Ramble Report September 29 2016

Today's Ramble was lead by Dale Hoyt.

Here's the link to Don's Facebook album for today's Ramble. (All the photos in this post are compliments of Don. Don also has some really nice butterfly photos here.)

Today's post was written by Dale Hoyt.

Attendees: 28

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Today's reading: Our poet laureate, Robert Ambrose, Jr.,  graced us with a new poem today:

 A Dream on Reading Bertram

I only have to shut my eyes to see 

a Southern piedmont stream run free and clear 

from misty heights and hills of Cherokee 

through crystal pools and glistening shoals; to hear 

the timid whispered hymn of rills and runs 

that trickle gently through the ancient glades; 

to savor the scent of flowering shrubs 

framed by the flaming azaleas of May. 

His world is gone. English ivy creeps from lawns 

to strangle tame suburban trees. Chinese privet 

crowds the sills of clay-stained streams. Kudzu 

casts a tangled shroud across the red eroded hills. 

You wonder - what would Bartram think if he 

could only see? But tell me - what should we?

Today's route: From the Arbor through the Shade Garden via the cement walkway, then across the road to the White trail which we took to the power line and turned left (downhill), crossing the road again and stopping short of the old deer fence. We then returned to the Arbor up the access road and cement walkway.

 

How to find information in a previous blog post. There is an easy way to search all our blog posts for specific items. For example, suppose you want to find the posts where Hurricane lilies are discussed. Open the Google search page and enter the following in the search box:

site:http://naturerambling.blogspot.com hurricane

Google will display all our blog posts that contain the word hurricane. (Make sure you type "site:http" and not "site: http" – "site:" must not be followed by a space or the search won't work. The search is not case sensitive.)

At the Arbor: I originally planned to look for grasshoppers and katydids today, but the cool weather in the forecast made it unlikely that we would find any. Yesterday afternoon I caught a few examples and passed them around.

Barbara had a picture on her cell phone of a large caterpillar (a tomato hornworm) with lots of small, ovoid silk structures on its back. The caterpillar had been attacked by a parasitic wasp that laid an egg in its body. As the egg developed it fissioned into hundreds of identical copies -- like the formation of identical twins in humans, but on steroids.  Each of the clones developed further into a grub-like larva that fed on the internal organs of their host caterpillar. When they reached the size to pupate they chewed their way out through the skin of the caterpillar and spun a silken cocoon within which they formed a pupal stage. After a short period of time a tiny wasp emerged from each cocoon. The caterpillar host usually does not survive.

White trail: We stopped to look at the Carolina Buckthorn berries. A few weeks ago I was fooled by the red berries and misidentified this tree as a deciduous holly. But now the berries are ripening and they become black or a very dark purple. (Holly berries stay red.) Further on we saw another, much larger, buckthorn tree.

Sun and shade leaves of White Oak

Shade and sun leaves. Jeff noticed a couple of White Oak leaves that differed in shape and told us about the adaptive nature of the difference. One leaf was very deeply lobed, the other much less so. The leaf with deeper lobes is found higher in the tree where it is more exposed to the wind. The lobes allow the leaf to fold in high winds and resist tearing better.

There are other differences between leaves on the same tree. Those that are higher in the tree or at the ends of branches are exposed to more intense sunlight than leaves that grow on lower branches or the interior of the tree. Leaves growing where the light is most intense are called "sun leaves" and are narrower but thicker and usually a darker green color. Leaves growing in shadier regions are called "shade leaves" and are broader and thinner. The difference in thickness between sun and shade leaves is due to more layers of photosynthetic cells in the sun leaves. In the shade the light intensity is much lower and the leaf is broader to capture as much sunlight as possible. It is thinner because there is only a single layer of photosynthetic cells.

Modularity in plants: One fundamental way that plants differ from animals is in their modular construction. A plant is literally a collection of similar modules. This fundamental module consists of a node made of one or more leaves or leaf-derived structures (e.g., tendrils). At the base of each leaf is a bud. Nodes are separated by an internode, the portion of the stem or twig lacking nodes. Taken together, the internode and node are the module from which a plant is constructed. These modules are semi-independent even though they obviously interact with each other (the leaves make sugar from sunlight and carbon dioxide and share that sugar with other modules). One way in which the modules interact is seen in the phenomenon of apical dominance. In a tree there is usually only one leader, the shoot that grows straight up. If you cut the leader off its role is take over by a bud in a module close to the top. It begins to grow upward, taking the place of the removed leader. But why didn't it grow upwards before? The leader produces a plant hormone that travels through the vascular system to other modules. This hormone inhibits the growth of the buds in those modules, thus creating the phenomenon we call apical dominance. (The principal hormone that effects apical dominance is called auxin. Its existence was first discovered by Charles Darwin who conducted experiments with his son.)

The Hop hornbeam is a small, understory tree, one of the commonest understory trees in the Garden. By this time of the year its fruits are ripe, but look nothing like what we usually think of as fruits. That's because the botanical definition of a fruit is not just based on what humans eat. A fruit consists of a seed or seeds plus the ovary in which they develop and any other parts that are attached. So the fruit is really part of the flower. Each fruit of the Hop hornbeam consists of a small, papery sac within which is a single seed. If the tree is growing near a stream when its fruit falls into the water the sac provides flotation and carries the fruit downstream, dispersing the seed. There must be other methods of dispersal because Hop hornbeam is found all over the Garden in areas remote from any creeks or other water.

Banded tussock moth caterpillar
On Hop hornbeam leaf

Heterocampa moth caterpillar
Guarding a parasite cocoon??

Caterpillars

We found two different caterpillars on the Hop hornbeam: a Banded tussock moth and a tentatively identified Wavy-lined heterocampa. One online definition of the word "tussock" is: "a small area of grass that is thicker or longer than the grass growing around it." When applied to the caterpillar it is the clumps of hair or bristles that is referred to. Many unrelated caterpillars are decorated with clumps of hair or bristles and several of these can be stinging or irritating, causing a mild itch. To be on the cautious side you should avoid handling such caterpillars unless you are certain that they will be harmless (like the orange and red wooly bear caterpillar often seen this time of year).

The Heterocampa caterpillar is a leaf mimic. The dark areas on its side resemble damaged areas of a leaf and break up the outline of the caterpillar. This individual was immobile and it's not clear why. There is a mound of silk that it is gripping with its abdominal prolegs. (Prolegs are not true, segmented legs like those on the thorax. They are fleshy protuberances from the abdominal segments that are lost during metamorphosis.) This mound of silk reminds me of the cocoons formed by some parasites, similar to the ones that Barbara showed to us at the beginning of the Ramble today. Why the caterpillar is gripping the silk is a mystery, but it reminded me of a study published several years ago. The researchers found a parasitic wasp, Dinocampus coccinellae, that parasitizes Ladybugs. After consuming part of the ladybug the parasite eats it way out of the abdomen and forms a cocoon beneath the ladybug. The ladybug is not dead, but it cannot move. It stands in place, the cocoon beneath it. If it is approached by potential predators it twitches its legs, apparently protecting the parasite that just ate part of its body. There is even more to this story – the paralysis of the ladybug is caused by a virus carried by the parasite. You can read more about this fiendish parasite here. To be honest, I don't know if this caterpillar is involved in a similar situation.

The Maltese Cross shaped leaves of Post oak

The Post Oak is a member of the White Oak group. It has rot-resistant wood and in the past was a popular choice for fence posts. Its leaves have a unique shape, like a Maltese cross, making it easy to identify (when the leaves are on the tree).

Oak groups:The Oaks in our area can be divided into two groups, the White Oak group and the Red Oak group. Each group has several species, leading to some confusion about whether you're talking about the White Oak species (Quercus alba) or White Oak group. Similarly, you could be talking about the Red Oak species (Quercus rubra) or the Red Oak group. If you're in doubt ask for a clarification.

All the White Oak group members have leaves with rounded lobes that lack sharp points at the end of the lobe. White Oak group acorns mature in one year and are "sweet," meaning that they are low in bitter compounds called tannins. Local trees that are in the White Oak group are: White Oak, Chestnut Oak and Swamp Chestnut Oak.

Trees of the Red Oak group have sharp pointed lobes. Their acorns take two years to mature and contain high concentrations of tannins, making the inedible without processing. Examples of Red Oak group species are: Southern Red Oak, Scarlet Oak, Northern Red Oak, Black Oak and Water Oak.

Green ash; note the seeds on left and the two terminal compound leaves arising on opposite sides fo the twig.

Overhead we noticed a Green Ash still retaining some seeds. Ash seeds resemble Maple seeds, consisting of a seed with an attached wing and makes it spin when it falls off the tree. The ash seed has a symmetrical wing (the maple seed is asymmetrical.) Ash leaves are compound, having several leaflets, and oppositely arranged. (You can see that opposite arrangement in Don's photo.)

Flowers of the Beefsteak plant

The Beefsteak plant is regarded by Gary and Linda as an emerging invasive species. We noticed this plant last week and today Sue became model Weed Warrior and started to pull all the Beefsteak plants up. Several other Ramblers joined it.

Square stems and opposite leaves are characteristic of the Mint family plants like this Beefsteak plant.

Mint family characteristics: Invasive or not, the Beefsteak plant exhibits all the characteristic features of the Mint family: it has square stems and opposite leaves.

The flower heads of Wingstem (Verbesina alternifolia)
Note the number of ray and disk flowers and compare to Yellow Crownbeard

The flower heads of Yellow Crownbeard (V. occidentalis)
Note the number of ray and disk flowers and compare to Wingstem

The opposite leaves of Yellow Crownbeard (V. occidentalis)

Wing stems: To a casual observer the Wing stems dominate the lower part of the power line. There are, to be sure, other kinds of plants growing here but the yep yellow flowered wing stems are far and away the most numerous. (A third kind of wing stem, the white flowered Frostweed is now setting seed and no longer blooming.) The two yellow flowered species are easily told apart by the arrangement of their leaves: Yellow Crownbeard has opposite leaves and Wingstem has alternate leaves. Those are simply the diagnostic characters – the features that are most obvious and easily described that differentiate the two species. But we would like to be able to recognize these plants, not just identify them. (For an explanation of the difference see the reading from the Sept. 1 Ramble Report.) Another difference between these species is the shape of the leaves: Yellow Crownbeard has leaves shaped like an arrow-head whereas Wing stem has long, narrow leaves. The flowers are also different. These plants are composites – members of the aster family. The flowers of this family are really groups of smaller flowers that are differentiated into two types: ray flowers and disk flowers. The ray flowers have an elongated and enlarged, strap-like petal that serves as a flag to attract insects to the flower head. The ray flowers are sterile and don't produce seed. The other type of flower is called the disk flower and it makes up the center of the flower head. These are the flowers that will each, if fertilized, produce a single seed. In both species these flowers stick up like tiny, greenish spikes, and Wing stem has more of them than Yellow Crownbeard. The next time you're in the power line you should count them on both species to see how different they are. You should also determine how many ray flowers each species has. Extra credit will be given.

Other plants:

Yellow Indian grass:

Yellow Indian grass

Silver plume grass:

Silver plume grass

Late-flowering thoroughwort:

 

Late-flowering thoroughwort

The name thoroughwort is derived from the older English word meaning through. This spelling is preserved in words such as "thoroughfare," which means a road that goes directly through a town. Some of the thoroughworts have stems that appear to go through the leaves.

SUMMARY OF OBSERVED SPECIES:

Common Name	Scientific Name
Sleepy orange butterfly	Abeis nicippe
Surprise/hurricane lily	Lycoris radiata
Oyster mushrooms	Pleurotus ostreatus
Carolina buckthorn	Frangula caroliniana
White oak	Quercus alba
Tulip tree	Liriodendron tulipifera
Yellow crownbeard	Verbesina occidentalis
Bumblebee	Bombus sp.
Honeybee	Apis mellifera
Post oak	Quercus stellata
Hophornbeam	Ostrya virginiana
Banded tussock moth caterpillar	Halysidota tessellaris
Wavy-lined heterocampa	Heterocampa biundata
Green ash	Fraxinus pennsylvanica
Bitterweed	Helenium amarum
Perilla mint	Perilla frutescens
Fountain grass	Pennisetum setaceum
Poison ivy	Toxicodendron radicans
Wingstem	Verbesina alternifolia
Ailanthus webworm moth	Atteva aurea
Trumpet vine	Campsis radicans
Princess tree	Paulownia tomentosa
Silver leaf elaeagnus	Elaeagnus umbellata
Common camphorweed	Heterotheca subaxillaris
Leafy elephant's foot	Elephantopus carolinianus
Yellow Indian grass	Sorghastrum nutans
Silver plume grass	Saccharum alopecuroides
Gulf fritillary butterfly	Agraulis vanillae
Mistflower	Conoclinium coelestinum
Tiger swallowtail butterfly	Papilio glaucus
Rough-leaf sunflower	Helianthus strumosus
Pennsylvania smartweed	Polygonum pensylvanicum
Late flowering thoroughwort	Eupatorium serotinum
Passionflower vine	Passiflora incarnata
Variegated fritillary (caterpillar)	Euptoieta claudia