French Mulberry (Callicarpa americana)

 

Toward the end of spring, we noted that the French mulberry flowers are without pizzazz (read here). The flowers are small and hidden and they simply do not dazzle.

The fruits, however, are wonderfully bright. Their sharp coloration is much appreciated in the August landscape. Some fruits are ripening now, while other shrubs are on a different timer, ripening through the month of August and into September. 

 

This shrub near the southwest corner of Mickle is covered in ripe fruits, but other shrubs in the arboretum have yet to begin the process.

Fruits are edible straight from the shrub, but they do taste better when used to make jelly. Yum!

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 

Tadpoles (Anaxyrus sp.)

The campus is rather quiet over the summer, and the Frost Garden's fountain is also taking a break. During this hiatus, our recent high volume of rain has created an interesting artificial circumstance.

 

The fountain and its surroundings in the garden are clean and tidy.

Upon closer inspection, we can see an unexpected hidden pool. The rainwater is tinted slightly yellow due to leaves and algae, which appear green due to the fountain's interior blue paint. Wait a minute, what's that?

Something's swimming in there. A lot of somethings!

There are literally hundreds of Anaxyrus tadpoles here. A few were observed (not shown in this photo) that already had spindly legs developed. The arboretum curator also rescued several adult toads responsible for this invasion. They could hop in to spawn, but got stuck and couldn't get out.

Here we have a few of the larger specimens. Removing any tadpoles from the fountain is a mercy, because while it provides an excellent nursery, they will have to leave to survive. There's no way for the baby toads to get out!

 

The arboretum features a few locations where water tends to pool even when conditions are dry. The headwaters of the upper pond's stream are one such place, as a few gallons of shaded water are often present.

This location is directly below Randle's, by the cypress trees, and it offers a reasonable spot for a few buckets of tadpoles.

The water is cloudy after being disturbed by our bucket of amphibians. Thankfully the animals weren't shocked by the change in water quality. They were still alive an hour later, and even on the following day! We can't be sure if these are American Toad, Southern Toad, or Fowler's Toad, as all three are native to Louisiana. Given the reported ranges, it's most likely Fowler's Toad (Anaxyrus fowleri).

External links

Brad Glorioso's page on the American Toad 

Brad Glorioso's page on Fowler's Toad

2018 US Department of Defense Fact Sheet on Fowler's Toad 

Brad Glorioso's page on the Southern Toad 

Vine Removal

The appearance of Asian jasmine climbing red bricks is pleasant and romantic.

On the other hand, it's invasive, non-native, and unduly exerting its influence over the arboretum. Begone!

 

Here the heavy, awkward sheets of jasmine have been pulled off the wall and piled up at the base. They (five-to-ten interwoven vines per foot of wall!) still have to be sliced & diced to separate them from the root networks.

Now the architectural appeal of the brick retaining wall is able to be appreciated more effectively. The vines were nice, but this is also good. And don't worry; the jasmine will be back to making its vertical advance after a year or two of regrouping.

Montezuma Bald Cypress (Taxodium mucronatum)

The genus Taxodium has three living members. First and greatest is T. distichum, our famous bald cypress, which is found up and down the Mississippi embayment, the Gulf Coast, and the Atlantic seaboard from Delaware to Miami. Less well-known is T. ascendens, the pond cypress, which has a similar but much reduced range. Finally there is T. mucronatum, the Montezuma bald cypress, whose native range is mostly within Mexico and Central America, although a few of the Texas counties on the Rio Grande are counted as well.

Consequently, the Montezuma bald cypress isn't native to Louisiana or the southeastern United States. But having all three Taxodium species in the arboretum allows any visitor to see for themselves the dissimilarities that exist within this one genus.

There are two Montezuma bald cypresses in the arboretum collection. Way back in the '80s, Professor Leuck purchased their predecessors from Woodlanders Nursery (Aiken, SC), and he planted them in his yard on Albany Avenue in Shreveport. In 1994, Professor Leuck collected and rooted two cuttings from the Albany Avenue property, and in the fall of 1995, he planted the new trees on the periphery of the arboretum, near the lower level entrance to the Student Union Building.

The Montezuma bald cypresses are tucked in between the two staircases, flanking the doorway. Today, this is the entrance to the Post Office. Thirty years ago in 1995, it was the entrance to the campus bookstore. These trees have witnessed a great deal of change.

 

On the left side of the doorway, we see the southern-most tree. Its trunk is noticeably thicker.

 

On the right side of the doorway, we see the northern-most tree. Its trunk has a smaller diameter. Given that these trees are growing far north of their native zone, maybe its microclimate exposure to colder weather makes this the slower-growing specimen.

The staircase provides a neat vantage point, and it also allows us to see the leaves up close. Over the years, the lower limbs of the cypresses were removed so that pedestrians could easily move about without ducking all of those branches.

The soft, feather-like needles are arranged either in an alternate or spiralling pattern. The needles are mostly evergreen under good conditions, lasting until spring when they drop to make way for new growth.

Here we see approximately 40 pairs of needles on one branchlet. Unfortunately the number of needles varies quite a bit and isn't particularly diagnostic between species. The small blunted tips of each needle gave rise to the binomial species name; mucronatum refers to an abruptly angled point.

The southernmost tree has the thicker trunk, potentially because it has access to more sunlight. Its trunk has fewer lower limbs.

The trunk with the smaller diameter has more lower limbs. 

An additional photo, showing the relative heights of the two trees, would be useful here. Perhaps the thinner-trunked tree is taller. And we forgot something else! In the future we need to add photos of these trees' cypress knees... just kidding! They don't have any. This is typical of Taxodium mucronatum, and the absence of knees on a cypress should set off alarm bells that one isn't dealing with the typical bald cypress.

 

 Useful external links

US Forest Service page on T. mucronatum 

USDA Plant Database profile on T. mucronatum 

Post Oak (Quercus stellata)

 

Storm winds shook the trees of the arboretum last week, rustling branches and scattering loose twigs onto the ground. Although messy, this provides us with ample opportunity to study and compare a broad sample of leaves. Our big old mature trees tend to drop only their lower branches, leaving their fresh summer-time foliage out of reach. One such specimen is the aged post oak (Quercus stellata) standing near the Student Union Building. Its gnarly branches are way up high, but this week some of those upper story leaves were knocked out of the canopy.

From the ground, there were a lot of nice leaves to sort through. We see variations in size and shape, but the general shape description runs the same: roughly cross-shaped with five lobes. Although, does anyone else get the feeling that these leaves are reaching out for hugs?

This photo aptly captures one prominent quality of the leaf surface: shininess! With the leaves laying flat on the pavement, sunlight bounces off the leaf surface.

Standing the leaf up against the wet bricks takes away some of the shine.

Irregular leaves make tree identification difficult. But, if you already know that it's a post oak, you can appreciate the irregularity, and say, "Hey, that's an interesting shape! Cool."

An irregular, but still more-or-less recognizable, post oak leaf

Late Spring Flowers

Our long, rainy, pleasant spring officially concludes next week with the Summer solstice. In the photos below, we have two late-Spring flowers to compare. Some flowers are showy, with flashing color that catches the eye; others are small and nearly hidden. 

These bright yellow flowers are certainly of the former eye-catching variety. Golden St. Johns wort (Hypericum frondosum) has been part of the arboretum collection since 1990. It was initially planted near Mickle Hall. After about 20 years, surrounding trees and shrubs grew up around it, blocking too much of the sunlight, steadily reducing the size of the shrub. So a few years ago we took action to preserve the small remaining shrub. It's been transplanted to a more open area, along the gravel path that runs between the Fitness Center and the Student Union Building. 

  

Bees were so active on the St. John's wort that they were difficult to photograph! Slow down, ladies, you're too busy!

 

French mulberry (Callicarpa americana) also flowers in late spring. Clusters of tiny white flowers can be found on the numerous French mulberry shrubs spread out across the arboretum. 

These seemingly non-descript flowers introduce a contradiction when compared to their later product:  clusters of beautiful purple berries that brighten the sweltering August landscape.