Maypop (Passiflora incarnata)

 

A delightful seasonal treasure thrives at the base of an eastern red cedar trunk. See our previous post on this plant here.

Purple flowers bloom on this bush-shaped vine. The flowers seem to be best during the morning hours.

These flowers, some wilting and some blooming, are awesome to behold. Note the sneaky anole, pictured center. That's a reptilian "photobomb."

What amazing colors and shapes are present here, part of a totally wild and unselected plant. And, looking closer, you can see a developing fruit.

And the 'great reward,' a green fruit shaped somewhat like a hen's egg, is hidden among the leaves.

The flesh of these fruits tastes tropical, sweet, and very light.

Visit the maypop before it gets gobbled up by the Gulf Fritillaries! We haven't seen any fritillaries in the arboretum yet, but they were spotted elsewhere in the Parish, presumably laying their eggs. We expect the spiky black-and-orange catepillars to eat these leaves.

Laurel Cherry (Prunus caroliniana)

 

Prunus is a famous, useful, and diverse genus. When you're "kind of a big deal," you typically have more problems come your way.

Here we see sap leaking from regularly-spaced wounds on the trunk of this laurel cherry (Prunus caroliniana).

This is likely the early stages of a condition arborists call "gummosis." The French botanist Auguste Trécul (1818-1896) was first to note, circa 1860, that a condition resulting in a superabundance of sap around a pathological zone could result from a variety of maladies. That name refers to the liquefaction of a tree's inner wood material and its leaking from wounds in the tree. This gummosis, or Gummibildung and even Gummifluss, as the Germans call it, can help protect a tree by isolating infected wood between hardened, protective plates. As it is really more of a physiological response than a disease itself, there is no singular cause of gummosis; it can result from insect damage, climatological stress, or infection by bacteria and fungi. 

Here we can see an old wound and the gummosis above it.

Back in June, this tree was placed on the docket for removal, primarily because of its significant lean. You can read that post here. The gummosis is not the reason for removal, but it did speed up the process. Enquiring minds want to know―what does the inner bark look like given the external gumminess? Is there a bug infestation or is it rotting? So the Faustian spirit urges, "Cut it down! Let's find out!"

 We are fortunate to have a volunteer ready to take its place. We'll stake that one and try to avoid the leaning tower of laurel.

In order to avoid destroying the smaller laurel cherry at the base, we first took out all the branches. Cutting most of the way through allowed us to extract the plant material slowly.

Here the tree has been separated into trunk and branches for easier disposal.

Here we can see the damage at the base of the trunk, which probably gave rise to the gummosis. Our working theory is that this damage was isolated and more-or-less healed by the tree. Later attacks by bugs or sapsuckers, in a vertical line from this damage, resulted in the tree leaking sap due to its proximity to the old wound.

The trunk ought to be round—and a crescent-shaped portion is clearly missing. What we don't see here is a lot of rotten material, a bug infestation, fungal infection, or other bad signs. The tree was, at least right now, apparently healthy despite the manifestation of gummosis. Nevertheless, we stand by the decision we made to cut it down, in large part due to the uncorrectable lean. In an unexpected turn, this newly cut lumber produced an aroma which corresponded precisely to a cherry soda.

All cleaned up and immediately replaced by the volunteer, who will reap great rewards in sunlight, nutrients, and water.

A Bacterial Gummosis of Cherries (1911) by F. L. Griffin

Gummosis of Prunus & Citrus (1911) by Ormond Butler

Solomon's Seal (Polygonatum biflorum)

The arrestingly-named Solomon's seal (Polygonatum biflorum) is a handsome herbaceous plant. Its obscure common name is well-paired with its genus name, Polygonatum (which comes from the Greek gonatos)  and means "many-kneed." Do plants have knees? What does all this mean? We won't dwell on the unanswerable. There are a few dozen species in the genus, but most find their home in East Asia, far from Caddo Parish, Louisiana. 

As far as names go, we have a problem; our current signage turns out to be inaccurate. The arboretum catalogue shows two collection dates for hairy Solomon's seal (Polygonatum pubescens), both dating from the '90s. In 1991, Professor Ed Leuck collected a few plants from within Shreveport's city limits, on Line Avenue. A healthy patch still grows under the origianl red buckeye plants. In 1996 Jack Price of Blanchard donated six pots. Those plants have thrived on the southwest side of the long wooden bridge that runs from the Student Union Building to Mickle Hall. This patch continues to grow out into the lawn. Plants were collected from the grassy area and then transplanted to other areas of the arboretum, resulting in two additional patches of Solomon's seal. So, there are four total patches of Solomon's seal, and the original two patches are marked with green signs that read 'Solomon seal (Polygonatum pubescens)'. 

This is a relatively new patch of Solomon's seal. In 2023, we relocated a couple of plants to this spot, alongside a young black cherry (Prunus serotina). The black cherry has since grown tall, shading the Solomon seal.

The fruits were noticed several weeks ago. 

Leaves alternate and have noticeable ridges or veins.

As the bell-like flowers of Solomon's seal descended daintily and prettily from the stalks, so now do the berries.

These fruits greatly resemble blueberries, although they are much more firm. Be careful! NC State Extension claims, "The berries, if eaten, are poisonous."

Dark blue round fruits measure less than ½ inch across.

 

Squeezing the large fruit opens the bright green interior, revealing numerous seeds. Seven seeds came from one fruit. Another yielded four seeds.

 

Looking at the current classification information for Polygonatum in the United States shows P. pubescens and P. biflorum are the two major species east of the Mississippi. However, a distribution map clearly shows that P. pubescens is not found in the Deep South; its homelands begin in the mountainous, cooler climates of Kentucky and Tennessee. Since the distribution map for P. biflorum makes much more sense in covering the entire eastern half of the USA, we needed to take a closer look at the plants currently growing in the arboretum.  

Descriptions for both species state the fruits are similar. Descriptions differ for flowers, leaf size and shape, and the presence of hairs. Since flowers aren't available in late summer, all four patches of Solomon's seal were studied for leaf size and shape and the presence of hairs. 

This egg-shaped leaf suggests P. biflorum.

These narrower, lanceolate-shaped leaves suggest P. pubescens. 

These leaves are from two different patches. Do we have two different species or different light-conditions? The top leaf was found in full-shade. The bottom leaf was found in partial shade.

 

 

Within the arboretum's collection, leaf size and shape suggest that we have two different species of Solomon's seal. However, the common names dwell on the presence of leaf hairs, and although the leaves varied in size and shape, no hairs were seen on any stems or leaves. All surfaces felt and looked smooth. 

This is the underside of the leaf. We see spots, but nothing fuzzy. 

The underside is smooth. Leaves and stems from all four patches were examined, and nothing resembling hairs was detected. 

Based on species distribution and the total absence of hairs, we shall change the arboretum catalogue to note that we have Polygonatum biflorum, rather than Polygonatum pubescens. And, in the spring, we must study the flowers to see if they can give us any other clue as to the correct species label.

 

 

For more information about this species, please consult the following online sources:

USDA Plant Database Info for Smooth Solomon's Seal

USDA Plant Database Info for Hairy Solomon's Seal

Flora of North America Species comparison for these two plants 

Plants of Louisiana

NC State Extension 

Black and Yellow Garden Spider (Argiope aurantia)

Boo! Autumn is a season for creepy-crawlies, spiders, and bugs. This is a female Argiope aurantia, which is Latin for 'golden silver-face.' This name makes a lot of sense, given that the cephalothorax (meaning head-body) is silver while the abdomen is gold and black. We know it's not a male because males of the species are much smaller, brown, and just plain ugly.

"Oh... what tangled webs we weave...." As members of the Araneidae family, these spides are "orb-weavers" and produce the classic spider-web.

This specimen was photographed on September 28, 2024, next to the long white wooden bridge in the arboretum.

 

For comparison, this photo is from insectidentification.org (image credit: Arch Baker).

Volunteers in the Arboretum

The overgrown area near the Student Union Building, previously referred to as 'the volunteer recruitment zone' or 'the Arboretum's unintended creche', is slowly being cultivated: we have removed Groundsel shrubs (Baccharis halimifolia) and Chinese privet (Ligustrum sinense). This week, we cleared around the sycamore (Platanus occidentalis), making it possible to read the sign and walk around the trunk.

The arboretum has only one sycamore on display, so we want to raise this tree's profile. Visitors ought to be able to read the sign and examine the trunk without too much difficulty. Right now, it looks a bit too hazardous; you might come away with some dewberry-scratches on your shins. 

There are numerous vines, little shrubs, and trees growing around the base of the trunk. Unfortunately they must be removed for the health and visibility of the sycamore.

The base of the trunk is now revealed. Several small trees were removed; elms (Ulmus sp.), oaks (Quercus sp.), and one black cherry (Prunus serotina) were snipped. We do not want any other trees to grow up next to the sycamore trunk, so it was an easy decision to remove these volunteers.

We used a lawn mower to cut the grass, making this space more inviting to foot traffic.

Several pieces of crossvine (Bignonia capreolata) had to be pulled from the trunk.

Dewberry (Rubus trivialis) was cleared away from the base of the trunk. This species comprised the bulk of the plant material surrounding the tree.

Dewberry vines have painful prickles. It's best to wear long pants when walking near a dewberry patch, but as the prickles snag on clothes, you still need to watch your step even if dressed defensively.

A small yaupon holly (Ilex vomitoria) was growing near the trunk, but not next to it. Yaupons do very well in the soil of the arboretum and they are common volunteers. This little shrub was allowed to stay for now and might very well be added to the catalogue.

Luckily, there were not any passionflower vines surrounding the sycamore. The abundance of Gulf fritillary butterflies tells us that we ought to refrain from pulling any passionflower―we want the caterpillars to have plenty to eat!

Cleanup Operations

Today, more than four months since it fell, we decided to complete the water locust (Gleditsia aquatica) clean-up operation. Most of the mess was cleared away during the month of May. Over the summer, a very large section of the trunk remained wedged inside the yaupon holly on which the water locust had collapsed.

 

A section of the water locust trunk is pictured on the far right of the photograph. It had been resting in the yaupon holly shrub for several months.

 

As this tree trunk was suspended off the ground, we are "stumped" as to its current rotted condition. There are numerous mushrooms growing on it. Why would a rot-resistant tree have rotted so quickly?

 

A chainsaw was required to reduce the trunk to movable pieces.

All cleaned up! The water locust is gone, which is sad, but the good news is that we have a young water locust to plant this winter.

Arboretum Cleanup: Catalpa (Catalpa bignonioides)

Maintaining trees in an urban landscape often requires pruning. Removing lower branches from trees allows for more foot traffic in proximity to the trees, and it also increases visibility, which is a safety concern. Some trees require more pruning than others. Today we'll take a look at one of our catalpas, which is in rude health. See previous posts on the history of this tree here and here.

 

The catalpa (Catalpa bignonioides) is pictured center. What a gorgeous tree. It is only eleven years old! Take a look at the trunk: there aren't any branches near the ground.

Even though the lower branches have been removed from the trunk, branches further up the trunk droop low to the ground.

The leaves and seed pods are only a couple of feet above the grass.

 We pruned this tree and its partner (not photographed), which lies across the drainage canal. With the lowest drooping branches removed, we see more of the landscape, and, more light is now available to the little trees and shrubs recently planted. The catalpa will hopefully invest its energy in its upper branches rather than the ones nearest the ground.