I received this question from a former student:

I’m taking a tree ID class this fall, and I’m preparing for it by reviewing some of the Latin tree names we’ll be learning. I came across one, quercus rubra (red oak), that I have a question on. Shouldn’t it be quercus rubrus? (Or querca rubra – but if I remember correctly, usually the adjective ending changes instead of the noun in cases like that.)

Just wondered if you happen to know! Also, though I can accurately tell my plant professor what “table” is in Latin (whether he cares or not), I have found some of the vocab we learned in Lingua Latina to be very helpful for plants! 🙂

Here is my reply:

It’s good to hear from you. I hope you’re doing well!

This is a subject I have always wanted to dedicate time to. I am fascinated by trees, and of course, they are all scientifically named in Latin.   Unfortunately, life is not permitted me to go down this trail.   I kind of envy you.  🙂

So, quercus is a weird word.   Your professor is correct.  Quercus looks like a masculine second declension word.   But, it is actually one of those rare feminine fourth declension words.   This is why the adjective is also feminine.  Thus, quercus rubra.   By the way, you probably know this already, but the word Albuquerque is a combination of quercus and albus.   pretty cool, huh?