Bears, Burls, and Butter-butts

Top Photo: Mimi bear (right) and Gus bear.

After grazing on some winter grass, Mimi bear seemed to be headed for the culvert pipe attraction in her enclosure to slip inside for a nap. Gus bear was already engaged. With a sidelong glance at the slumbering male bear, Mimi slinked off to greener pastures.

Gus in slumber.
Mimi sends a sideways glance towards a relaxing Gus.
She moves on.

Recently, Ranger Brooke found a small piece of pine branch with a growth attached. She asked me what I thought it was. I reasoned it a gall. It was about 3” lengthwise, about the same size and shape as a blackberry knot gall (a blackberry bush’s reaction to tiny wasps laying eggs in its stems – see here – More Galls). But this object was very hard. Galls can typically be cut open with a pen knife. That didn’t work here.

Is this a gall?

I suggested we take the gall, or whatever it was, to the Exhibits Shop and see if we could have it cut down the middle on a band saw. If it was a gall it would have insect larvae inside.

Exhibits prototyper, KJ, gleefully offered to cut open the object. Inside, it was all wood. It was a burl.

Solid wood.
Beside the straight lines caused by saw, you can see circular grain growth contrary to the straight grain of the original branch.

According to Merriam-Webster online dictionary a burl is: a hard woody often flattened hemispherical outgrowth on a tree.

Another online dictionary defines a burl as: A rounded knotty growth on a tree, giving an attractive figure when polished and used especially for handcrafted objects and veneers.

In the UK you would refer to the growth as a bur or burr.

Burls are a tree’s reaction to an injury, virus or fungal infection, or insect infestation. The burl itself is not diseased nor does it contain diseased or contagious material. It contains bud material that hasn’t grown into branches or foliage but instead has grown into itself. It’s all wood inside, gnarly, twisted wood.

Burl at base of loblolly pine.

Burls can grow on branches, main trunks, or underground on the tree’s roots. The ones pictured here are all small burls, the largest about 8” across, but they can grow quite large, 20 feet or more in width and height.

Because of their intricate, twisted grain, they’re valued by craftspeople for woodworking as veneers, insets, instruments and implements.

Should you remove a burl from a living tree? Probably not. The tree is in no way harmed by the presence of a burl. However, if you cut out a burl you’re removing a living portion of the tree, exposing it to outside damage that otherwise would not occur.

Yellow-rumped warblers, a.k.a., myrtle warblers, a.k.a., butter-butts, have been ravaging the wax myrtle fruit all around campus. When the weather gets cold and insects become scarce the largely insectivorous warblers turn their attention toward wax myrtle fruit. If you stand still near one of these fruit laden shrubs you can watch the birds gorge themselves with the waxy fruit.

Two butter-butts attack wax myrtle fruit.
Reaching for the fruit.
Gulping it down.
There are seven warblers in this picture.
Acrobatic birds.
The fruit has a large hard seed inside a thin waxy coating.
Yellow-rumped warbler and wax myrtle.

If the cold, inclement weather persists, the birds make quick work of the fruit and move on in search of more. If you spot a feeding frenzy of these little parulid, fruit eating birds, appreciate it while you can. Once the fruit is gone, so are they.

Butter-butts help propagate wax myrtle shrubs. The waxy coating on the fruit prevents water from entering the seed. In order to germinate, the wax coating must be removed. By swallowing the fruit whole the bird’s digestive system does the work of extracting the wax, and out comes a seed ready to grow into a wax myrtle shrub, or tree. Well, almost ready. The seeds need to be cold stratified for about 90 days before they’ll sprout, but most of the work is done.

The End

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