Big-Leaf Magnolia (Magnolia macrophylla)

The big-leaf magnolia (Magnolia macrophylla) is blooming this week.

The trunk and branches are spindly. The leaves and flowers are big! You will need to gently pull the leaves down to get a better look at the beautiful flower.

Flowers petals are long, large and droopy.

The flowers are brilliantly white, but for a short while. It seems like this flower lasted only a single day before yellowing. There are more buds higher up, but a ladder would be necessary for studying the flowers, as the leaves mostly obscure the blooms.

Giant Coneflower (Rudbeckia maxima)

In the spring of 2021, a small herbaceous bed was established using young plants collected from rural Caddo parish. Four different species were collected: giant coneflower (Rudbeckia maxima), purple cone-flower (Echinacea sp.), bee balm (Monarda sp.), and boneset (Eupatorium sp.). They were planted near the brick retaining wall that separates the arboretum from Hamilton Hall. This spot is at the top of a gradual slope. It's shaded in the morning and evening, but full sun during the hottest part of the day, and like most of the arboretum, this area is irrigated. One woody plant, a short golden St. John's wort (Hypericum frondosum), was planted along with the herbaceous wildflowers.

Within the two-year time frame, none of the original plantings died and none of them have threatened to 'take over' the allotted space. Today, the giant coneflower and golden St. John's wort are both showcasing beautiful yellow flowers. All photos below are of the giant coneflower.

 

Here we see three giant coneflower flowers with the brick retaining wall serving as a backdrop. These flowers are supported by tall, sturdy stalks.

Note the angle of the photograph: we see underneath the flower because the photographer is only 5'3'', and a stepladder was not used for the photoshoot.

 

Rudbeckia maxima, flower, photographed late May

Rudbeckia maxima, flower, photographed late May

The flower stalks have a few leaves.

Giant coneflower plants have large, blue-green leaves.

Here we see the giant coneflower foliage: big, floppy, cabbage-like leaves.

Rudbeckia maxima, leaves, photographed late May

 

Rudbeckia maxima, leaf, photographed late May

 

This leaf was snipped from the ground, not from the flower stalk. The leaves forming the base of the plant are long, and the leafstalks are long, too.

 

This leaf measures approximately 9 inches in length. Margins are wavy.

 

 

 

 

 

 

 

Pokeweed (Phytolacca americana)

 

At the bottom of the arboretum drainage near the Fitness Center, an interesting, potentially poisonous weed popped up in a bed devoted to a few fringe trees (Chionanthus virginicus). The weed rapidly grew, started flowering, and producing fruits. That's a rapid colonizer.

This is pokeweed (Phytolacca americana), a local favorite, celebrated each year in Blanchard at the Poke Salad Festival. This was formerly a very important species in this area, so it's worth paying attention to. It volunteered in a sunny, wet location, next to the concrete channel that runs under the Fitness Center ramp. This is a relatively small pokeweed plant, only standing about two feet tall. Other individuals of this species can grow several feet high.

 

In the photograph, we see one long raceme with a few white flowers and two developing white racemes.

  

The green, rounded structures are immature fruits. They are expected to turn dark purple or black. Unfortunately, these photos do not capture the characteristic pink-purple stems. If our volunteer pokeweed stays in the game, more photos will be posted.

Tree of the Week: Honey Locust (Gleditsia triacanthos)

The arboretum's lone honey locust (Gleditsia triacanthos) is looking all grown up. This is an 8-year-old tree that germinated in the campus greenhouse from seed collected in Caddo Parish. Upon collection the species was not known for certain, but we are now confident that this is a honey locust.

Our honey locust grows in the middle of a gradual slope; not at the top of the hill and not at the bottom. Pictured in the background, we see the red bricks of Cline Hall dormitory, currently being remodeled.

Much of the new growth is now out of reach. The youngest leaves are red and orange. Don't worry, they're fine.

For the first several years, this specimen had long, skinny, flopping branches that refused to stay upright. Regular pruning and staking were required to develop a straight trunk, and also to minimize the hazardous nature of the thorny branches.

Toward its base, the trunk is approximately four inches wide and it is heavily protected. Do small animals make useful habitat out of these thorns?

In the arboretum record, this is the first year it has produced flowers. Photographs of the flowers were taken on April 22, 2022.

Pollinators were hard at work.

Small, greenish flowers hang in clusters. These flowers aren't showy, but have a nice fragrance.

You can see more photos of this honey locust on an older blog post, found here.

Climbing Dogbane (Trachelospermum difforme)

Climbing dogbane (Trachelospermum difforme) is a species of vine, native to Louisiana, that volunteers in wet areas of the arboretum. It currently maintains a weedy status, growing not necessarily in the best  places. In the past, it has overtopped the chickasaw plum patch and the large swamp rose bush. It has also been known to climb the swamp titi shrubs along the bank of the upper drainage. Since this vine is aggressive and successful in the soil of the arboretum, it is annually cut back to ensure a competitive advantage for the species that were intentionally planted. 

However, climbing dogbane is a resilient vine that is difficult to remove: you cannot simply pull it loose. Climbing dogbane intricately entwines itself with whatever it can find. As a result, pulling on the vine tends to result in more damage to the host plant rather than the dogbane. Currently, we do not have a specific location for it to grow unhindered. We ought to give some thought to providing a proper place for the dogbane to thrive. For now, we will continue to annually cut it back. 

 Today, we have pictures of a climbing dogbane vine that has made a home in the lead plant shrub (Amorpha paniculata).

 

Climbing dogbane is a woody vine that can be found in wet areas of the arboretum. Its leaves appear in pairs along the slender vine.

A fresh green tendril extends from the red vine. Note: leaves vary in shape along the vine. These leaves have a lanceolate shape.

We see glossy, green climbing dogbane leaves in the foreground. These leaves have an obovate shape.

The tough vine has a red hue.

The obovate leaves have a slightly asymmetrical shape with pointed tips. The upper surface is dark green.

The lower surface is light green.

The larger, mature leaves measure more than 3 inches in length.

Climbing dogbane flowers appear in clusters. They are small, yellow flowers. No fragrance was deteceted; however, the LSU AgCenter claims "very fragrant".

Flowers of the climbing dogbane (Trachelospermum difforme), photographed June 21, 2021

For more information about this species consult the following online sources:

United States Department of Agriculture (zoom in on the distribution map)

Louisiana Plant Identification and Interactive Virtual Tours (LSU AgCenter)