European Middle Ages
From about 200 to 850 intellectual and technological advances were minimal. In the absence of centralized authority there was widespread instability as feudalism gradually took hold. Recorded plant knowledge across Christendom was confined to the poorly copied works of Dioscorides and the even more degenerate Herbarium Apuleius. The first rather clumsy Latin translation of Dioscorides’s Materia Medica was probably by Martialis around 250 but a literal translation was made aroud 500 and used by Italian, Frankish and Salernitan doctors: this was the textual foundation for most of the medieval manuscripts of Dioscorides.
From about 850 with feudal states providing social cohesion there was a marked improvement in material conditions and enquiry.
Christianity & the two empires
Emperor Constantine I (c. 272-337, ruling from 306 CE) allowed freedom of worship to Christians and was pronounced the the official state religion by Theodosius in 380 CE (r. 379-395). Christianity continued although the western Roman empire collapsed when Rome was sacked by the Visigoths in 410 CE. After the decline of the former classical world the human intellect became occupied with religious rather than scientific matters. Through the 4th to 6th centuries Roman administration gradually divided the empire into eastern and western halves, the capital being transferred from Rome to Byzantium (which later became Constantinople, then Istanbul).
In the early seventh century, Greek became the official language of the eastern Byzantine Empire where the learning of Classical antiquity was respected and ancient skills were retained as demonstrated by the mathematical and engineering skills needed to construct the magnificent domed Hagia Sophia building that still stands today in Istanbul, completed in four and a half years (532–537 CE). However, after the 6th century Byzantine scholars made few new scientific advances.
While Europe was in the intellectual doldrums with ancient texts lost or forgotten there was a revival in the Syrian capital city of Edessa which was located on the Silk Road at an intersection of both east-west and north-south trade routes. This was both direct Roman control and alongside the rival Persian Empire resulting in the rise of a wealthy and educated merchant class deeply interested in Greek science and followers of Nestor, a theologian from Antioch, whose views were regarded as heretical by the established Church.
China had meanwhile passed through a descriptive and encyclopaedic phase with similar nomenclature to that of the west but without a Dark Age, eventually uniting with Western botany in the nineteenth century. But all this was still essentially ‘applied’ botany.