Fruit
Fruit, while botanically classified as the seed-bearing structure in flowering plants formed from the ovary after flowering, more colloquially refers to the fleshy seed-associated structures of a plant edible raw to humans, and that taste sweet or sour.
Since climate change has warmed the Earth considerably, all fruit-producing plant species that remain can grow in tropical or sub-tropical climates.
#Human relations
Humans have eaten fruit since before we evolved into humans, and continue to enjoy fruit in the Fifth World. They eat fruits raw, squeeze them into juices, mash them into compotes, or dry them for later consumption. They may cook fruits with meat and vegetables, or combine dried fruit and meat to eat while traveling, in dishes like pemmican. Some people even preserve fruits in jams, by pickling them, or by fermenting the juice into wine.
#Fruit People
A community specializing in relationship with fruit may hunt and gather, picking and eating fruits as they find them. Many tropical and sub-tropical fruit trees and bushes grow throughout the Fifth World, although most of the ones outside of the tropics would have gotten there through purposeful cultivation by humans. Perhaps this fruit-loving community of hunter-gatherers wandered into an abandoned territory once controlled by gardeners. Or perhaps they snatch fruits from unwary neighbors' orchards. More likely, fruit trees spread naturally into their territory from gardens the old-fashioned way: birds ate the fruits from gardens, flew overhead, and dropped the seeds in handy packets of fertilizer. A community reaping the fruits (literally) of the birds' labor might feel quite grateful to the birds for helping plants travel across the world. Though they may not personally garden (probably feeling they don't have to), they may admire the birds for spreading fruits far from their original plantings.
Alternatively, they may practice horticulture, living in settled villages at least part of the year and making sure to plant exactly the fruit they like. They almost certainly plant fruit trees in guilds with other plants, such as in banana circles. They may practice Inga alley cropping (where the Inga trees themselves produce fruits for consumption, as well as fixing nitrogen in the soil and providing shade to choke out weeds) or swidden cultivation. A more settled, complex community of this sort would likely preserve their fruits for later -- by drying them, by pickling them, by mashing them into jams, or by fermenting the juice into wine. These latter methods would require the capability to store things in closable containers. They may store them in stoppered dried gourds (implying that they also grow gourds, possibly as part of the Three Sisters guild), or they may practice ceramics or even glass-blowing. Preserved fruit products in such containers would give them a valuable good to trade with other communities -- particularly wine, which remains popular everywhere in the Fifth World.
Most communities live somewhere on that continuum, scattering the seeds of fruits they enjoy more or less intentionally to plant more. Fruits provide a source of rare (and much-loved) sugar that, unlike honey, doesn't require putting oneself at risk of bee stings to obtain. They also provide fiber and vitamins, making them both delicious and healthy. And one can easily sow their seeds to ensure more fruits in the future. So this sort of community -- which enjoys fruit and only sometimes helps cultivate it -- likely sees fruit as a great gift. They probably celebrate the many different kinds of fruits they eat in festivals held throughout the year (depending on each fruit's season).
A community specializing in relationship with oranges in particular may not remember that oranges help boost immunity because they contain a lot of vitamin C, nor what their ancestors meant when they referred to "vitamins." But the connection between oranges and maintaining health, particularly when sick with the common cold, remains. They may become known for their nutritional healing knowledge. Perhaps having long ago begun interplanting orange trees with guava (which also contain lots of vitamin C) to naturally prevent citrus greening, their orchards may include many fruits with immune-boosting properties. They might preserve and trade this fruit with other communities, or perhaps they host festivals on part of their territory, in which case the oranges help ward off the colds that naturally arise from people gathering in unusually large groups.
Preserved fruits can particularly come in handy for long sea voyages, and at the poles where plants go dormant for the long dark season. A community specializing in relationship with fruits may live on the coast and travel extensively by boat, making dried and otherwise preserved fruit essential for avoiding scurvy. Or they may live at the poles, and desire something other than meat and mushrooms during the winter. (Or perhaps both!) In both cases, the community must harvest fruits when ripe, eating some but preserving others. A community located on the coast, particularly on a popular sea-trading route, may not practice sea-trading themselves, but plant fruit trees expressly to provide traders with fresh fruit on their voyage (and entice them to stop and trade their exotic goods).