March Blooms in the Arboretum

Spring doesn't officially begin until the vernal equinox, which is still about two weeks away. But the weather, the animals, and the plants have decided that, for us in Shreveport, the season has arrived in advance of its astronomical formalities. 

Glorious flowering from our Mexican plums (Prunus mexicana) this week.

 

At this time, the flowers have a powerful, distinct, and not altogether pleasant aroma.  Nature's a funny thing.

Here we have a post from March 2019 featuring the same delightful Mexican plum blossoms. And a post from this time last year showing our efforts to transplant some new Mexican plums. Leafing-out season will tell us if that was successful.

Elsewhere in the arboretum, you can find flowers of the paw paw (Asimina triloba). These are less-showy. You will need to go looking for these along the drainage channel that runs north to south through the arboretum.

The juxtaposition of these deep crimson-purple bells alongside the green bells is unforgettable.

We attempted some cross-pollination. Good luck, little tree.

See our post from last summer on planting new paw paw and a similar springtime post from 2022 that features paw paw flowers.

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.

Tree Removal: Pawpaw, Sweetgum, Mulberry

Today we continued normal cleanup operations in the Arboretum. This customarily involves cleaning up the paths, picking up fallen limbs, moving gravel around, and today a special task: cutting down some trees and removing stumps.

First, a water leak in the arboretum, down the slope from Mickle Hall, required a lot of dirt work. This area is in shambles, but there is really no alternative. Our native clay can be quite an adversary. Don't try to walk through this area; just go around.

Onto the main tasks.... Here is a sweetgum (Liquidambar styraciflua) stump, which you can see on an earlier blogpost here. In that post we said "Now all that remains is a two-foot stump which will be removed at a later date." That day has arrived.

Resprouting, this tree is still alive. This photo was taken after all of the new growth was trimmed.

Afterwards, we have a more-or-less flat area that will not be a tripping hazard. The roots were not removed, which means that we have not yet seen the end of sweetgum shoots.

Next we have a highly suspect pawpaw (Asimina triloba), which you can read more about on an earlier blog post, here. This tree has had a broken crown for nearly a decade, which may have led to some health problems. Recently it has taken a turn for the worst, so now we must make an assessment. Before we cut the tree down, let's inspect the specimen to determine its condition.

 

The bare pawpaw trunk is pictured center. Louisiana palmettos and titi shrubs are in the background.

This image becomes more unsettling the longer you look at it. Here you can see fungal pink slime oozing from the bark and forming bubbles. What on earth is this?

This rotten branch nub was characteristic of the whole tree.

Scoring thin bark will often reveal healthy green cambium underneath. Scoring this pawpaw revealed dead tissue and only excited the ants and other bugs crawling across it. Snapping a few twigs, which should have been green and springy, verified that this tree is completely dead. Cutting it down released a horrendous mushroom-like smell.

All gone, and only a few blog posts to tell the tale.

This cross section reveals a rotten tree. It may not be immediately obvious from this photo, but the inner rings of the tree were sickly green and oozed.

The lower feet of the trunk served as a nursery for untold billions of fungal spores and the entire surface of the bark had turned green. The white specks were tubular filaments rising off the surface of the bark and ending in a nodule.

Finally, this undesirable specimen is a hybrid of Morus rubra, the red mulberry, and an Asian species. Since we want to preserve native species, we will remove this one as we have removed other white-berried and black-berried mulberries in the arboretum.

We see leaves of the characteristically variable Morus genus.

Our mulberry hybrid was dissassembled.

This area is already a major tripping hazard due to holes and uneven ground, so we've sawed the stump down as low as possible. Cutting around soil will quickly dull your chainsaw blade, but there's no helping it.

Autumn is a great time of the year for these kinds of clean-up operations. Look around and you'll find plenty of work to do!

Springtime in the Arboretum

Spring is officially here, having begun on March 20th, and many of the inhabitants of the arboretum are in full vigor. A walk through will reveal a variety of species putting out new leaves, putting on flowers, performing reproduction, and otherwise enjoying the change in seasons.

These are samaras of the red maple (Acer rubrum).

Here we see flowers of the devilwood (Osmanthus americanus).

Laurel cherry (Prunus caroliniana) flowers are numerous!

These are purple pawpaw (Asimina triloba) flowers.

These are green pawpaw flowers. They will soon turn maroon or purple.

This pretty little white flower is produced by the mayhaw (Crataegus opaca). Last spring, an eastern red cedar was cut down in the hopes that we would see more of these flowers. As compared with the last three years, we are certainly seeing more mayhaw flowers today.

In northwest Louisiana, we love our azaleas, but not all azaleas are native to the southeastern United States. Here we have the stunning flowers of our native yellow-flowered azalea (Rhododendron austrinum).

 

 

 

Tree of the Week: Pawpaw (Asimina triloba)

One pawpaw fruit was spotted today. The developing green fruit blends in with the surrounding vegetation. Can you see it?

This single fruit is exciting, but also a little sad. There are several tall, mature papaw trees cohabitating along the stream. The trees are known for flowering nicely; evidence can be found on the blog post from last spring (here). Unfortunately, we never see any fruits.

Since we have three pawpaw volunteers in the collection, the mature trees must have successfully reproduced in the past. Fruits are simply few and far between. How do we make more?

Tree of the Week: Pawpaw (Asimina triloba)

Our tree of the week is pictured center. Its straight, gray trunk is flanked by two arboretum signs. This pawpaw (Asimina triloba) grows in a low, wet area of the arboretum, among Louisiana palmettos, horsetail, and swamp titi bushes. A volunteer red buckeye can also be spied in the photo.

During the fall semester of 1994, Professor Ed Leuck collected this pawpaw from Caney Lake, north of Minden, Louisiana. Professor Leuck nurtured the young tree in a container for some time before moving it to its present location in Feb. 1996. Over the past two decades the pawpaw has developed nicely, but unfortunately we do not have any notes in the arboretum catalogue concerning its fruit production. Pawpaws are known for their tasty fruits, so we will be keeping an eye on this individual, and its kin, over the next several months.

The bark of this 25-year-old pawpaw is light gray and slightly rough

During the first week of spring, we have noticed flowers and new leaves. Do pardon the light dusting of pollen; the trees in the arboretum are hard at work.

The purple pawpaw flowers hang down, resembling bells. They have an interesting, hard-to-identify fragrance, which is neither good nor bad. Note the purple hairs on the green flower stalk; the new leaves are fuzzy, too.

From below, we can see that each flower has 6 petals that are varying shades of red-purple.

A few twigs were snipped for closer inspection.

Pawpaw flowers appear singly or in clusters. In this case, we have three flowers in different stages of development on one twig.

Pawpaw flowers are more than an inch in length.

Each pawpaw bell has three purplish-green sepals.

For the past week, a fine golden dust has covered nearly all of northwest Louisiana. The upturned pawpaw bell is no exception.

You can find a few more pictures of this pawpaw tree here.


For more information about this species consult the following:
Louisiana Plant Identification and Interactive Virtual Tours (LSU AgCenter)
United States Department of Agriculture
University of Kentucky
U.S. Forest Service

Asimina triloba