Tree of the Week: Live Oak (Quercus virginiana) update

Two weeks ago we studied our two live oaks (Quercus virginiana). These trees were not looking their best: they were mostly bare and the remaining leaves were brown. It was speculated that they might have suffered from the unusually cold winter weather because aren't live oaks always green? As it turns out, we simply caught them at a bad time, and the annual leafless period coincidentally followed the week of frigid temperatures. 

New leaves and catkins are already out! Both are yellow-green, very different from the glossy dark green leaves we see the rest of the year.

 

New leaves and catkins, photographed March 28, 2021

 

New leaves and catkins, photographed March 28, 2021

Live Oak (Quercus virginiana)

 

Do our live oaks (Quercus virginiana) typically look this bare in late winter? Across campus and throughout Shreveport, Live Oaks turned brown and dropped their leaves shortly after the mid-February winter storm weather. Since the unusually frigid weather caused obvious changes to other native species, we are taking a closer look at the live oak. 

We tend to think of live oaks as evergreen. You can find an old blog post, with many nice pictures, in which this species is described as evergreen. However, the literature describes live oaks as deciduous, dropping leaves in late winter or early spring. We're left with a quandary. Perhaps the timing is coincidental and the cold, icy, snowy weather had nothing to do with the simultaneous browning of the live oaks. 

But the USDA fact sheet calls our attention to a concern; according to the USDA, the minimum temperature for Quercus virginiana is 7ºF. Our recorded low temperature for February 16th was 2ºF. Let's see what happens!

Tree of the Week: Live Oak (Quercus virginiana)

The live oak (Quercus virginiana) is an iconic southern tree. Its historical native range is primarily restricted to the Gulf Coast of the Deep South, but it has long been planted in our local, inland landscapes, and with good reason. Other than its handsome appearance, much could be said in favor of its robust constitution. The live oak is a drought-tolerant, salt-tolerant, long-lived, and moderately fast-growing shade tree that makes for excellent hardwood lumber (think Old Ironsides, the USS Constitution).

The century-old grounds of Centenary College offers many fine examples of the live oak species. You can find long rows of live oaks along the eastern and western edges of the campus. In the arboretum collection, we have two examples. They were foundational plantings of the Morehead Memorial Concourse, completed in 1957. The planting of these two trees antedates both the construction of Hamilton Hall and the founding of the arboretum.

Our tree of the week is a live oak. It is pictured center. It's more than 60 years old. 

The live oak is an evergreen tree, and in this photo, it's surrounded by other evergreen species. We are lucky in northwest Louisiana to have so much green in December!

The live oak is known for having a short trunk with thick, heavy, low-hanging branches that spread out horizontally. Non-native Asian jasmine covers the roots of this specimen.

The bark on the trunk is thick, rough and dark.

The simple, narrow live oak leaves are dark green. Some leaves, like the one pictured above, have toothed edges. This leaf measures less than 4 inches in length.

Underneath, the leaves are a very light shade of green.

These leaves measure less than 3 inches. They are dark green with an elliptical shape. Leaf edges vary between wavy and toothed.

Light green underneath

Water oak leaves (left) are similar to live oak leaves (right). These leaves are approximately the same length, and they are all simple with slightly wavy edges. The live oak leaves are darker green and have a pointed tip.

If we flip the leaves over, the live oak leaf is clearly lighter underneath, almost white.

Also, the water oak has a few fuzzy spots along its midrib.

Unlike the water oak, the live oak is an evergreen tree. Here, on the young branches of the live oak, we see acorn caps mixed in with the evergreen leaves.

Empty live oak acorn caps and leaves

Ditto

Cups abound, while acorns are scarce.

Most caps were firmly attached to their twigs. These few caps were wiggled loosed.

Live oak acorn caps measure about a half inch in length.

Live oak acorn caps are cup-shaped, which is to say they are deep, rather than shallow.

For comparison, the water oak acorn caps are saucer-shaped, or shallow. Three water oak acorn caps are pictured on the left. Three live oak acorn caps are pictured on the right.

At this point in the season, it was difficult to find live oak acorns on the ground. These mini-mortar shells are approximately an inch long.

For more information about this species consult the following:
United States Department of Agriculture
University of Florida IFAS Extension
Louisiana Plant Identification and Interactive Virtual Tours (LSU AgCenter)
NC State University