By the Tempuscene, bamboo and sunflowers together make up the vast majority of tree-like plants, each forming the foundation of a major forest communities. Most generally bamboo thrive where conditions are wet and sunflowers are more tolerant of drier environments, though there is overlap. With a few notable exceptions most extant bamboo is primitive, forming enormous clumps that reproduce most effectively via spreading runners. Serinan Sunflowers by 25 million years PE, however, have changed dramatically and in often remarkable ways.
Wherever rainfall is insufficient for the growth of bamboo thickets but more than is necessary for prairie grasses, a sunflower forest crops up. A far cry from the barren monoculture ecosystems of a very young Serina, the sunflower forest today is a unique, balanced ecosystem comprising many species and organisms and one that varies considerably across the world. All are defined, however, by the tall, broad-leaved flowering plants that form their canopies - gigantic, branching sunflowers that live for many years and build up their branching stalks with cellulose, eventually forming a woody trunk and reaching great heights. Sunflower trees are a polyphyletic grouping, descended from many distinct ancestors which have converged on a similar appearance in response to the same environmental condition; for example, tropical and temperate species are unrelated, as are most desert and rainforest species. Indeed at least four sunflower lineages independently developed a tree-like growth habit, surviving for a number of years without dying to the ground and building upon their old growth year after year, but superficially they are all very similar, with woody trunks that branch going upwards into many smaller growing shoots. The leaves are broad, flat, and generally nutritious to herbivores, either hairy, as in the ancestral sunflower, or smooth, depending on the species. All sunflower trees have shorter lifespans than most woody Earth trees, between ten and twenty years, but due to a rapid growth rate, this is fully sufficient to reach sizes of 60 feet tall or greater. Sunflower trees reproduce through seeds that follow often very bright and showy blossoms - sometimes still cheery and yellow and sometimes quite distinct from their ancestors - that are pollinated by beetles and honey ants or not too infrequently the wind, these trees having insignificant and colorless blossoms without noticeable petals.
Just like the modern sunflower, the seeds of sunflower trees are extremely nutritious and desirable to birds. In temperate climates, the survival of young birds in their first winter can be completely reliant on the success of the seed crop that year. If the trees don't produce large crops in the autumn, the young are unable to fatten up sufficiently to survive migration and starve. Flocks of millions and not infrequently billions of seed-eating songbirds gather when crops are heavy, gathering on the bristly branches so thickly that they hang limply under their combined weight. In the tropics, sunflower trees are equivalent to Earth's figs - there is almost always one fruiting somewhere, always providing a reliable food source to jungle animals no matter the time of year. Since sunflower trees grow rapidly, they are among the first plants to colonize cleared ground after a fire, but individual trees are extremely susceptible to flames and burn up rapidly, their sap highly flammable and their lightweight, corky wood extremely combustible. A lengthy wildfire can completely destroy vast tracts of sunflower forest, burning hot enough to completely break down the trees' trunks to ash and cinders and leaving little more than a field of charcoal in their wake, and is often fueled by the dried leaves, fallen flowers, and dead branches that tend to accumulate under the forest in the dry environments in which they thrive. In just a few months, however, a completely charred forest which seems hopelessly destroyed will return to a bright green garden as the trees return in the form of sucker shoots sent up by the tree's roots and seeds buried in the soil. Forests tend to burn down completely at least every other decade and regenerate, meaning few ever truly reach their potential natural lifespans or sizes, but incredible growth rates and maturity offset this. A sunflower tree can easily grow fifteen feet tall and then flower abundantly in its first year - a benefit of evolving from an annually-growing roadside wildflower - meaning that even the shortest season is usually enough to complete a generation. Wherever a sunflower tree does manage to grow to its full fifty or sixty foot height, however, it is truly a sight to behold. A single tree may arch over with ten thousand blossoms, attracting millions of pollinators in the brief two to three weeks before it loses its petals and becomes an unexceptional green tree once again for the remainder of the year. Aardgeese browse the nutritious green shoots and leaves extensively.
The understory of the sunflower forest is usually a patchwork of smaller shrubs, clover, short fern-like grasses that spread along the shady soil, and periodic clearings where wildflowers grow in dense carpets out from the leaf litter. Among the most successful forest shrubs are the long-lived, thorny derivatives of dandelions that grow several meters above the ground on raised woody stems. They thrive in the shade, but their flowers worship the sun. They periodically send up giant, antennae-like flower stalks through the canopy and into the open air as much as five meters above, where ants can reach them to pollinate and where the seeds can then be taken by the wind and dispersed into distant forest clearings. Though they sprout only where the ground is clear and the sun unobstructed, they do not die out when the trees return and close the canopy like many other pioneer species. Instead they just slow down a bit, growing over many decades in the shade, seeing many sunflower trees come and go in their time. When the forest goes up in flame they die to the ground and regrow quickly from their roots, being all but invincible to most natural phenomena the forest can throw at them.
Dandelion bushes are also highly successful desert plants, often forming dense stands on the dry borders between savannah and scrub, but it is the sunflowers which are are the dominant tree-like plant in Serina's deserts. Here, multiple genera have come to resemble not trees but cacti, having convergently evolved fleshy, barrel-shaped trunks to store water, reduced or fully absent leaves, and sharp protective thorns and hairs on their soft tissues to protect against evaporation and the hungering of herbivores. Desert sunflower trees are longer lived than forest species, and some may live for half a century or longer, for fire is infrequent in the true desert - there is rarely enough fuel. Like true cacti, these desert sunflowers produce beautiful and extravagant blossoms during the rainy season, blossoms which produce large quantities of nectar and attract both insects and pollinating birds. However, as the minimal resources of the desert do not allow for a massive overproduction of seeds to counteract the great number eaten by wildlife, these sunflowers have evolved a different strategy to spread their seeds. Instead of producing great quantities of large, bare seeds desirable to animals as a food source, they produce smaller numbers of smaller seeds with extremely hard shells encased in sweet, fleshy berries. Birds consume the fruits whole, rather than concentrating on the seeds, and pass the seeds intact in their droppings, dispersing them and helping the plant to reproduce