Women as allegory for the life force of plants - or just a plant biology lesson?

[bi3mw]

...  Does anyone know when and how plants’ reproduction was described in the 15thCentury and earlier? I’d love to know! ...

I remember Boethius. In "Consolatio Philosophiae" he describes in the third book (Liber Tertius) :

lat:        Iam uero quanta est naturae diligentia, ut cuncta semine multiplicato propagentur.

engl:    Again, how great indeed is nature's care, that all things should be propagated by the
            multiplication of seeds.

The views of Boethius certainly reached into the late Middle Ages. The description of nature influenced the way of thinking at that time ( and later scribes ). I don't  know an old, technical description of plants’ reproduction.