Mexican Plum (Prunus mexicana)

We've added another Mexican plum (Prunus mexicana) to the arboretum catalogue. This species is a fan favorite, producing delectable and highly-colored fruits that make a complete mess during their season. Squirrels eat them; bugs eat them; we eat them. Raccoons and possums eat them after hours when nobody is looking. The mature trees produce so much fruit that it simply lays about on the ground. This time of year, if you look under any of those trees, you will find seedlings. The individual pictured below is one such seedling.

Last April, this young tree was collected from under the mature Mexican plum growing on the steep slope near Mickle Hall (see here). It survived transplanting and the long hot summer months thanks to an onerous watering regime. Today, it is almost a foot tall.

Since the fresh green leaves developed in full sun, we don't need to worry about shocking it with too much sunlight when we plant it.

We planted it in full sun near the top of a gradual slope on the north side of the Cline Hall dormitory. This is an open, grassy area, and this time of year we allow the wildflowers to grow tall. The stakes with pink tape are necessary for calling attention to our small tree—we don't want it to be stepped on, stomped flat, or mowed over.

Red Buckeye (Aesculus pavia)

On October 25, 2023, first-year students collected and planted seeds from red buckeyes in the arboretum. Approximately a month later, seedlings emerged from the dirt. Now, 16 months later, we see the first flowers! That's fast development.

Professor Rachel Johnson brought two groups of students to the arboretum for tours. The first group was from an 8 a.m. class. Students picked up 5 seeds and planted them in this spot, marked by the metal tag.

At minimum, three of the five seeds germinated. One plant remains, and it is short and wide, and it has one red panicle. 

This is full sun. Online literature says that red buckeyes can grow in full sun or shade, so this is one of our experimental spots for full sun conditions. The majority of our other buckeyes grow in part or full shade.

Students from Professor Johnson's noon class also planted 5 seeds. They were slower to germinate by just a week or two. Several seedlings emerged, and died back, and started again.

Today, we see two little plants. One is significantly larger than the other and it has one red panicle.

The arboretum has a steadily growing collection of red buckeyes. We are really hoping to draw in the ruby-throated hummingbirds with these clusters of pretty red flowers.

You can read more about the germination project on an earlier post, found here.

 

Winged Elm (Ulmus alata)

Today we added a young winged elm (Ulmus alata) to the arboretum collection. This species grows abundantly in Caddo Parish—it is very 'weedy'. There are three mature winged elms in the arboretum: one is an on-site native; one was intentionally collected from Walter B. Jacobs Nature Park in Caddo Parish; and one is a volunteer. Our new recruit was planted in full sun near Mickle Hall, and it is expected to flourish with very little maintenance.

This specimen was collected in Caddo Parish, just north of Shreveport. Discovered in 2023, after it had germinated in a pot of soil meant for another plant, it now enters the Centenary campus as a 2-year-old, measuring 18 inches tall.

Our little tree has already leafed-out. We see serrate leaf margins.

And looking closer, we see a slight ridge along the stem. This young tree is developing its corky 'wings', which help us identify this tree as a 'winged' elm. Sweet gum trees (Liquidambar styraciflua) also have this characteristic.

 

 

US Forest Service Ulmus alata Fact Sheet 

Bois D'arc (Maclura pomifera)

Three bois d'arc trees were planted on campus today. All are about a year old, and the tallest is approximately a foot high. You can read about the earlier stage of this project here, where we describe the collection and germination process.

We have three pots of bois d'arc (Maclura pomifera). Each pot has one main sapling, and there are several smaller saplings in each pot that will need to be trimmed back routinely until their roots die. We had such a high germination rate that we are now having to cut back seedlings that we do not have space for.

Our tallest sapling measures a foot high.

We already see new leaves on these young trees. You can also see a couple of thorns along the stem. 

We planted all three trees on the slope between the Student Union Building and Rotary Hall. They were sited along the southern side of the drainage channel. There is typically a small amount of water in this channel, year-round, so we are confident that the bois d'arc trees will find this to be one of the likeliest locations in the arboretum for their future success. Naturally, they will require frequent supplemental watering during their first summer, as they are not yet established.

A cottonwood (Populus deltoides) has thrived nearby. These trees ought to be great friends and get along splendidly, but there is surprisingly very little reference on the internet to them growing together. This must be due to the restricted natural range of the bois d'arc, which historically prevented it from colonizing all those areas suited to it. Self-described "desert rat" Gary Nored mentions on his blog that creekbeds in west Texas, along the US-Mexico border, are habitats for cottonwood and bois d'arc. Locally, we see mature bois d'arc and cottonwood growing together along the Clyde Fant Parkway. So, our bois d'arc saplings ought to do just fine.

In this photo, we are looking down the same slope, into the arboretum. A cottonwood is pictured at the far right edge of the frame. Our saplings are already planted, but they do not stand out in the landscape because of their small size. However, they are carefully marked with protective posts, and they will most likely grow quickly, making themselves more conspicuous.

 

Shortleaf Pine (Pinus echinata)

 

There is one shortleaf pine (Pinus echinata) in the arboretum collection. It is approximately 30 years old. In October 1997, two trees were purchased from Coyote Creek Nursery in southeast Louisiana. The following month, they were planted near the Student Union Building. Today, one tree remains.

The shortleaf pine is pictured center. It grows next to the sidewalk that runs between the Student Union Building and Cline Hall Dormitory.

The thin, flat plates on the trunk have a reddish tint.

And here we see the work of the yellow-bellied sap sucker (Sphyrapicus varius). There is a fairly straight, diagonal line of holes drilled across the trunk. At least the holes aren't actively weeping.

All of the limbs on the west side of the trunk have detached and falled off, presumably because they were heavily shaded by the nearby water oak (Quercus  nigra). The remaining lower limbs hang toward the open sidewalk, in full sun. 

Luckily this tree still has lower branches so that we can examine fresh spring-time twigs. Here we see reproductive activity. Shortleaf pines are monoecious, which means they have both male and female parts on the same tree. In this photo, we see a cluster of the pollen-producing catkins, and they are not open yet.

This twig was snipped without the aid of a ladder.

Shortleaf can be identified by the "short" needles that typically come in duos.

These needles measure less than 3 inches. By comparison, our loblolly (Pinus taeda) needles measure 7 inches long, and loblolly pines have three needles per bundle. 

Needles were removed so we could examine the catkins. According to Dr. Becky Barlow at Auburn University, catkins form in the spring while cones develop a few months later, higher in the tree. Catkins are a yearly product, while cones take two years to develop. A healthy, mature tree will therefore have staggered cohorts of pollen and cones.

At the current time, the catkins measure less than half an inch long. They will grow larger before releasing pollen.

USDA NRCS page on Shortleaf Pine

USDA Forest Service Southern Research documentation 

NC State University Gardener Page on Shortleaf Pine

The Shortleaf Pine Initiative

Turk's Cap (Malvaviscus arboreus)

Today we're adding a new perennial wildflower, Turk's cap (Malvaviscus arboreus), to the arboretum collection.

 

We ordered two small pots of Turk's cap from Almost Eden. It's a nursery in Merryville, located in southwest Louisiana on the border with Texas. This company has been in business for decades and grows many native plants that are suitable for our climate. 

Our plants arrived in perfect condition, in a long cardboard box, securely wrapped and taped. This box was built to accomodate up to four plants. We only needed two.

One leaf fell off during transit.

The other leaves help us confirm that this is Turk's cap. Although, when ordering plants, you shouldn't always expect to see leaves. Some plants will arrive as bare sticks, and that's okay, too.

But, it's nice to see the dentate leaves!

The nursery has provided a legible and informative tag. How helpful! Note: 'Big Momma' is spelled 'Momma', not 'Mama'. Dr. Greg Grant, a horticulturist in Smith county Texas, brought us this and other cultivars of Turk's Cap.

With the purchase of these two plants, we are hoping to add something extra pretty to the arboretum collection, so it sure would be nice if our two plants live up to their potential: "The deep scarlet red, 1-1/2" long, Turk's turban-like flowers are held upright and are produced in abundance from late spring or early summer until the first hard frost or freeze...."

Our two plants arrived taller than expected. The tallest measures two feet, and the other is 1 foot and 10 inches.

The 3.5" pots were packed with healthy roots that were ready for the earth.

The two plants were planted together near the southwest corner of Mickle Hall, behind one of our black, metal arboretum signs, and under a winged elm (Ulmus alata). The new plantings are inconspicuous in the winter landscape. Hopefully we will have bright red flowers and butterflies to appreciate while trudging up the hill this summer.

Native American Seed Co. classifies this as a good species for hummingbirds.

Dr. Greg Grant, the breeder who created Big Momma, blogs about his love for Turk's cap.

Almost Eden's page for this plant.

The USDA plant page for wax mallow. 

Lady Bird Johnson Wildflower Center page for Malvaviscus arboreus.

Slope Maintenance and Bridge Replacement

 

Another exhausting session of work on the disturbed slope, with temperatures in the 35 to 45 degree range. The clay is thankfully drying out, which makes it easier to manipulate.

Things are looking better, but it will probably be a year or two before nature heals. Since the ground has been so thoroughly disturbed, we ought to have a multitude of volunteers germinate in this spot. It will be interesting to see what comes up.

Going further down the slope, we see that the new bridge is complete! Wahoo! In the arboretum catalogue, this is referred to as 'the long white wooden bridge that runs from Mickle to the Student Union Building'. It's not white anymore.

 

Ought we paint the bridge white? Another color? Or is the bare look of treated lumber pleasing?

The large pile of materials is gone; craftsmen have used it up.

Here we can see the under-structure of the new bridge, along with some new pylons made of concrete block and treated lumber.

The new bridge also makes use of the old pylons.