Cypress Rust or Cypress Galls?

As students are currently flooding back onto campus and things are once again shifting into active term, your arboretum curator has taken the opportunity to remove branches and limbs from walking spaces. Living limbs, dead ones, branches covered in leaves, bare ones, and even the soft needles of cypress trees are being pruned away from the "head spaces" across the arboretum. While performing this seasonal maintenance near the Student Union Building, we noticed some rust-like growths in the pruned branches. Having struggled against cedar-apple rust (Gymnosporangium juniperii) for more than a decade, we are well-accustomed to unsightly rusts. But the simultaneous presence of white and purple growths on nearby branchlets made us do a double-take. 

 

What is going on with these cypress leaves? The unexpected amount of color variation gave us pause and attracted our attention.

 

These aren't rust at all! They're galls! Galls are growths created by tiny flies called cypress gall midges (Taxodiomyia sp.). These little critters are obligate parasites of the cypress, and the adult flies are terribly small. If you carefully dissected the large green-yellow gall on the right of the above photo, you could find tiny larvae crawling around in there, exerting chemical/enzymatic control over the tree. How odd!

Here we can see the life-cycle progress of gall-formation. They begin as white, budding, geometric-like structures seen on the left, which ripen into a frosty purple, pictured center. The galls then continue to mutate into more bulbous rusty lumps, like the one pictured on the right. These eventually fall from the tree and overwinter on the ground, finally releasing new midges during the following summer.

Beginning stage of gall development

Further development

Toward the end of gall development

 

See our previous post on this baldcypress from September 2019, which ends with a mention of this issue! Much water has passed under the bridge of life since then, but some things, including the Cecidomyiidae family of gall midges, never change.

 

 

External Link

NC State Extension Fact Sheet on Cypress Gall Midge 

Tree of the Week: Bald Cypress (Taxodium distichum)

 

For several months now, a lone stake has protruded from the ground near the sidewalk that leads to the Student Union Building. What's the point of that? Was it left there by mistake....for three months?

The stake marks an emerging cypress knee. This past spring, when the grasses, wildflowers and weeds were allowed to grow more than usual, the cypress knee was noticed and spared from the lawn mower blades.

This week the stake became a post: a label was affixed to the metal pole to explain its presence. Since we're in Louisiana, it's fair to assume that most folks will be able to recognize the brown woody formation as a cypress knee. But, where's the tree?

 

Our best guess is the nearest bald cypress (Taxodium distichum). It's growing on the opposite side of the sidewalk, partially concealed by a needle palm, Louisiana palmettos and an ever-expanding stand of Hercules'-club (Aralia spinosa). This bald cypress is more than 25 years old. In November 1995, Professor Jeff Trahan collected the specimen from C. Bickham Dickson Park in Shreveport. It was planted in the arboretum at the same time.

Immature Cypress Fruits

Pond Cypress (Taxodium ascendens)
growing near the Fitness Center
thin, needle-like leaves & immature, globose fruits
pictured July 12, 2020

Bald Cypress (Taxodium distichum)
growing next to the Fitness Center ramp
feathery leaves & immature, globose fruits
pictured July 12, 2020

Peculiarities of a Bald Cypress (Taxodium distichum)

Sometimes you look up and notice a really beautiful tree. Today we'll look at a series of pictures focusing on the trunk of this fine tree, followed by some other features of note.

This bald cypress (Taxodium distichum) grows on the north side of the arboretum, at the head of a drainage canal which empties catchment from a large section of campus. You can find more information about its history on a previous blog post, found here.

The tree partially shades the small parking lot near the Student Union Building and bandshell. Its elegant, drooping branches are beautiful, but they also require routine pruning to allow easy passage along the nearby sidewalk.

The trunk is more or less straight, although the tree itself is inclined.

Competition with an older, on-site native water oak has resulted in asymmetrical branching―the southeast face of the tree is nearly bare of branches. Most of the branches grow on the north and west sides of the trunk.

Despite the competition, the tree, about twenty-five years old, is in rude health.

With handsome bark and handsome root structure, few trees can top the bald cypress for looks.

The famous cypress "knees" can potentially be a problem. So far, this tree hasn't damaged anything we know about.

Conversely, its knees have taken hits from lawnmower blades over the years.

This time of year you'll find cypress fruits, green and sticky, growing in singles and clusters. These balls will separate into multiple scales, each of which is a seed. Apparently ducks enjoy them.

Looking closely at the feathery twigs, we noticed a strange growth. Can you spot the yellow formation?

Would you believe that the tiny white shapes in this photo (as well as the lumpy-looking mass in the previous photo) are fly galls? Yes, midge flies create these and use them to reproduce. How'd that evolve?

Tree of the Week: Bald Cypress (Taxodium distichum)

We are nearing the winter solstice. Most of the deciduous trees in northwest Louisiana have dropped their leaves. Those few deciduous trees retaining their leaves stand-out in the otherwise grey-green landscape. Our tree of the week is one such specimen. We have a bald cypress (Taxodium distichum) in the arboretum that is showing off its red-orange leaves this week, and making a mess of the long white wooden bridge. All photos below are of a single specimen, purchased from Gorum's Nursery in 1985.

The bald cypress is tall and orange. It's planted in a low spot, surrounded by vegetation. In this photo, an old yaupon holly bush obscures the lower portion of the bald cypress.

From another angle, yellow-green fall foliage of the arrow wood viburnum obscures the trunk of the bald cypress.

The long white wooden bridge (pictured left) runs on the south-side of the bald cypress.

The bald cypress has dropped a lot of leaves!

On the bridge, the red-orange bald cypress leaves are mixed in with water oak leaves.

Standing on the bridge, we can get a clear look at the handsome, gently tapering trunk of the bald cypress.

The base of the trunk is buttressed with pronounced ridges.

Cypress knees protrude from the ground, seemingly at random, in the vicinity of the tree. Sometimes they appear solo.

Sometimes we find a collection of knees.

Sometimes the knees are extra knobby. Can we treat them as clouds and imagine if they resemble something?

Looking up, we see straight limbs jutting out from a straight trunk with an orange backdrop.

Zooming in we see an orange mat of color.

Cypress leaves are little needles attached to a twig. This twig measures more than 2.5 inches long, and it holds approximately 50 leaves.

Twig length varies. This twig measures more than 4 inches long.

Needle length varies, too.

Tree of the Week: Bald Cypress (Taxodium distichum)

It has been an unusually rainy week here in Caddo parish, with still more rain in the forecast. The high temperatures have hovered around 90 degrees instead of 100. Hot and humid but not much sun. So, let's talk about a particularly water-loving shade tree, the bald cypress (Taxodium distichum).

There are five individual bald cypresses in the arboretum collection. The pictures below are all of the same tree, purchased from Home Depot, and planted in October 1993, at the top of the arboretum drainage. The pictures were taken on a partly cloudy day, shortly before 1PM. 

The light green foliage of this bald cypress (Taxodium distichum) blends in with the larger, on-site native water oaks (Quercus nigra). If you look closely, you will notice the pyramidal form of Taxodium distichum. 

This is a view of the top of the drainage system for the arboretum. Looking beyond the trunk of Taxodium distichum, we see the bandshell. When we get a heavy rain, water rushes down the slope and collects at this location, and then runs through the arboretum and out at the Fitness Center.

Standing under the tree, looking out, we can see that this Taxodium distichum shades much of the concrete drive.

Looking up, we can see the sun directly above. The foliage of Taxodium distichum isn't as dense as some of the trees we have looked at this summer, such as Fagus grandifolia.

Needle-bearing twigs elegantly hang from drooping branches.

The light-green foliage of Taxodium distichum has a 'feathery' appearance.

The individual needles are quite small, but they are densely stacked on a single twig, maintaining a relatively flat appearance.

There aren't a lot of cones on this particular tree, and right now, they are green.

Taxodium distichum has characteristically reddish-brown 'shreddy' bark.

Be careful not to trip around cypresses. There are several small clusters of knees, blending in with the grass.The purpose of the knees has not been conclusively determined by scientists.

This knee might be mistaken for a rock.

For more information about this species consult the following:
Texas Parks and Wildlife
Louisiana Plant Identification and Interactive Virtual Tours (LSU Ag Center) 
USDA Forest Service 

Taxodium distichum