Monday, November 20, 2017

Quercity—Thoughts on Oaks

Coast live oaks, Quercus agrifolia, in the California Coast Range.

Free time has been scarce lately, so I’m offering a short post on oaks, inspired by “Querc-y Characters” at the Lady Bird Johnson Wildflower Center website.

I have a fondness for the Wildflower Center that surfaces at the least provocation, for I once talked plants with Lady Bird! It was 40 years ago, when I was botanist and sole employee of the Wyoming Natural Diversity Database. Jane Sullivan, wife of the governor, invited a small group of botanically-inclined ladies to gather for tea with Mrs. Johnson in Jackson Hole, at the base of the Grand Tetons. Conversation was awkward at first, but Lady Bird had done her homework, and as we introduced ourselves, she responded with what she had heard or read about our work. Soon we were happily discussing plants. Afternoon tea is not my idea of fun in the Tetons—I prefer hiking. But I really enjoyed my time with Lady Bird. She was so gracious and down-to-earth, a wonderful mix.

Now to the oaks …
Bur oak leaves, Dugout Gulch Botanical Area in the Black Hills.
In Wyoming, we have two oaks, both at the edge of their range here. Bur oak, Quercus macrocarpa, is a tree of the eastern and midwestern US that reaches its westernmost extent in northeastern Wyoming, mainly in the Black Hills. Gambel oak, Quercus gambelli, is common in Colorado and the southwestern US, but in Wyoming it grows only in the Sierra Madre, near Colorado. I was going to add “northernmost extent” but when I checked the NRCS PLANTS Database distribution map, I discovered that Gambel oak has been reported from South Dakota! However, there’s no county recorded, and the Forest Service FEIS treatment doesn't mention South Dakota. This would be a major disjunction, and news to me. But it’s an oak matter for another time.
Gambel oak; source.
In a way, we’re lucky we have just two oaks in Wyoming. I worked several winters in southeast Arizona, and struggled with the oak situation there. Apparently it’s even worse in Texas … or better, if you're not obligated to come up with identifications. Texas has more oak species than any other state in the US. Amy McCullough has put together an elegant straightforward guide to four of the common ones in Central Texas: Querc-y Characters, illustrated by Samantha N. Peters. Besides being a work of art, it shows clearly the characters and challenges in oak identification.
If you’re a hardcore oak fan, or looking for a botanical adventure, check out Quercus in the Flora of North America (FNA). There are 90 oak species in North America according to taxonomist Kevin Nixon, who prepared the FNA treatment. The exact number is debatable because oaks hybridize readily. “An astounding number of hybrid combinations have been reported in the literature, and many of these have been given species names, either before or after their hybrid status was known. … Hybridization in most cases results in solitary unusual trees or scattered clusters of intermediate individuals.” Oh dear!!

Even if you’re not up for a Querc-y Mega-Challenge, you might find Nixon’s introduction interesting—a revealing glimpse into the tortured world of oak taxonomists.
“A representative selection of mature sun leaves” is required for oak identification. Shade leaves won’t do. These are leaves of the coast live oak—sun above, shade below.


  1. What a beautiful post about Oaks! Living as I do in the middle of what used to be Oak Savanna/Prairie country, I'm a big fan of the Quercus species. I don't know how many species we have here in Wisconsin, but they're certainly plentiful (especially in the southern part of the state). Bur Oaks are so majestic! How wonderful that you not only met Lady Bird Johnson, but you had an interesting conversation with her. Great post!

  2. Thanks, Beth. You are lucky to have plenty of oaks. I miss oak diversity actually. Our bur oaks don't get very large -- definitely not big enough to call "majestic" and in some cases more like dense scrub oak! (e.g. when fire or logging opens up pine forest)

  3. I've always loved oak trees. And I have about 10 black and red oaks in my backyard and one shingle oak. Had a massive white oak when we first moved here but it was struck and killed by lightning. The two beeches in its shade have really taken off since them.

    1. Hi Lynn -- it is interesting how many of us love oaks! Several friends said that in response to the post also. You are lucky to have them close at hand.

  4. Lovely to have a bit of an autobiographical post :)
    Do you get galls on your oaks in the US?

    1. Thanks, Tim :) Yes, there are galls. They were fairly common where I lived in California as a kid, on coastal live oaks.