Tree of the Week: River Birch (Betula nigra)

It's still winter in Louisiana. Most of the trees are leafless. It's a good time to appreciate the diversity of tree bark in the arboretum. Our tree of the week is identified primarily by its bark. You might see the river birch (Betula nigra) around town, planted as an ornamental tree in lawns and commercial landscapes. In the long hot Louisiana summers the leaves of the river birch provide much needed shade for our buildings and sidewalks. Now that it's winter, the leaves are gone, revealing the interesting form of the tree and its characteristic peeling-flaky bark.

There is one river birch in the arboretum collection. In 1985, two river birches were purchased from Clyde Gorum's Nursery in Shreveport. They were planted on the south side of the long wooden bridge. Ten years later, in 1995, one of the two trees was buried two feet under an embankment that was constructed around the lower pond. The tree survived and is thriving today. It's companion was removed in 2007, due to extensive insect damage.  

The river birch, over 30 years old, is growing in the corner of the embankment overlooking the arboretum's drainage basin. The leaves of two tree palmettos (Sabal palmetto) are partially obscuring the divided trunk of the river birch.

This is one tree with multiple stems.

The tree was planted before the embankment was constructed. In 1995, approximately two feet of dirt was piled up around the base of the tree to construct this wooden retaining wall. The tree didn't have a problem with the extra dirt.

Here we are standing in the drainage basin flanked by tree palmettos. This picture shows the river birch's tripartite trunk.

The river birch and wooden railing have grown very close over the years, perhaps too close, with the river birch complaining of needing 'space' and the railing complaining about being leaned on too much.

This is the characteristic river birch bark. It's shaggy, peeling, flaking, and rough. The top layer of bark is grayish-white, and it peels back to show a reddish-orange layer. This section has been worn off by the long, heavy palm leaves of the tree palmettos.

This is another look at the shaggy, peeling, rough bark with hues of maroon and orange. The LSU AgCenter describes it as 'salmon colored'. Check out their pictures in the link below.

For more information about the river birch consult the following links:
Louisiana Plant Identification and Interactive Virtual Tours (LSU AgCenter)
Virginia Tech Dendrology
U.S. Department of Agriculture, Forest Service 
United States Department of Agriculture

Tree of the Week: Water Locust (Gleditsia aquatica)

The winter months are a great time to appreciate our water locust (Gleditsia aquatica). This is a water-loving tree that typically grows in wet, soggy areas. Unfortunately, what's good for the tree is also good for breeding mosquitoes. Right now, we have moments of perfect weather without the irksome bloodsuckers. And despite being leafless, the water locust has plenty of winter-time interest: this tree produces spikes that recall a medieval torture chamber!

We have one water locust in the arboretum collection. It was collected locally, on the west shore of Cross Lake, at the home of Centenary professor Dana Kress. The specimen was collected in spring 1995, and planted the following November. It was planted in what was historically the lower pond of the arboretum. Although that permanent body of water was dismantled more than a decade ago, this area remains the wettest part of the arboretum. Several water-loving plants thrive in this area: bald cypress, Louisiana irises, palmettos, and river birch.

Addendum: The genus Gleditsia got its common name 'locust' from a similarity to a Middle Eastern tree, the carob, whose fruits resemble the locust insect.

The water locust can be found near the long white wooden bridge. It is growing beneath the embankment in an area that was historically called the lower pond. Today, water no longer accumulates in the area, but due to its status as a drainage basin, it remains the wettest section of the arboretum. The water locust is pictured center, on the other side of the wooden guardrail. On the far right of the photograph, we have two palmetto trees and a grouping of river birch.

Standing in the 'lower pond', we get another view. The water locust is again pictured center. Sabal palmetto is to the left of the locust. Louisiana irises cover the ground.

The palmetto casts an interesting shadow on the trunk of the water locust.

Having a look at the ground around the water locust, it appears as if the locust has knees like the bald cypress (Taxodium distichum). This is a trick. The bald cypress is simply an opportunist and sends its knees up wherever is pleases, including in the space allotted to the water locust. These knees could belong to either of the two bald cypresses.

Getting a little closer to the water locust, we see that this tree is well armed.

The red-tinged spikes are impressive.

Presumably these spikes protect the tree in some way. Perhaps the spikes dissuade wildlife from devouring the (tasty?) fruits or leaves.

Bald cypress leaves have collected on the lower spikes.

The spikes provide spider-habitat. This picture also captures the undulating surface of the trunk. It isn't round, but rather rippling, similar to the muscular trunk of the ironwood (Carpinus caroliniana).

The bark is gray and bumpy.

You can find additional information about this species from the following sources:
Stephen F. Austin University State University
United States Department of Agriculture 
University of Florida IFAS Extension
Virginia Tech Dendrology