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 

Spice Bush (Lindera benzoin)

Spice bush (Lindera benzoin) fruits are ripening in northwest Louisiana. The youngest spice bush in the arboretum collection has a surprising number of fruits.

 

In 2022, this spice bush volunteered among a grouping of fringe trees (Chionanthus virginicus). This photo was taken the following summer in 2023. At that time, this spice "bush" had one primary stem, suggesting that it might develop a tree habit.

 

Today, the spice bush looks decidedly more like a 'bush' than a small tree. In this photo, we see several distinct stems.

 

Our young spice bush is tagged. Not every entry in the arboretum catalogue has a sign―that would be too much clutter in the landscape. There are already two spice bush shrubs with signs in the arboretum.

 

Numerous fruits are hiding among the leaves.

Sitting *under* the shrub, it's much easier to see the fruits.

Fruits appear in clusters along the branch.

The bright red fruits are ⅜ inches long. According to North Carolina State Extension, the fruits are edible.

The large, green drooping leaves come to a point and the leaf-base is asymmetrical. Both leaf and fruit have a spicy fragrance.

Toothache Tree (Zanthoxylum clava-herculis) and Giant Swallowtail (Papilio cresphontes)

Over the past several years, the number of individual toothache trees in the arboretum has steadily increased. The mature tree at the southwest corner of Mickle Hall continues to produce an abundance of fruit, and little volunteers continue to pop up each year. We have allowed the young trees to continue growing, even in locations that are unsuitable in the long-term. For instance, despite there being no future in the aboretum for a volunteer growing next to the trunk of a large mature tree, their leaves can provide food for a very interesting caterpillar. 

Giant swallowtail (Papilio cresphontes) caterpillars have recently been spotted nibbling away on the leaves of a 4-year-old toothache tree (Zanthoxylum clava-herculis). Two caterpillars are captured in this photo. Do you see them?

Here we have another caterpillar, stuck to the spiny, slender trunk of the toothache tree.

They are funny looking creatures. You may even find their heterogenous and mottled appearance disgusting. They are camouflaged to resemble bird droppings! What wonderful diversity occurs in the natural world. And these critters are certainly thorough in their work of stripping the toothache tree of its foliage.

Rather than allowing the horde of caterpillars to defoliate a single tree, we remove a few individuals and place them on the volunteer toothache trees. As noted above, those trees that haven't been added to the catalogue because, based on their current location, they do not have a future in the arboretum.

We certainly want to make sure the caterpillars are well-fed--they turn into such lovely butterflies! Can you think of a better candidate for the "ugly duckling" of butterflies?

Passionflower in the Arboretum

Every year, Hummingbird Central puts out a map where users can report their first sightings of migratory hummingbirds. Let's play a similar game. Have you seen any Gulf fritillaries (Agraulis vanillae) yet? At the arboretum, we're still waiting on them. This year, the arboretum has two species of passionflower for the caterpillars to enjoy. 

Yellow passionflower (Passiflora lutea) can be found throughout the arboretum. It isn't cultivated in any particular spot and volunteers freely. Sometimes we have to pull it off other plants, and sometimes we allow it to climb and twine. This time of year, its quirky little flowers are on display. In this photo, the passionflower vine is attached to a yaupon holly (Ilex vomitoria).

 Also, this summer, we have something extra special. Maypop!

 

Last year we planted Maypop (Passiflora incarnata), specifically during the spring of 2024. In this post from the autumn of 2023, we made clear our intent to do just that. It grew for a short time, but the Gulf fritillary caterpillars soon devoured all of the leaves, so the vine was not given the opportunity to climb or flower. Surprisingly, the plant wasn't killed by this premature defoliation; it started growing again this spring. And it is thriving! There are plenty of leaves for the caterpillars this year. The vine is attempting to climb an old eastern red cedar trunk.

In late July, we are seeing the peculiar "spaceship" flowers, and still no sign of the Gulf fritillary caterpillars. Perhaps these vines will even produce fruit this year. If you've never had maypop fruit, you've missed out on something special! Yum!

Paw Paw (Asimina triloba)

Approaching the end of July, things are still looking green in the arboretum. Thus far, we have had an unexpectedly wet summer. We're around 8 inches in excess of our expected year-to-date precipitation (approximately 40 actual versus 32 expected) and we've had around 7 inches of rain since June 1st. That's enough to keep the frogs happy! New recruits in the arboretum are particularly thankful, one such specimen is pictured below:

This is a young paw paw (Asimina triloba). The young tree comes to us from the banks of the Missouri River in Nebraska, where it was collected by Mark Anderson. Mr. Anderson successfully germinated numerous seeds for a project on his Texas property and was kind enough to donate five plants to the arboretum. This past winter, we planted three paw paw saplings in the arboretum. One died, and one of the two survivors is shown in the photo. Since it's so easy for the weeds to overrun such a small individual, the regular application of elbow-grease (regular weed-pulling) is necessary, especially with all of the aforementioned summer rain. And after the weeds are removed, a layer of mulch must be added to the ground around the stem to prevent the dirt from drying out too fast.

Persimmon (Diospyros virginiana)

In October 2023, we identified and collected eight persimmon seeds from the Caney Lake district of Kisatchie National Forest in Webster Parish. The seeds were immediately planted in one big pot, and during the spring of 2024, they germinated. Seven seedlings grew vigorously in the same pot for approximately a year. 

This past spring, five of the saplings were planted in the arboretum, and two were set aside and repotted as a backup plan. Now that it's June, four out of the five saplings planted in the arboretum are alive, and one in particular looks great. The overall high germination rate and low mortality of these specimens shows how vigorously our native trees must fight for survival in wild conditions. Pampered and given every opportunity by helping human hands, they succeed easily.

This persimmon sapling grows in full sun toward the top of the grassy slope east of Rotary Hall. It is a year old. The trunk is very slender and wobbles under the weight of the big green leaves. Possums are eagerly awaiting the maturity of this tree, although it will be quite a few marsupial generations before any of them get a taste. Perhaps there's an old possum proverb: "The best time for an arboretum curator to plant a persimmon tree was ten generations ago."