What's in Bloom?

During the long, bright, hot, dry days of summer splendid orange flowers can be found throughout Louisiana, blooming under the harshest conditions, unfurling like trumpets sounding out through the green. Trumpet creeper vine (Campsis radicans) flourishes in the arboretum. It grows as a volunteer and steadily tries to invade and conquer new territory.

These tropical delights are known to cause skin irritation for some, so pluck and handle with care!

Pictured above, trumpet creeper vine (Campsis radicans) blooms along the red brick retaining wall between Hamilton Hall and Mickle Hall. The above photographs were taken during June 2020.

Tree of the Week: Catalpa (Catalpa bignonioides)

The catalpa trees are of special interest this week. Their long, skinny, conspicuous fruits are ripening.

The 'Indian cigars' or 'bean pods' are drying out, turning from green to brown, and starting to split open, revealing their seeds. If you're interested in growing your own fish bait tree, be on the look-out this time of year. Of course, if you are nearby, come down to the arboretum and take an Indian cigar home with you. Make sure you get a brown and brittle one!

These are truly long fruits. Unfortunately the foot-long ruler isn't up to the task of measuring the length. Let's just say the fruits are well over a foot, and possibly as long as two feet.

On the outside, the fruits have a grooved texture that runs the length of the capsule.

When the fruit dries, it becomes brittle and splits along those grooves. This brown seedpod was cut from the tree intact. Applying a little pressure, it popped open. Some seeds readily dislodged from the fruit.

Seeds might dislodge from the capsule wall, and then dangle for some time, blowing in the wind.

Other seeds remain attached to the inside wall of the capsule, and, presumably, would dislodge of their own accord over time. As a result, seed dispersal doesn't occur all at once. For the best opportunity to grow your own fish bait tree, the USDA recommends waiting until winter or early spring to collect catalpa seeds, as the seedpods are expected to remain attached to the tree throughout fall and winter. But, of course, you could collect seeds now, and then try again in the spring, too.

Seeds are concealed in a white, papery fiber resembling wings, which suggests wind dispersal. It wasn't tested for this photo shoot, but presumably the light-weight fiber floats on water, too.

The seed covering isn't easy to remove. Leave it on for germination.

Without their wings, seeds measure approximately ½ inch in length.

Tree of the Week: Catalpa (Catalpa bignonioides)

Less than a month ago we were admiring the pretty white flowers of the catalpa trees (Catalpa bignonioides). Of the two individuals in the arboretum collection, we focused on the the larger individual for our tree of the week post. The smaller tree also had flowers at the time, and, today, both trees have the conspicuous 'Indian cigars,' or bean pods, hanging from their branches. This week we have photos of the smaller catalpa specimen. It is of special interest because it is playing host to the famous 'catawba worm'.

This catalpa is less than 5 years old. It germinated in the campus greenhouse from seeds collected at an old homestead outside Springhill, Louisiana. In 2015, it was planted in the arboretum, at the bottom of a steep slope near the Fitness Center.

The long, slender catalpa fruits are already noticeable, hanging from the branches.

The seedpods are very long, measuring approximately 16 inches. The fruits aren't ripe yet; they will most likely increase in length.

Catalpa leaves are large and heart-shaped. The leaf and the petiole measure over a foot in length.

The underside is light-green and fuzzy.

Some of the leaves have lost there heart shape. The tip of this leaf has been eaten by the catalpa 'catawba' (or even "catawbla") worm (Ceratomia catalpae), who is pictured inching along the leaf midrib.

The caterpillar is greenish-white to yellowish-white with a black head, black spots, and a black spike on the rump. It measures over an inch in length. These worms have a reputation for being a high quality fish bait.

There is variation among the caterpillars: some are more black than white, and their appearance also changes as they grow larger.

We aren't seeing too many caterpillars yet; only a few leaves have been eaten. But these catalpa worms are known to entirely defoliate their hosts, sometimes more than twice a season. If defoliation does occur, new leaves are expected to develop quickly.

For more information about this species consult the following:
United State Department of Agriculture - be sure to zoom in on the distribution map
Auburn University has an informative article about the catalpa worm. You can find it here.

Tree of the Week: Catalpa (Catalpa bignonioides)

The catalpa (Catalpa bignonioides) is flowering this week in the arboretum. The beautiful, fragrant white flowers can be found near the Fitness Center. There are two trees, both located on the northside of the Fitness Center ramp.

The two catalpas are less than five years old. In 2013, seeds were collected from an old homestead near Springhill, Louisiana, and they were immediately potted in the campus greenhouse. The seedlings grew up fast. In 2015, two of the little trees were planted in the arboretum. One tree was planted at the bottom of a gradual slope, and the other tree was planted at the bottom of a very steep slope. Both trees are healthy and blooming wonderfully, but there is a clear size difference. The tree planted at the bottom of the gradual slope is double the size of the other. The photos below were taken of the larger tree.

The catalpa is pictured left of center. A pond cypress (Taxodium ascendens) stands further back, along the concrete drainage. This is a low spot in the arboretum, so whenever it rains, this area stays wet longer. The other catalpa is planted on the opposite side of the concrete drainage, on a much steeper slope, where water quickly runs off.

The catalpa is pictured center. Further back stands a bald cypress (Taxodium distichum), near the Fitness Center ramp. This is the larger of the two catalpas. It is growing tall and staying slender. It has a gangly appearance, with its asymmetrical skinny branches topped with large clumps of leaves. 

Catalpa leaves are big, but they don't hide the branches.

The heart-shaped leaves are very large, measuring over a foot. The topside is dark green with smooth, wavy edges. These pretty green leaves are also known for having an unpleasant odor when crushed. The leaves of this particular tree have a faint polecat odor, only when crushed.

This petiole measures almost 5 inches.

Underneath the leaves are whitish-green.

The underside feels velvety.

Frilly, white trumpet flowers are clustered together on a panicle

Up close we see purple dots and splotches of orange. The flowers also have a pleasant fragrance.

The bark on this 5-year-old specimen is mostly gray and a little rough.

For more information about this species consult the following:
United States Department of Agriculture
Louisiana Plant Identification and Interactive Virtual Tours (LSU AgCenter)
NC State Extension

Bignonia capreolata

Campsis radicans

Bignoniaceae

Bignonia capreolata

Campsis radicans