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!

Tree of the Week: Bois D'arc (Maclura pomifera)

It's getting towards the end of July and northwest Louisiana is under a heat advisory. Its hot, hot, hot. What better time to talk about shade trees? The bois d'arc (Maclura pomifera) is largely known and recognized by its unusual fruit: a mostly inedible green, softball-sized syncarp. These drop to the ground in late summer and early fall. Although the fruit might not be edible, we can appreciate the great work these trees are doing to provide relief from the sun.

We have a solitary bois d'arc in the arboretum collection. In 2000, Ed Leuck collected bois d'arc fruit from East Kings Highway in Shreveport, quite close to Centenary's campus. Those seeds germinated in the campus greenhouse, and the most promising specimen was planted as a small tree in 2004. We presume it to be male, since it hasn't produced fruit. This species is dioecious, individual trees are either male or female, unlike many species of plants. The tree is doing so well, and the fruit of the species is so odd, that adding a female counterpart to the collection might be in order.

The Maclura pomifera in the arboretum collection is approximately 16 years old. It's a healthy tree, helping to shade the paths of the arboretum. All photos were taken at approximately 11 a.m., on a very hot, sunny July day.

Not much grows under this bois d'arc, probably because of the heavy shade and the slope of the hill. Unfortunately this creates an erosion problem, exposing tree roots. The orange root of the bois d'arc can be seen in the photo above.

The roots of the bois d'arc are characteristically orange.

Only a little light hits the ground under the bois d'arc. On the other side, the concrete sidewalk is brightly lit by the late morning sun.

Looking up, the branches of the bois d'arc jut out in every direction from the trunk, a much wilder display of branches when compared with last week's tree-of-the-week, Fagus grandifolia.

Branchlet of Maclura pomifera blocking the sun

The simple leaves of Maclura pomifera have an egg-like shape but are distinctly pointed at the tip.

When working near a bois d'arc tree, one must watch out for the thorns.

A young crossvine (Bignonia capreolata) climbs the trunk of Maclura pomifera.

You can find additional images of this tree here.

For more information about this species consult the following:
Louisiana Plant Identification and Interactive Virtual Tours
Texas Native Plants Database
United States Department of Agriculture

What's in Bloom?

It's the first day of spring. Trees are blooming. Vines are blooming. Wildflowers are blooming. Flowers are easy to find this time of year. Some flowers are large and hard to miss, attracting the eye with brilliant hues. Other flowers are subtle, small and white. And other flowers don't look like flowers at all; they look like 'weeds'. Below we have a small selection of the great variety of plants in bloom.

The red buckeye (Aesculus pavia) is still in bloom, with even more flowers this week. The red flowers contrast with the green foliage, forcing us to notice them.

The bees notice them, too

In contrast to the red buckeye, the silverbell (Halesia diptera) produces a small, inconspicuous flower. We used a clipboard for a backdrop to more easily see the flowers.

Looking up, the silverbell flowers are more obvious.

The crossvine (Bignonia capreolata) produces red-orange flowers, in the shape of a trumpet.

Even though they are brilliantly colored, crossvine flowers are easy to miss because the vine climbs up high. This vine has grown happily with a loblolly pine (Pinus taeda).

This is the first iris bloom of the season in the arboretum. This particular plant (Iris fulva) is a volunteer, growing in a drier spot than it should be, suggesting that the sprinklers have been doing a good job in this part of the arboretum.

Iris fulva detail

Additional Louisiana irises have opened up in the wetland.

Senecio glabellus is one of those 'weedy' looking wildflowers. It grows happily in wet areas. The flower smells like honey.

We are holding off on mowing the grass in the arboretum because of plants like the daisy fleabane (Erigeron sp.). They are truly wild, growing wherever they please. There are several healthy patches in the arboretum. And, like the Senecio, they have a pleasant smell. Enjoy them while you can!

Bignonia capreolata