfii is found are warm, humid, and equitable. These conditions prevailed during the Paleocene Epoch (56-66 MYA), during which time a ‘boreotropical flora’ dominated much of the middle latitudes. Gymnosperms such as Glyptostrobus, Sequoia and Taxodium were components of this flora, and, since this epoch, their ranges have been severely contracted. This would have been a period in which P. krempfii or its precursors may have had a far wider range. A diminution of favorable conditions for the boreotropical flora during the Eocene (34-56 MYA), coupled with increasing competition from angiosperms, may have severely reduced the potential range for a conifer adapted to mild conditions. Two fossil discoveries in 2021 in Northern Thailand and Yunnan relate to P. krempfii, and show it once had a greater range. Like Metasequoia glyptostroboides (dawn redwood), it now exists in a highly restricted area. This perhaps adds P. krempfii to the list of “living fossils,” such as dawn redwood and Wollemi pine—plants that were known as fossils before they were linked to extant populations.
Dr. Tim Brodribb, a former Fellow at the Harvard Forest, has visited the wild stands of Pinus krempfii, and his 2008 report with Dr. Taylor Field is to my mind the best recent ecological paper. He argues that Krempf’s pine behaves more like a tropical gymnosperm Podocarpus, noting that the tree “shows photosynthetic, hydraulic and anatomical characteristics more akin to a southern hemisphere podocarp than a pine tree,” with leaves that show a “striking convergence with the flattened leaves of rainforest Podocarpaceae” as well. But what really catches my eye is Brodribb’s profoundly de Candollean view of the species. Krempf’s pine, he notes, offers the first evidence that “Pinus has the physiological (and anatomical) capabilities to invade equatorial evergreen forest. The question remains whether the evolution of broad leaves and shade tolerance is a recent development, representing a new southward invasion of the genus, or alternatively the remnant of an ancient and unsuccessful invasion.” Whether recent or ancient, invasion is a constant.
Collecting for the Smith College Conservatory in the autumn of 1998, I teamed with Dr. Shu-Miaw Chaw of Taipei’s Academy of Sciences to collect rare conifers of Taiwan and Vietnam. We wished to bring into cultivation many rare and endangered species for future research purposes, and Dr. Chaw was to collect DNA samples of conifers for her work on the evolution and phylogeny of gymnosperms. Our research team was to have an extraordinarily successful trip, collecting such rarities as Amentotaxus formosana, Cephalotaxus wilsoniana, Cephalotaxus mannii, Calocedrus macrolepis, Taxus wallichiana, Keteleeria evelyniana, Podocarpus nerifolius—and one of our primary goals, Pinus krempfii.
Once in Hanoi, we began our journey with a courtesy call to Dr. Le Thi Xuan, the head of the Biotechnology Institute, whom we knew from prior collecting trips for Taxus/Taxol research. She had been instrumental in linking us to Dr. Tran Ngoc Ninh, a capable field botanist and expert in the Rubiaceae. As time was tight due to our early flight, we only had time to maneuver quickly through local alleyways to her home and take tea. Our old friend was ill, struggled to move and speak, but insisted on extending hospitality to us. We socialized and exchanged gifts and then briskly headed to the airport for the flight south.
As we were leaving, she pulled me aside. “Be careful in the Đà Lạt Forest,” she whispered. “It is full of danger.”
“What kind of danger?” I replied. “Two-legged or four-legged?”
“Danger of every kind,” she replied, in a grace note worthy of Joseph Conrad.
After two flights from Hanoi, we landed at Đà Lạt airport and drove upward into the hills, where the city lay, at 4900 feet (1500 m), home to over 100,000 people. A balmy summer capital for many of the regimes that have ruled Vietnam, Đà Lạ t boasts a miniature Eiffel Tower as a souvenir of occupation by the French, along with the fine French bread and French roast coffee that can be found in the cafes. At the southern terminus of the Annamite range of mountains, one of the southernmost pieces of high ground on the Asian landmass, a number of conifer genera reach the southernmost extent of their ranges. Isolated here for millions of years, they may possess unusual genetic characteristics.
We stayed at the Biological Institute, located in a former Catholic monastery on the town’s outskirts. It was built by Catholic monks in 1950 but lost to the Communist takeover in 1954. Despite the apparent low budget, the institute had a tissue culture lab and was involved in conserving the many endemic plant and animal species of the region. In the small nursery outside grew a number of conifer species we sought, including Taxus wallichiana, Dacrydium elatum, Fokenia hodginsii, and Podocarpus neriifolius. The former Director of the Arnold Arboretum, Dr. Peter Ashton, who had been to Đà Lạ t, had informed me that a specimen of Pinus krempfii also grew nearby. In Công Ty Park on the outskirts of town, we found a Keteleeria evelyniana in cone, a member of the pine family, which grows well in our southern states but is poorly known horticulturally. No more than fifty feet from it, we found our prize: a specimen of Krempf’s pine. Looking like a broad-leafed Podocarpus from only ten feet away, though on close examination it held its new “candles” like a pine, and smelled like a pine when crushed. We happily collected needles and herbarium sheets.
The next day we drove to Xuan Tho, a section of Đà Lạ t, to see a stand of native Taxus wallichiana, the Himalayan yew, and to collect cuttings for the Taxus collection at Smith College, a collection used extensively for anti-cancer research. It was the height of Vietnam’s coffee boom, and the whole area showed a recent conversion to plantations, as Viet coffee gained in stature among gourmets. At 1420 meters, we walked down a slope toward a small stream bed. Nepenthes smilesii, a vinelike pitcher plant, was growing among the grassy understory of this pine forest. Only two yews remained, one a substantial specimen, eighty feet high with a basal diameter of four to five feet. On our return to the institute, we stopped at the home of a local plant collector, a forester, in whose lathe house grew numerous orchids alongside a locally-collected specimen of Cephalotaxus mannii, a gymnosperm within the Cephalotaxaceae, from which he generously provided us cuttings.
After a hard night’s rain, the dawn broke clear, and we loaded our war-vintage Russian jeep and headed out of town, driving past schoolchildren trudging down the road in neat blue uniforms. We wove through a quilt of grassy pinelands and carefully tended, productive family farms. Nine kilometers from the institute, we halted beside a roadside grove of Keteleeria evelyniana that had recently suffered through a forest fire. Plants from the collection we made there currently grow with Dr. Jason Smith of Florida State University. Another species, Keteleeria roulettii, had been reported as endemic to the Đà Lạt area, based on the observation of longer needles. But from our observations of K. evelyniana, it was clear that fire had caused a series of new shoots to regenerate longer juvenile foliage, and this character was probably the basis of a false “new” species. It is no longer recognized.
We continued on the muddy red-orange road upward through a pine savannah, very similar to the longleaf pine forests of southern Georgia, into an unpopulated and relatively undisturbed piece of geography. About twenty-eight kilometers from the institute, we stopped at 1700 meters altitude in the area known as Lán Chanh. Putting our packs to our backs, we marched to the crest of a small hill. Looking down into the valley, we could see a drastic change in the vegetation: the piney grassland became a primeval evergreen forest, moist, dark, and lush. Rising above it all, a towering example of the pine we had come so far to see and collect, Pinus krempfii. Rather than having a spire-like habit, this forest giant had a broad crown, more like an oak than any pine I could remember seeing.
We eased downslope toward the sounds of birds trilling and a river’s flow, crossing a transition zone so narrow we felt as though we had stepped through a glass wall into a terrarium. Suddenly we trod upon a soft spongy humus soil dotted with ferns and seedlings of the evergreen trees around us. So many primitive angiosperms were present—Magnolia of the Magnoliaceae, Illicium of the Illiciaceae, Sacandra of the Chloranthaceae—it seemed a forest undisturbed since the Cretaceous era. Orchids were common, having fallen from the branches above, species of Dendrobium, Bulbophyllum and Epigeneium that would be precious to any orchid fancier. We made our way to the large pine we had seen from the hilltop, which proved a tree of mythic proportions: about 120 feet high with a trunk circumference of eighteen feet, the first branch at a height of seventy-five feet. Climbing the tree to harvest cones would have been unreasonably risky without climbing equipment, so we had to forage for what we could find on the ground.
Our party of five took to combing the forest floor, looking for fallen cones from prior years that might still harbor a seed or two, or for seedlings and saplings we might dig up. At one point I searched farther away from the party only to be cautioned by Dr. Tran to come back into the fold. “There are tigers,” he warned. We found 4 younger trees and about twenty seedlings to bring to our respective institutes. The leaves were so unlike any I had ever seen, curving blades 4 mm wide by 6 cm long, held in pairs. Cones that we found in the forest duff were easily recognized as pine. We also collected cuttings of Podocarpus neriifolius, along with some of the epiphytic orchids fallen from their perches above, and a smattering of ferns and seed.
Our Vietnamese colleagues seemed intent on getting out of the forest as quickly as possible, and counseled against crossing the valley to look for more trees. I recollected Dr. Xuan’s warning in Hanoi, and was relieved to think that we had avoided any peril beyond the usual rigors of the field. In any case, I already had collected a cache of rarities for our Smith College conservatory, and we had precious DNA samples for genetic work. We rose out of the ravine, over the grassy slopes and down to our waiting vehicle. We lunched at the side of the road, fine French-style baguettes, local fruit and imported soft cheese. Our success fueled our good mood and we sat on the side of the road, talking about our various plant specialties and favorite species. I glanced down at my feet and saw in the road’s gutter a weathered bullet casing, American made, a probable relict from the war that once tore both nations apart. It was my final collection of the day.
The few seedlings we brought out seemed to languish in the heat of our New England summer, and eventually died. Despite numerous hormone treatments, none of our cuttings rooted (though this is typical for pines). Other than the lonely plant at the Cong Ty Park in Đà Lạt, the only plant I could find in cultivation is held in the conservatory at Royal Botanic Garden Edinburgh. Groves of Krempf’s pine also are found within the boundaries of the Bidoup Nui Ba National Park, established in 2004, though their remoteness may make them susceptible to illegal timber poaching. Pinus krempfii remains aloof, distant and beckoning still. Given its great height, future collectors may need collection equipment like that used for Sequoiadendron: a bow and stringed arrow followed by ascension gear, with skilled arborists acquiring a supply of seed for ex-situ work.
Growing ex-situ specimens outside native ranges requires a combination of factors: the correct climate conditions (whether in a conservatory or outside), a long-term infrastructure of skilled horticulturists, and institutional will. The correct climate conditions would seem to be the biggest stumbling block for Krempf’s pine, as it grows in montane tropical or cloud-forest conditions without extremes of cold or heat. Its hardiness is not known. Some of the mildest areas of the California coast and upper altitudes in Puerto Rico may serve as potential US sites, though hurricanes would be a factor in Puerto Rico. But as was shown with Metasequoia, it can be a fool’s game to make hardiness assumptions based on a current restricted population range.
As elsewhere, the war of the trees continues in Vietnam, though thankfully the wars of the humans there have subsided. For all its rarity, Pinus krempfii is a magnificent holdout against angiosperm domination, one of the most amazing species I have ever seen in a long career collecting plants. In discussing local politics, Dr. Xuan had once told me, “In Vietnam, nothing is possible but everything is possible”; the latter part of that truism seems to apply to the flora as well.
The author dedicates this piece to the memory of Dr. Melvin Shemluck, who caught him when he fell from trees.
Over a 43-year career, Rob Nicholson worked for three New England botanic gardens, undertaking over thirty plant collecting expeditions for collections building, conservation, and medical and botanical research, and making 1,920 wild collections for the Arnold Arboretum.
Bibliography
Brodribb, T. and Field T. 2008. Evolutionary significance of a flat-leaved Pinus in Vietnamese rainforest. New Phytologist. 178 (1): 201–209.
Candolle, Augustin Pyramus de. 1820. “Géographie botanique,” in Cuvier, F. ed., Dictionnaire des sciences naturelles. Paris: Le Normant. Vol. 18: 384.
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