The Nanboo Forest

Nanboo are enormous forest-forming grasses which evolved in Serina's tropics in the early Pangeacene, which can reach heights of up to one hundred and fifty feet. Their growth habit is bamboo-like and the trunks above ground originate from a large underground rhizome which spreads via underground runners, but the nature of the trunks is very different. Nanboo lack the ability to produce woody tissue and thus the entire above ground portion of the plant is actually composed of leaves which sprout directly from the root system; they are thus actually enormous herbs, and not proper trees. The trunk is formed by greatly enlarged petioles, or leaf stalks, which are hollow and tube-like. New leaf blades sprout up through the tube of older ones, which expand outward to accommodate them, only unfurling once they reach the top of the tube. Subsequently, the next leaf produced rises up through the hollow center of the previous leaf and so on until a trunk-like form is obtained, actually many tightly-packed layers of leaf stems growing up through one another. Each new leaf becomes longer and wider than those before it so that over time, the oldest leaves on the outer edges of the stem eventually can expand no further and split, drying and shedding onto the ground. The result, after the growth of many leaves, is a thick, fleshy trunk composed of dozens of condensed stems supporting a cluster of large strap-like leaves at its top. This growth habit is shared exactly with banana plants on Earth, from which the nanboo inherits half of its common name and closely resembles. The emergent leaves at the top of the nanboo's trunk, in addition to the hidden length in the center of the stem, can grow an additional thirty feet long and ten feet wide, making them unquestionably the largest single leaves of any plant.

Combining the herbaceous nature of banana plants with the large spreading root systems of the grass family, nanboo are highly vigorous and extraordinarily fast-growing plants when mature, some species able to add six feet or more of stem height per day when growing from a large root stock. Because their stems are soft, they can be produced extremely quickly, making nanboo forests especially resilient to natural disasters. Severe weather conditions, such as hurricanes, which would devastate communities of woody trees for years are only a nuisance to established nanboo forests, which can recover to heights of ten to twenty feet or more in only a few weeks' time when conditions improve by relying on energy stored in the gigantic underground root system alone. Though it may take them considerably longer to restore their previous heights, this is more than sufficient to dramatically out-compete any potential competitors starting from seed and to return the soil to shaded conditions. Nanboo are thus more or less immune to the natural process of succession once established and will hold their place in a forest ecosystem indefinitely unless long-term climactic conditions change substantially.

Nanboo seedlings can survive in a variety of light conditions, from full sun to deep shade, though grow most vigorously in open conditions. Seedlings generally cannot establish themselves well in ant forests because they are trimmed indefinitely and prevented from reaching the canopy, but established colonies with much greater rates of growth are a rare example of a plant which can overtake them. New stems rising from the soil and approaching an ant tree are chewed and attacked defensively, like any competitor, but whereas other plants would be stopped from growing if their tops were trimmed, this is not the case for nanboo. Just like how small grasses can continue to grow even when their tops are cut by grazers, but on a massive scale, nanboo grows from the bottom up in opposite to most plants and thus will continue attaining height even if its top is chewed off, reaching toward the canopy and eventually surpassing it. Once here, it is largely left alone by the insects, which don't target the trunks of other trees but only their new growth, and can spread its leaves over the tops of the other trees, shading them out. Nanboo forest readily becomes the dominant forest community in the tropics, where rainfall is reliable and abundant, allowing them to overtake almost all competitors. In dry conditions, however, nanboo is extremely unsuited, as its soft stems are totally unguarded against dehydration. The drier a climate becomes moving across Serina from the equator toward the interior desert, the nanboo present there become shorter and less vigorous, eventually reduced to a ground cover of short herbs less than a meter high and growing in the shade of woody trees where they are protected from drying winds. Nanboo is also limited by cold, its above ground stems being killed by temperatures below freezing and its sizes in seasonal environments therefore limited to as much as it can obtain in a single growing season as it dies back to its roots each winter.

Nanboo are remarkably vigorous plants which can out-compete almost all comers in ideal environmental conditions and dominate Serina's wettest equatorial environments almost exclusively. The largest tree-like forms, however, are notably limited in their distribution because without stable, ideal conditions, its vigor rapidly declines and it loses ground to slower-growing but more adaptable woody plants. Because of these constraints, nanboo is not usually a major forest-forming plant in temperate forests, nor in arid climates or regions where rainfall is seasonal, and thus ant trees and other sunflowers continue to thrive in abundance over most of Serina.

Even in drier environments, however, there are occasional circumstances that will allow for the formation of a nanboo-dominated woodland, if only temporarily. Most frequently, this comes about after an intense wildfire swipes through a community of woody plants, killing the majority and opening the forest floor up to a flood of sunlight. If the fire is followed within a few months' time by a period of rain, nanboo formerly growing as a short carpet of herbs on the previously shaded forest floor will respond to the change and grow rapidly to tree-like proportions many times their former height, briefly shading out competitors and bursting into flower and setting seed before the dry season returns and causes them to die back to the ground. They may get two or even three seasons as trees before the woody trees recover and begin to shade them out, relegating them back into the shadows. Some species of nanboo rely on this circumstance exclusively and will only flower after fire, when the rest of the forest is killed back, and which spend most of their lives otherwise, sometimes for decades, as low-growing under story plants.

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Nanboo trunks each flower only once, much like early bamboo. The flower bud, like the leaves, originates from the roots and grows upward on a rigid stem through the center of the trunk, eventually rising beyond it to heights in the tallest species of up to 175 feet, making them at least by measurement of their height the largest flowers ever to exist. The flower stem is very wide and more rigid than the leaves, causing the trunk to split as it pushes up through it so that by the time it reaches the top of the stem, the original trunk and therefore the stem's leaves have torn apart and dropped to the ground, leaving a single immensely tall blossom stalk standing freely in the forest, sometimes more than five feet wide at its base. Blooming is a grand affair. Distantly related to chokeweed, nanboo belongs to the same ancient group of grasses which evolved to produce colorful flowers pollinated by animals, and its flowers are very showy indeed. They are born on the stem in great panicles which may collectively contain ten thousand or more, each two to three inches wide and colored brightly yellow, pink, or even blue and which are pollinated mainly by tribbats and birds, with specific species often having preferred pollinators. Some are white, intended to attract nocturnal animals and thus opened only at night. The flowers contain deep nectaries accessible only to animals with long bills, like birds, or tongues, like tribbats, and are thus not very attractive to most insects except certain beetles with long extensible proboscis which can be dipped into the blossoms to feed. After pollination, the massive flower produces a glut of fig-like fruits favored by myriad creatures, which disperse their seeds in their droppings or on their bodies. Once the last fruit has ripened, the flower stalk withers and falls to the ground, but the colony which produced it survives and thus the plant as a whole is perennial.

above: a brightly-colored tribbat extends its jaws to reach the deep nectaries of a giant nanboo blossom.

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Though flowering is an extraordinary event in the nanboo, it is also a relatively rare one. Though in the tropics at least a few blooming and fruiting stalks can be found at any one time over any given area and are among the most important food sources to many jungle animals, they are far outnumbered by flowerless stems and indeed the vast majority of trunks will never produce a bloom stalk, and those which will are predetermined from the time they are produced by the root system. The more numerous non-flowering stems typically cease growth shortly after surpassing the canopy and thereafter cease to grow any more leaves, lasting for several years before dying off and serving only to produce energy for the colony via photosynthesis. Flowering only begins once a colony is many years old and most reproduction occurs through the spreading of the root system, which can over time result in a single colony covering several miles of land - effectively a superorganism, and surely among the largest ever to exist. There is a danger to such a lack of genetic diversity, however, in that periodically plagues may wipe out entire forests. By reproducing through sexual means periodically and producing offspring with a new gene combination, the nanboo assures its future security, as at least some of these outbred seedlings, produced in such numbers as they are, will likely be resistant to any pathogens which may wipe out their fore-bearers.