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: Sycamore (Platanus occidentalis)

In northwest Louisiana, sycamore fruits are ripe this time of year. Numerous fruits hang from the upper twigs of the arboretum's only sycamore tree. The fruits are way up top, out of reach. Luckily, for the purpose of documentation, a single sycamore ball was found on the ground, among the several scattered branchlets.

 

The arboretum's sycamore is located near the Student Union Building. You can read about its history on an old blog post, found here.

 

This specimen has a very noticeable lean in its trunk. The sycamore has grown in response to the competition for sunrays: it's leaning away from two southern red oaks (Quercus falcata), one of which is a very large, on-site native.

The bark at the base of the trunk is dark brown and very rough.

 

Looking up, we see the characteristic light-colored bark, a few crinkled brown leaves, and the globose fruiting structures.

 

The sycamore ball, not quite as ignominious as the sweetgum ball, is an aggregate of tiny fruits, tightly bound together in a globose shape. Only one sycamore ball could be found in the leaf-litter for inspection.

When the fruits are ripe, sycamore balls are light brown, round, and large, measuring more than 1½ inches across. They are known to create a litter problem.

With a little agitation, this globose fruiting structure breaks apart into a mound of fluff.

Soft, lightweight, fluffy fibers are attached to sycamore seeds. The fibers aid seed dispersal: the lightweight fibers float on wind and water.

A few fruits were picked out of the mound of fluff. The fruits themselves are a type of achene. They aren't showy: they are narrow and measure less than a half inch in length.

You can see leafy, spring-time photos of this specimen on an old blog post, found here.

Tree of the Week: Sycamore (Platanus occidentalis)

There is one sycamore (Platanus occidentalis) in the arboretum collection, and it is pictured above, center. Jeff Trahan collected this specimen from C. Bickham Dickson Park, in south Shreveport. In October of 1996, the 4½ foot tree was initially planted in the grounds of the arboretum. It didn't stay in the ground long. Due to campus renovation projects, the young sycamore was dug up and potted in April of 1999. The following year, in April, it was replanted in the arboretum by Chris Martin, in celebration of Earth Day 2000. 

This is a tough tree! The photo above shows that it's fast-growing, too.

This week, the soft, light-colored, new leaves of the sycamore are of special interest.

The sycamore is a deciduous tree, so all of its leaves are new for the season, but the freshest leaves are pale green and feel like velvet.

This tiny, new leaf is almost white! Despite its small size, the little leaf has the characteristic sycamore leaf-shape: lobed, with incised edges, and slightly wider than it is long.

The larger, more mature leaves are soft and fuzzy, too. The top surface loses its fuzziness during the summer.

Underneath, leaves are covered in white fibers.

Sycamores have big leaves and long petioles. These leaves provide much appreciated shade on those sunny, summer days.

The leaf itself measures over 6 inches in length.

Sycamore leaves are slightly wider than they are long. This leaf measures more than 7 inches wide.

Toward the base of the trunk, the bark is dark, rough, and ridged.

By comparison, bark further up the trunk is thin and flaky. We expect to see more of the light-colored inner bark over the course of the summer.

Sources vary concerning the commonality of surface roots, but this particular sycamore has noticeable surface roots.

In this location of the arboretum, these roots aren't too much of a nuisance, but as you can see in the photo, this root has suffered damage, most likely from a mower.

Sycamore surface root

You can find more pictures of the arboretum's sycamore here.

For more information about this species consult the following:
United States Department of Agriculture
Louisiana Plant Identification and Interactive Virtual Tours
University of Florida IFAS Extension 

Platanus occidentalis