Ramble Report April 18 2019

Today's Ramble was led 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, unless otherwise credited.)

Today's post was written by Dale Hoyt.

Today’s Focus: Looking at how trees grow.

22 Ramblers met today.

Announcements:

1. Eugenia said the Georgia DOT has decided to purchase native and locally grown plants, where possible, for their highway beautification projects, according to the latest Farmer's Market Bulletin.
2. Jess Riddle will be at the local Barnes and Noble bookstore tonight (4/18) at 7:00 p.m., to sign his book, Mountain Treasures, about old growth forest in unprotected wild lands.
3. Jess Riddle will also be speaking next Thursday, May 2, at the Oconee Rivers Audubon Society meeting. 
4. Linda wants to share this posthumously published piece by Oliver Sacks: The Healing Power of Gardens.

Today's reading: No reading today

Show and Tell: Dale passed around a twig from a Northern Red Oak tree. The new growth from the apical bud was still green. More about this and why it was detached from the tree later in the report.

Today's route: Through the conservatory and formal garden to the Purple Trail, then Purple Trail to the Hi Water Trail. Hi Water Trail to Orange Trail and then left on the Orange Trail back to the Visitor Center.

Tip for viewing photos in this blog: If you left click on any photo in this post it will pop up in its original, larger size! Below this enlarged photo you will find a row of thumbnail photos for all the photos in the blog post. This really helps if you'd like to see larger images for more detail.
(This works for me on my desktop Windows PC.)


How trees grow:

Northern Red Oak; new shoot; note the dark lateral buds where the leaf stems attach to the green stem of the new shoot.

The photo above is a Northern Red Oak twig that we found on the ground. Notice that the new growth emerges from the end of last years twig, which is brown in color. This new “shoot” emerged from a bud at the very end of the twig, which was last year’s new shoot. If you could examine every twig on the tree two weeks ago you would find a small, dark bud, covered with bud scales. Since last week the scales on the terminal buds have all fallen off and the tiny shoots that were protected by the bud scales are rapidly elongating and expanding. Each new shoot is a green twig with a variable number of leaves. At the place where each of these leaves is attached to the twig (the leaf’s axil) there is a new bud, called a lateral bud, because it is on the side of the twig and not the end. The bud on the end of the new shoot is called the terminal bud. Inside these buds shoots are beginning to develop – the shoots for next years growth. The lateral buds contain either a leaf, a flower or a shoot. If the lateral bud contains a shoot and the bud germinates it will make a new branch. In the photo above you can see the new lateral buds in the axils of the leaves. They are the dark dots where the leaf stems attach to the shoot.

In many trees this elongation of the new shoot is the only time when the tree grows during the year. Every branch and twig grows by adding a new shoot at the end and that year’s growth ceases when the shoot stops elongating.

When the terminal bud scales drop off the shoot they leave a scar and by looking back on the twig you can find similar scars and determine how much the twig grew for several years. But, as the twig elongates, it also increases in diameter and expansion gradually erases the older terminal bud scale scars. Therefore, you can only trace the growth for two or three years.

In some trees the shoot growth is not completely preformed. Instead, the new shoot can continue producing leaves at its terminal bud.

Hop Hornbeam terminal leaves on a new shoot; note lack of a terminal bud and the presence of new leaves. The white spot of the tiny leaf to the left is another, even smaller, leaf.

An example of this type of growth can be seen in the Hop Hornbeam where the terminal bud continues to produce leaves. This type of growth occurs over a longer period of time and is limited by the availability of external resources.

LIST OF OBSERVATIONS:

Purple Trail:

Developing Blueberries

The Highbush Blueberry is nearly finished blooming and berries in various stages of development are still green.

Gray Squirrel with a late morning snack

A Gray Squirrel was happily grazing on the Wood Rush seeds growing on the roof of the little shed at the head of the Purple Trail.

Erineum Patches on American Beech leaf lower surface.

Erineum Patches on American Beech leaf upper surface.

One of the ramblers noticed numerous yellow blotches on the upper surface of some of the American Beech leaves. On the underside of the leaf there was an irregular lump beneath each blotch. An abnormal growth on a plant part is called a “gall” and can be produced by the feeding activity of various insects and mites that attack plants. Don discovered that these galls are called “erineum patches” and the culprit is an eriophyid mite. Each patch is produced by the activities of a colony of tiny mites. Visit this website to see what these mites look like.

While we were busy examining the beech leaves another rambler spotted a Jack-in-the-pulpit, the first of several we would see today.The typical "Jack" produces a single leaf that has three leaflets, but many of the plants we see in the Garden have four or five leaflets. To find out more about the sex life of these interesting plants you should visit this page. There is also a lot of variation in the color of the "pulpit," as you can see in these photos:

Jack-in-the-pulpit with a striped pulpit.

Jack-in-the-pulpit with faint green stripes.
Also note there are 4 leaflets on the leaf behind the pulpit.

A cluster of Jack-in-the-pulpit seedlings, all with the typical three leaflets per leaf.
These were probably all from seed produced by a single plant growing in this location.

The typical Jack-in-the-pulpit leaf, with its three leaflets, can be mistake for a trillium. But the trillium leaflets are equally spaced, each leaflet separated by 120 degrees from the adjacent leaflets. In the Jack-in-the-pulpit two of the leaflets are opposite one another and the third leaflet is perpendicular to the other two.

Sap wells even occur on the roots.

Sap wells on the trunk of Hop Hornbeam

Many of the larger Hop Hornbeam trees in the Garden have sap wells excavated by Yellow-bellied Sapsucker woodpeckers. These appear as a horizontal series of holes that look as if they were drilled in the bark. These are excavated by the aforementioned woodpecker and their purpose is twofold: they exude sap that the sapsuckers eat and they also eat insects that are attracted to the sap. The tree soon stops the flow of sap from the wells and this requires the sapsucker to excavate another series of holes. Most trees that have been used by sapsuckers are covered with sap wells from the ground up to as far as you can see.

Muscadine Grape Vine with adventitious roots.

Near the Hop Hornbeam tree there is a large Muscadine Grape vine draped between two trees. The vine has numerous aerial roots descending from its lower side. One is long enough to have reached the ground but is not yet rooted there. What causes the vine to produce these roots is not known, although some have suggested that they are due to damage caused by cold weather.

ID tip: There are two kinds of Grapes to be found in this region: Fox Grape and Muscadine Grape. The vines can be distinguished easily: the Fox vine is covered with “shreddy” bark, whereas the Muscadine vine has tight, smooth bark.

There is a clearing on the Purple Trail that was formed several years ago when a large Northern Red Oak fell. Many of the large fallen trees in the natural areas are of this species. Tall trees are exposed to strong winds and this wind, acting on a tall trunk exerts a large force on the root system. It like an adult and a child playing together on a teeter-totter. A child can counter act the weight of the adult if the child’s side of the teeter-totter is long enough. The taller the tree the greater the force exerted on its root system when the wind blows on the crown. Northern Red Oaks don’t have a strong taproot, so, eventually, they grow tall enough to be pushed over by the wind.

Why twigs fall from trees:

At this time of year we often find the ground littered with twigs, especially under oaks and hickories. A careful examination of the broken ends reveals the reason.

A girdled Northern Red Oak twig. The insect responsible is a Long-horned beetle.

Many of the fallen twigs have been smoothly girdled. Something has carefully removed the outer layer of wood from around the circumference of the twig, leaving it hanging by just the central tissue. The weakened twig will easily fall from the force of rain or wind. It doesn’t take a hurricane to bring them down.

The agent responsible for the girdling is a beetle. The female chooses a twig and lays an egg toward the end. She then walks toward the trunk, stops and starts to chew the outer layer of wood away, circling the twig as she goes. This cuts through the vascular system of the twig which supplies the end with water and that part of the twig dies. When the egg hatches the beetle larva begins to consume the dry, dead wood. Eventually the twig falls to the ground and the larva forms a pupa from which an adult beetle emerges.

Not all twigs that fall are infected with a beetle.

We passed by a little grove of Horse Sugar that we always see when we wander down the Purple Trail. For at lease six years we have never observed these shrubs in flower. They pparently don't get enough sunlight to trigger blooming.

Christmas Fern; the lowest frond will produce spores from the smaller pinnae at the end of the frond.

Christmas Ferns have unfurled their fiddleheads and are beginning to form their fertile fronds. Some fronds show a distinct difference in the size of the pinnae (the “leaves”) in the upper third of the frond. These pinnae are starting to develop structures that produce spores on the undersurface of the upper third of the fronds.

Possum Haw Holly staminate (male) flowers

Linda pointed out a Possum Haw Holly, with flowers.  It differs from the native American Holly and most ornamental hollies in having deciduous leaves. Most of the other native hollies in our area are also deciduous, such as Winterberry and Sand Holly.  Like all hollies, Possum Haw Holly is dioecious, meaning that its female and male flowers are produced on separate plants Dioecy occurs throughout the vascular plant world and is thought to be an extreme solution to the problem of self-pollination. Since the female and male flowers are on separate genetic individuals, there is no chance of self-pollination.

Tuliptree flower; yellow objects are the stamens; the pistils are fused together to form the conical green structure in the center of the flower.

Numerous Tulip Tree flowers could be seen on the ground.  We dissected one to look at the flower structure, including the stamens that surround the central “cone” composed of developing seeds.

Solomon's Plume

Violet Wood Sorrel

Hi Water Trail:

We saw the occasional Blue Eyed Grass, a plant in the Iris family. Like other irises, the leaves are flattened.

An Eastern Tiger Swallowtail flew through the woods.

Kidney-leaved Buttercup and Hooked Buttercup were common along the trail.

Aphids on Cut-leaf Coneflower

Cut-leaf Coneflower is growing at the junction of the Hi Water Trail with the Orange Trail, alongside the creek.  Several of the plants had heavy infestations of red aphids on the stems.

Sensitive Fern; it prefers moist situations.

Orange Trail:

Most of the Mayapples that were flowering two weeks ago are now developing small fruits.

Rue Anemone is now setting fruit; only a few plants were still flowering.
Note the Daddy Longlegs on the leaf to the right.

Violet Wood Sorrel; only a few flowers were blooming in the large patches of purple-centered leaves.

Our big surprise of the day was to find a hundred or more small, dark colored bees swarming back and forth across the stream bank next to the trail. Sometimes as small knot of bees formed on the ground, but mostly they seemed to be patroling the area, rapidly flying back and forth, as if searching for something. 
I don't know what species of bee these are, but I have read accounts of such behavior and I'm confidant I know what is happening here. 
These are solitary bees. "Solitary," here means that the bees are not members of a hive like honeybees. Instead, each female bee digs a tunnel in the soil, provisions it with pollen and nectar and lays an egg on the food mass. The chamber is then sealed and another tunnel dug. (In some cases each tunnel may have more than one chamber.) The female bees do not cooperate with each other even though they may build their tunnels in the same area of suitable soil. It's like an apartment building for single mothers where each child has its own room and the mother only feeds her own child. No one looks after their neighbors kids. The female bees die after a short time, leaving their offspring in the sealed tunnels. By the following spring each larva in its tunnel has become an adult bee. The male bees emerge first and immediately begin searching the area for emerging females. They appear to be able to detect the presence of female bees through odor. As a female digs her way to the surface the males pounce and soon she is surrounded by a group of males, each eager to mate. Those clusters of bees you may have seen are the "mating balls." After mating the males die and the females begin digging tunnels and foraging for food to feed the new generation of bees. 
Don was able to take a video of a mating swarm.

Only a few Wild Geranium are still blooming.

Wild Chervil; note the carrot-like foliage.

Female Dobsonfly

Tom found a female Dobsonfly on the handrail of the bridge. The larval stage, called by fishermen a hellgramite, lives in a fast moving stream for a couple of years before pupating and metamorphosing into the adult stage. The hellgramite is the voracious top predator of the creek. It feeds on all the other invertebrates that live in the stream. The adult Dobsonfly is sexually dimorphic; i.e., males and females look different. The male has an enormous pair of mandibles, but they are so large that he can't really bite with any force. The female, with much smaller mandibles, can give a much more forceful pinch. If you would like to see what the male looks like, just Google "Dobsonfly" and click on any ot the videos that appear in the search results.

Rattlesnake Fern; the fertile frond is in the center, projecting upward and bearing structures that will produce spores.

Broad Beech Fern

 

Crossvine flowers were seen on the ground, setting off a search for the vine. It was finally located near the creek bank, the flowering part high in the trees.

SUMMARY OF OBSERVED SPECIES:

Highbush Blueberry	Vaccinium corymbosum
Gray Squirrel	Sciurus carolinensis
Wood Rush	Luzula echinata
Hickory	Carya sp.
American Beech	Fagus grandifolia
Jack-in-the-Pulpit	Arisaema triphyllum
American Hophornbeam	Ostrya virginiana
Grape	Vitis sp.
Northern Red Oak	Quercus rubra
Girdler Beetle	Oncideres cingulata
Horse Sugar	Symplocos tinctoria
Christmas Fern	Polystuchum acrostichoides
Possum Haw Holly	Ilex decidua
Tulip Tree	Liriodendron tulipifera
Solomon's Plume	Maianthemum racemosum
Violet Wood Sorrel	Oxalis violacea
Blue Eyed Grass	Sisyrinchium sp.
Poa Grass	Poa annua
Eastern Tiger Swallowtail	Papilio glaucus
Kidney-leaf Buttercup	Ranunculus abortivus
Hooked Buttercup	Ranunculus recurvatus
Cut-leaf Coneflower	Rudbeckia lacianata
Sensitive Fern	Onoclea sensibilils
Aphids (red)	Order Hemiptera: Aphididae
Mayapple	Podophyllum peltatum
Rue Anemone	Thalictrum thalictroides
Daddy Longlegs	Order Opiliones
Common Wood Sorrel	Oxalis stricta
Solitary Bees	Order Hymenoptera
Wild Chervil	Anthriscus silvestris
Eastern Dobsonfly	Order Megaloptera, Corydalus cornutus
Rattlesnake Fern	Botrypus virginianus
Broad Beech Fern	Phegopteris hexagonoptera
Crossvine	Bignonia capreolata