This week, the birch.
There's not much to say about the birch in Latin literature, and that's largely because Latin literature does not say much about the birch.
The Latin for birch is betulla, and it only appears four times in the Roman Trees Database. All four appearances are from Pliny the Elder's Natural History, and only two of them, in consecutive sections, actually focus on the birch itself. This is unusual for a tree that is so widespread, and so recognisable.
So what do the Latin sources we have actually say about the birch tree?
It will not surprise regular readers that our source is Pliny the Elder, in his Natural History (16.75):
The birch... rejoices in cold places. [It] is a Gallic tree, of an amazing white colour and slenderness, a cause of fear, supplying the magistrates' rods. It is also easily bent to make hoops and likewise the ribs of small baskets, and the Gauls extract from it bitumen by boiling.
Pliny repeats that birch is used in baskets later in the Natural History, and adds elsewhere that it has good torsive strength.
And that is everything that we know about the betulla in Latin literature.
Unlike the ebony, which is valued for its colour, and the colour of which continues into the timber, the birch's 'amazing white colour' is reserved only for the tree's exterior. The timber itself, while pale, is not much different from that of the oak, which was readily available to Romans, and is far more widely spoken of. Additionally, the habitat of the birch, in the colder parts of northern Europe and extending into Scandinavia, even Lapland, may have made the birch an uninviting tree to import into Italy in large quantities, since it has little enticements below its bark.
Ultimately, and unfortunately for the birch, its status in Roman usage and thought is minimal (at least from the literary evidence we have). Depictions of it in magistrates' rods is widespread, although these depictions do not identify the species type, which is only accessible through the knowledge handed down by literary sources. The tree's attraction to Pliny is not for its timber in any grand construction, it is solely for baskets, barrels, and bitumen (if you're a Gaul), but is instead for its bark. For Pliny, the birch's beauty is only skin-deep.