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.

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."

Tulip Poplar (Liriodendron tulipifera)

Our little tulip poplar (Liriodendron tulipifera) is growing up nicely. In 2022, this individual volunteered on the north edge of the arboretum, down slope from mature tulip poplars. The following year it was extracted and relocated to a more suitable spot. 

 

In April 2023, the sapling was photographed against a black umbrella when it was less than 8 inches tall. Given that this species can grow to become one of the largest trees (over 100 feet) in Eastern North America, we have on record some modest beginnings.

                                     

Today, it looks healthy and appears to be living up to the expectation of being a 'fast-grower'. Pictured here in June 2025, we see that our tree has grown significantly. Based on photos from last December, it may have nearly doubled in height. The trunk exhibits a slight lean due to the  shade cast by a nearby swamp dogwood (Cornus foemina), but our tree has successfully outgrown that competition. Additional staking would be a prudent intervention to correct the current lean while the tree is still supple. In another decade it will be big enough to support numerous bees and moths with its leaves and nectar.

 

To see a post on the gorgeous fall colors offered by this specimen, click here. 

Summer Concerns; Irrigation in the Arboretum

Centenary College, "Where the sleepy, silver bayou, / Gleams among the pines...." The Alma Mater says that the campus once had a bayou. What happened to it? There are still a few big pine trees, but much has changed over the past hundred years. 

The growth of modern cities with their necessary infrastructure of concrete streets & sewerage has greatly altered local hydrology. Whereas in the past rains might saturate a richly developed soil, rainwater is now swiftly funneled across impermeable barriers of roof-and-road into storm sewers and drainage canals. For our purposes here this means that despite getting on average 50+ inches of rain per year, summer conditions can easily cause drought. Since we need to keep our wide array of arboretum species alive for academic purposes and keep the non-native grass alive for aesthetics, this means we need to supplement our natural precipitation with artificial irrigation, mostly in the form of sprinklers.

An in-ground network of pipes supplies well water to most of the arboretum, and much of that system can be programmed to run automatically. Some lines of irrigation must be manually turned on, and water hoses must be hauled and stretched to reach a few small patches.

The sprinkler system is an absolute necessity for maintaining the health of the arboretum. The fact that it can provide an amusing diversion is a nice side-benefit.

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.

Kentucky Coffee-Tree (Gymnocladus dioica)

In our contemporary situation of free and easy global trade, yearly consumption of coffee beans amounts to almost 25 billion pounds. You can get a cup almost anywhere, anytime. But since Coffea arabica can only be grown in a relatively few environments, war or trade embargoes can easily cut off coffee supplies to most places on earth. Due to this problem and the recognized benefits of the drink, coffee substitutes have often been sought and utilized. Today we'll showcase the arboretum's Kentucky coffee-tree (Gymnocladus dioica). 

 

It isn't native to Louisiana. The map below shows that the plant is really a Midwestern fellow, with its distribution dipping down into the southeast. 

This map shows the current distribution according to the USDA-NRCS. The Kentucky coffee-tree (Gymnocladus dioica) does not typically grow in Louisiana. Since it can be found in central Arkansas, this species certainly deserves representation in the Centenary arboretum.

There are two Kentucky coffee-trees growing in the arboretum. There is a big one, and right next to its trunk, there is a little one, which is clearly waiting for one of the surrounding trees to die so that it might have a chance to grow. These two trees do not have an official entry in the arboretum catalogue. They are mentioned elsewhere, in regards to other plants, but their specific planting history is missing. In an entry for spiderwort, the Kentucky coffee-tree is mentioned: "Another large clump [of spiderwort] with the seedling Gymnocladus dioica, below iris bed in west floodplain, planted 1999." A Kentucky coffee-tree seedling was growing in a pot with spiderwort, and they were planted together in the west floodplain in 1999. So, the Kentucky coffee-tree is at minimum 25 years old. According to the Iowa University Agriculture and Natural Resources Extension, the tree should be sexually mature and fruit-bearing once aged 20-30 years. Interestingly, this tree came to our attention this week because we found an unusual seed pod in the leaf litter.

This seedpod was found in the west floodplain under the Kentucky coffee-tree. Since the species is dioecious, that means our tree is female, but where is the male? How was it fertilized? The pod was cracked open and one seed was removed. It was in poor condition, so it was discarded.

Two more fruits were found. One is significantly larger.

The larger pod has one seed.

It's a large seed, mearsuing approximately one inch across.

The seed is round and dark brown.

As with the Yapuon holly (Ilex vomitoria), the Native American Indians of the Southeastern Woodlands are reputed to have consumed a tea made from the seeds of Gymnocladus dioica. The paucity of consumer goods in colonial times, being a major issues for homesteaders and travelers, there has been interest in this tree's seed since at least the late 18th century. Some people employed the Kentucky Coffee-Tree as a coffee-substitute up to and possibly during the American Civil War, when a Union blockade cut off the Confederate States of America from international trade. It was greatly inferior to the alternatives, such as chicory and scorched barley, as an uncaffeinated coffee substitute. Experiments performed by John P. Spaeth and John W. Thieret in the earlier 2000s showed that although potable, this drink was generally squalid. While true coffee addicts would consider such a product little better than a criminal act, a hot herbal beverage is better than nothing on cold days and long nights. Let's now check out the specimen itself.

The Kentucky coffee-tree is pictured center. It grows in a heavily shaded floodplain. All lower branches have been removed, so it will easily be missed as "just another tree" unless one is looking for it.

The wish-bone shape of this tree is no doubt a response to growing in heavily-shaded conditions. This tree is clearly adaptable.

It was planted near a Pinus taeda, an on-site native. From its first planting in the arboretum, the Kentucky coffee-tree has had to compete for sunlight, leaning away from the looming pine tree. Alas, it's good to have friends, even if you have to share your place in the sun. These trees have known each other for a long time.

The photos below were taken during the winter months. They allow us a less-cluttered view of the landscape.

 Clumps of spiderwort (Tradescantia ohiensis) grow at the base of the Kentucky coffee-tree trunk. Spiderwort was planted at the same time as the coffee-tree.

Kentucky coffee-tree has gorgeous papery bark.

 

The tree has an irregular growth pattern, as noted above. Hopefully this will not lead to cracking and breaking in the future.

Additional resources:

USDA Plant Profile on Kentucky Coffee-Tree

Lady Bird Johnson Wildflower Center

North Caroline Gardner Extension