Friday, June 3, 2016

Ramble Report June 2 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.)
Today's post was written by Dale Hoyt and Don Hunter.

Twenty-one Ramblers met today at 8AM, the meeting time for the rest of the summer. We resume meeting at 8:30AM the first Thursday in September.

Today's reading: Dale read a passage from Lab Girl, by Hope Jahren:

Let's consider a modest, unremarkable tree-the one living on your street, perhaps. A decorative maple tree, about the height of a streetlight . . When the sun is directly overhead, the little maple in our example casts a shadow about the size of a parking space. However, if we pluck off all the leaves and lay them flat, side by side, they would cover three parking spaces. By suspending each leaf separately, the tree has stacked its surface area into a sort of ladder for light to fall down. Looking up, you notice that the leaves at the top of any tree are smaller, on average, than the leaves at the bottom. This allows sunlight to be caught near the base whenever the wind blows and parts the upper branches. Look again and you'll notice that leaves low in the canopy are of a darker green; they contain more of the pigment that helps each leaf absorb sunshine, allowing them to harvest the weaker rays that penetrate shade. When building foliage, a tree must budget for each leaf individually and allocate for each position relative to the other leaves. . . .
The leaves on our little maple, all taken together, weigh thirty-five pounds. Every ounce therein must be pulled from the air or mined from the soil-and quickly-over the course of a few short months. From the atmosphere, a plant gains carbon dioxide, which it will make into sugar and pith. Thirty-five pounds of maple leaves may not taste sweet to you and me, but they actually contain enough sucrose to make three pecan pies, which is the sweetest thing that I can think of right now. The pithy skeleton within the leaves contains enough cellulose to make almost three hundred sheets of paper, which is about the number that I used to print out the manuscript for this book.
Our tree's only source of energy is the sun. . . . The plant pigment chlorophyll is a large molecule, and within the bowl of its spoon-shaped structure sits one single precious magnesium atom. The amount of magnesium needed for enough chlorophyll to fuel thirty-five pounds of leaves is equivalent to the amount of magnesium found in fourteen One A Day vitamins, and it must ultimately dissolve out of bedrock, which is a geologically slow process. Magnesium, phosphorous, iron, and the many other micronutrients that our tree needs can be gained only from the extremely dilute solution that flows in between the tiny mineral grains within the soil. In order to accumulate all of the soil nutrients that thirty-five pounds of leaves require, our tree must first absorb and then evaporate at least eight thousand gallons of water from the soil. That's enough to fill a tanker truck. That's enough to keep twenty-five people alive for a year. That's enough to make you worry about when it is next going to rain.

Today's route: From the Arbor we walked down the mulched path to the Dunson Garden, through the Dunson Garden and down the power line right-of-way to the river. We visited the location where a week ago a River Cooter had laid eggs and then turned around and walked down the Orange trail until we located a flowering Bur Cucumber vine. Then we retraced our steps and adjourned to Donderos'.

Arbor to White connector trail:

We reviewed the trees we identified last week: American Beech, Sourwood, Hophornbeam, Northern Red Oak, White Oak.

A note on how trees grow: if you drive a nail into a tree four feet from the ground and the tree grows 1 foot a year, how high will the nail be in 10 years? If you said 14 feet you were wrong. The nail will remain at 4 feet from the ground. Trees grow in girth but the increase in height is at the top. The twig at the end of the branch grows longer but then ceases growth in length. Each successive year new twigs appear that the ends of their branches and the old part of the twigs grow in diameter only. This is why that branch you climbed on when you were a kid can be enjoyed by your children and grandchildren in exactly the same way.

Susie noticed a large tree/shrub off the trail and wondered if it was one of our native hollies. This close to the formal gardens we sometimes encounter an escaped horticultural variety and this tree looked like that. Its leaves were thin, like the native American Holly, but they were significantly different in shape. I think it is likely a variety or a hybrid between American Holly and cultivated variety.

George noticed a tree off the trail with large leaves and wondered what it was. We could tell that it had pinnately compound leaves with five to seven leaflets but had trouble deciding if they were opposite or alternate. The leaves we could see easily were low on the tree and therefore shade leaves which are usually broader than those further up in the tree, so they may not have been typical. The shape of the leaflets suggested that they were a Hickory, but some people thought that the leaves were opposite. The conclusion: either a young Green Ash or a Hickory. The consensus seemed to be leaning toward Hickory, in which case it was probably Pignut hickory.

Speaking of Ash trees – Barbara wondered if the Emerald Ash Borer had reached Georgia and if it was likely to be in Athens. The Emerald Ash Borer is a beetle that is causing the death of Ash trees all over the northern states. The answer is yes, it has been found in Georgia. Last year the Georgia DNR published a map of counties where the insect had been observed. They were all the counties from Chattanooga to Atlanta that bordered I-75 and all the metro-Atlanta counties. It is only a matter of time before the beetle comes to Clarke county.

Bowl and doily spider web
There was an interesting spider web on the branches of a Hophornbeam. It looked similar to what is normally called a "Bowl and doily" spider web, but it was angled differently. The web consists of a flat orb web and above that a tangle of threads. Insects get trapped in the threads, not because they are sticky, but because they are so closely and randomly packed, like a thicket of silk strands. In struggling to get through the insect gradually falls into the orb web below, where the spider lurks. The tangle of threads slows the prey down and increases the likelihood that they will be captured.

Dunson Native Flora Garden:

Black cohosh flowers
Black Cohosh is blooming, its elegant racemes of white flowers gracefully rising well above the leaves, like flashes of light in the shaded understory.

Some Bloodroot leaves still remain. This plant is one of the first to flower in the late winter/early spring and is often lumped together with the other "spring ephemerals." But, strictly speaking, it is not one. A spring ephemeral flowers before the canopy closes, then produces fruit and disperses its seeds and the above ground parts wither away. Bloodroot leaves remain lush and green well into summer, so it is technically different from the true spring ephemerals. But it doesn't care what we call it.

Several Jacks-in-the-pulpit (or is it Jack-in-the-pulpits?) with five leaves, instead of the more typical three, can be found in the DNFG. Some have developing fruits. The "pulpit" of these plants has withered away and only the spadix and the leaves remain. The spadix is the "jack" – the structure that bore the flowers inside the pulpit (the spath). But we probably ought to find a more sex-neutral name because these plants can be either male or female, depending on the amount of energy they have stored from the previous year of growth. Those with enough stored resources will produce a spadix covered with pistillate (female) flowers; those with fewer resources produce staminate (male). So the same plant may be male one year and female the next, or not even produce a pulpit, depending on the amount of its stored energy. The immature fruit of our plants is now colored green and will mature to a brilliant red when ripe.

Christmas fern
Christmas fern; underneath the fertile portion of the frond
Christmas fern; closup of under surface of a single pinna, showing sporangia
When we stopped to examine a Christmas fern. Ronnie pointed out that the shape of the leaflets (called, in fern-speak, pinnae; pronounced: pin-ee; singular: pinna) was like Santa's boot or the stockings that are hung by the chimney at Christmas time, hence the common name of the plant. In many of the fronds the pinnae on the terminal 1/3 are distinctly smaller and bear brown spore-producing structures on their undersurface. Spores are the means by which ferns disperse into new locations. They are as fine as dust and are produced by the millions. The gentlest of breezes carry them away and, if they are lucky, they will land in an hospitable place and germinate. In this way spores are like the seeds of flowering plants. But seeds carry a plant embryo and nutrients to fuel its early growth. A spore has none of these. It is a single cell and, after germination, it is on its own. It develops chlorophyll and must use sunlight and air to make enough sugar to fuel its further growth. But it doesn't become a fern. Instead it grows into a tiny, flat plant that develops male and female structures on its surface. Sperm produced in the male structures swim over to the female structure and fertilize the egg within it. From this fertilized egg the fern as we know it develops.

Sensitve fern;
sterile fronds are green
fertile fronds dark colored in center

In some ferns the spore bearing fronds are distinct from the other fronds. These are called fertile fronds; those that never develop spore producing structures are called sterile fronds. Examples of ferns that have separate fertile fronds are Sensitive fern, Rattlesnake fern and Cinnamon fern, all of which can be seen in the DNFG.

Ronnie finds a piece of Sycamore bark
American sycamore is one of those trees whose bark changes in character with age. The young tree and bark is smooth and resemble camouflage with its pattern of light gray, green and brown. This bark often flakes off into large pieces, thought by some to be a way of discouraging vines from growing up the trunk. As the tree ages the older bark at the base loses its smooth texture and becomes dark and rough – very different from its youthful appearence.

Spicebush fruit
Earlier this year we found the pair of Spicebush plants in bloom. This is a dioecious species, meaning that each plant bears flowers of a single sex only. One plant has only staminate (male) flowers that produce pollen, while another plant has only pistillate (female) flower that will develop fruits, if pollinated by a nearby male plant. In the DNFG the two sexes are planted next to one another; we saw them flowering earlier in the spring and now the pistillate plant is bearing fruit.

Pipsissewa flower, unlike any other
One of the other delightful surprises in the DNFG was several Pipsissewa (Spotted Wintergreen) in bloom. The waxy, nodding flowers are even more beautiful up close. The wintergreen refers to the fact that the plant retains its leaves throughout winter; it does not have the wintergreen scent. The other name is derived from the word pipisisikweu in one of the Cree Indian languages. It means "it breaks it into small pieces", which refers to the idea that the juice of the plant breaks down kidney stones. It is a diuretic.

Near the bottom of the DNFG is a Painted Buckeye with at least one fruit (spotted by the eagle-eyed George). There are many other Painted Buckeyes that flowered earlier this year but this is the only one that we have seen fruit on.

Yucca flower; pistil is tall structure in the middle
At the very bottom of the DNFG is a group of Yucca filamentosa. Many of the Ramblers remarked that they always thought of Yucca as being a plant only found in the southwestern deserts. Our Yucca's natural range is the southeastern US from Louisiana east to Florida and north to Virginia. But it has been widely cultivated outside this range and become naturalized. In fact, the discoverer of its mutualistic pollination system, Charles Valentine Riley, studied it in the Missouri Botanical Garden in St. Louis, Missouri. The Yucca flower is unusual in that the stigma, the part of the pistil that receives pollen, is concealed in the hollow end of the pistil, away from where a visiting bee might brush pollen on it. Riley, working at night with a kerosene lantern, discovered a small moth that gathered pollen from a Yucca flower and formed it into a small ball with its modified mouth parts. The moth then flew to another plant, entered the flower and laid some eggs on the ovary and then climbed up the pistil and, using its mouthparts, pushed its pollen load into the hollow at the top of the pistil where the stigma is, thus ensuring that there would be developing seeds on which its caterpillar could feed. (Without pollination the flower could not make seeds and the caterpillar would die.) This seems like a simple case of symbiotic mutualism, each party being dependent on the other. But it turns out to be more complicated. What if more moths lay eggs in the same flower? Then all the seeds might be consumed and the plant loses the benefit. It turns out that the plant somehow can sense when there are too many caterpillars and will then abort the flower. There are also cheater species of moths that don't have the necessary mouthparts to collect pollen. They lay their eggs in the Yucca flowers and are totally dependent on the other moth species to pollinate the flower to produce seed.

Cone flower
Next to the Yucca bed is a planting of a type of Cone flower, but its "petals", actually ray florets, are very long and thin, so it is not the common Purple coneflower. None of us know what it is and there was no tag in the planting to help identify it.

Long-leaf pine among the Cone flowers
Growing among the Cone flowers is a young Long-leaf pine, still in the grass stage. Long-leaf pine is a fire adapted species. The first few years after a seed has germinated the pine resembles a clump of grass. All the energy produced by the clump of young pine needles is directed into the growth of the root. At this stage of growth the tip of the tree is tightly nestled at the base of the soil and protected by the dense cluster of pine needles that surround it. If a low-intensity fire should happen it will only singe the needles, leaving the protected apex undamaged. After 5 – 12 years the root system is established and the tree undergoes rapid elongation. Within two years its growing tip is above the fire zone, the height below which it would be damaged by a low intensity fire.

Things that Ronnie found:

Leaf-footed bug
British soldiers lichen
It really helps to have a young person along on these Rambles. Ronnie, our youngest Rambler has keen eyesight and is always finding things of interest. He discovered a beautiful moth, probably in the genus Haploa. It had white forewings that covered the hind wings, forming a triangular shape. The edges of the wings were black and where they met they formed a sword or cross shape. Ronnie dubbed this the "Crusader Moth." He also found Wood ear mushrooms growing on a fallen branch, a spider that left a silken trail as it moved around the vial we placed it in, an Eastern leaf-footed bug, found on the Yucca blossoms, British soldiers lichens growing between the boards of a small bridge at the edge of the garden and, lastly, a large piece of bark shed by the Sycamore tree. Good job, Ronnie!

White Trail in ROW:

The dense growth of plants that inhabit the flood plain of the power line right-of-way is starting to take off. Some of the summer flowering species have begun to bloom, but most are still growing vegetatively. Some of the Pokeweed bears a few skimpy inflorescences, none in flower yet.

Wild Petunia
Next to the path through the ROW we found the first flowers of Wild Petunia and Common yellow wood sorrel. There are three species of Verbesina growing here, collectively known as Wingstems, because of the thin ridges that run the length of their stems. Each of these species has its own common name that often doesn't contain "wingstem." One that is particularly abundant has opposite leaves and will develop yellow flowers later – it's called Yellow crownbeard. Also present are Rough sunflower, Ironweed and Goldenrod.

Goldenrod apical leaf gall

Goldenrod spherical gall
Among the Goldenrods we looked for the galls that are caused by three different insects, but only found two types. The galls are produced by feeding of insect larvae within the tissue of the plant stem. An egg is laid on the growing tip of the plant and, when it hatches, the larva tunnels into the stem tissue. In one case, as tiny fly lays its egg on the tip of the Goldenrod and the activity of the larva inhibits the elongation of the internodes, creating a clump of leaves at the end of the stem that looks like a ratty green corsage. Another kind of fly larva produces a hard, spherical swelling in the stem. Yet a third type, that we didn't see today, is made by a moth, whose larva causes a spindle-shaped gall to form.

Green Ash with fruits (seeds)
To the west of ROW someone spotted a tall tree with what appeared to be masses of yellow flowers. Examination of the "flowers" with binoculars revealed that they were masses of seeds, the fruits of a Green Ash tree.

Another surprise was the discovery of an orange
Dodder tapping into its host plant
colored cord that is really a plant that lacks chlorophyll and is a parasite on other flowering plants – Dodder. The Dodder vines twist about their victim and wherever the vine touches the host it penetrates the skin and invades the plant circulatory system inside, stealing the sap for its own usage. Dodder is a flowering plant in the Morning Glory family.

When we hit the river we took a short detour to the location where last week Emily and I watched a large River Cooter (a kind of turtle) excavating a nest. As we watched she dug a nest, mostly with one hind foot, and then dropped 15 eggs into the hole she had dug. Then she proceeded to fill the hole, again using just one hind leg. We left before she finished and we wanted to see if we could detect any sign of the nest. Pushing aside the grasses we found only a patch of sandy dirt with no discernible sign that anything had happened there. We replaced the grasses and resumed our ramble on the Orange trail.

Orange Trail, south of ROW:

Bur Cucumber flowers

Bur Cucumber spiny fruits
We moved downstream on the Orange trail, looking for the vines of Bur Cucumber that were blooming or had fruit. We found both clambering up a small Box Elder so we took a look at the variable leaves of the tree. Some of the leaves have only three leaflets and others five.

On the way back Ronnie found a caterpillar that looked like a brown wooly bear. It is probably the larva of a moth in the Tiger moth family, but that is only a partially educated guess.

Then it was back to Donderos' for our customary conversation and drink.

American beech
Fagus grandifolia
Superfamily Curculionoidea
Oxydendron aboreum
White oak
Quercus alba
Ilex sp.
Ostrya virginiana
Poison ivy
Toxicodendron radicans
Pignut hickory
Carya glabra
Northern red oak
Quercus rubra
Green ash
Fraxinus pennsylvanica
Black cohosh
Actaea racemosa
Wood ear mushrooms
Auricularia auricula
Spider, not specified
Christmas fern
Polystichum acrostichoides
Sensitive fern
Onoclea sensibilis
Rattlesnake fern
Botrychium virginianum
American sycamore
Platanus occidentalis
Lindera benzoin
Spotted wintergreen
Chimaphila maculata
Aesculus sp.
Yucca filamentosa
Eastern leaf-footed bug
Leptoglossus phyllopus
Smooth purple coneflower (?)
Echinacea laevigata
Longleaf pine
Pinus palustris
Baptisia sp.
British soldier lichens
Cladonia cristatella
American pokeweed
Phytolacca americana
Common yellow wood sorrel
Oxalis stricta
Wild petunia
Ruellia caroliniensis
Yellow crownbeard
Verbesina occidentalis
Rough sunflower
Helianthus hirsutus
Solidago altissima
Common dodder
Cuscuta gronovii
Eastern river cooter
Pseudemys concinna
Bur cucumber
Sicyos angulatus
Box elder
Acer negundo
Tiger moth caterpillar
Lepidoptera: Family Erebidae
Subfamily Arctiinae

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