Ramble Report May 4 2017

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.)

Today's post was written by Dale Hoyt.

Seventeen Ramblers met today.

Announcements:

Saturday, May 13, at 10:00AM:

Natural History of the Scull Shoals Historic Site and the Durham Herb Walk – Geology, Hydrology and Plant Life

A walk guided by our own Don Hunter. You can learn more about the historical significance of Scull Shoals at the Friends of Scull Shoals website. Directions: From Athens drive south to Watkinsville; take GA15 south out of Watkinsville for about 19 miles to Macedonia Rd. Turn left on Macedonia Rd. and travel approximately 2.4 miles to Forest Service Rd 1234 (gravel road) on the left. Turn left onto a gravel road and travel approximately 2 miles to Scull Shoals Historic Site.

Wednesday, May 17, at 5:30PM:

Greenway Expansion Celebration

A free Ice Cream social to celebrate the expansion of the ACC Greenway. Click here for more information.

Today's readings were contributed by Elisabeth and Marguerite. You can read them in the Rambler email with the link to this blog post.

Today's route: Thunderstorms were approaching Athens today and it seemed almost certain that they would hit during the ramble so we confined ourselves to the immediate area of the lower parking lot.

Our focus today was on trees. It's been several months since we paid any attention to trees so I thought it would be a good idea to review basic things about them in the course of learning how to identify some of the common native trees in our area.

Maples

Red Maple leaf

Growing at the lower end of the parking area are a group of Red maples. Their leaves are most commonly divided into 3 lobes but you will occasionally find some with 5 lobes. The edges of each lobe have several teeth (small projections that come to a point). The stalk that attaches the leaf blade to its twig is called a petiole in botany-speak and in Red maple the petiole is frequently red or at least pink in color.

Opposite leaves emerge on opposite sides at the same place on a twig.

Opposite and alternate leaves

The leaves in Red maples (and other kinds of maples) are attached to their twigs opposite one another. Of the trees we found today only the Maples and Buckeye have opposite leaves. The others all have alternate leaves – their leaves do not emerge from the twig in pairs opposite to one another. Instead, adjacent leaves are separated by some distance.

The opposite or alternate arrangement of leaves is very useful in identifying trees because it eliminates a lot of possibilities. If your tree has opposite leaves then it is most likely a maple, buckeye, dogwood or ash. There are a few other possibilities, but they are far less common here. There are more tree species with alternate leaves in our area.

Florida maple upperside of leaves is darker than undeside.

Florida maple underside of leaves is lighter

Chalk maple; lobes are broader at base, tapering toward tip.
(Compare to Florida maple: narrower at base, wider at tip.)

Nearby the Red maples are three other kinds of maple: Florida maple, Chalk maple and Sugar maple. The Sugar maple is not native to this area. Florida maple is considered by some botanists to be merely a variety of Sugar maple, but others think that the differences are sufficient to give it recognition as a distinct species. All three of these maples have leaves that look like the one on the Canada flag: they have five lobes and the lobes have smooth edges, lacking the teeth found on the Red maple. The middle lobe of the Chalk and Florida maple differ from one another in shape. The base of the lobe is wider than the tip in the Chalk maple and narrower in the Florida maple. The underside of the Florida maple is whiter than the upperside, whereas the underside of the Chalk maple is a paler green than the upperside. Chalk maple also has a fuzzier underside than the Florida maple.

Chalk maple gets its common name from the light color of the bark. It also tends to produce multiple trunks as it grows and is a generally smaller tree.

A question was asked about the maples seen in many yards in town. These are Silver maples, which are not native to this area, but are often planted in suburban neighborhoods because they grow rapidly. They do show strikingly different color above (dark green) and below (silvery white), especially evident when a breeze blows them about.

The Sugar maple by the sidewalk has a very dark trunk that is not typical of the species. It is caused by a mold growing on sap that runs down the trunk. The sap comes from small holes made by sapsucker woodpeckers. The woodpeckers tap shallow holes in the bark of trees, causing sap to leak. This leakage attracts insects and the sapsuckers happily feed on the bugs as well as the sap. The mold that grows on the excess sap is similar to the discoloration you see on roofs and cement driveways where they are below tree branches. In those cases the sugar comes from aphids or other sap-sucking insects that excrete "honeydew," the sugary fluid that splatters your windshield when you park beneath a tree.

What is a leaf? This seems like a simple question with an obvious answer: a flat, green thing on a plant. But, as they say, the devil is in the details. A leaf could also be defined as the thing that falls off a tree in autumn. It might surprise you to learn that these two definitions don't identify the same thing. This was exemplified today by the Mockernut hickory leaf. This large leaf is composed of nine leaflets. It is called a compound leaf, a leaf composed of more than one leaflet. The leaves of the maples we saw are all simple leaves. The problem many people have when they are learning about leaves is how to distinguish between a leaflet and a leaf. If you look at where a leaf is attached to a twig you will find a bud. This bud will produce another leaf in the following year. So, if you follow what you think might be a leaf back to its attachment point and you don't find a bud, you have a leaflet. This will seem difficult at first, but with a little practice you'll soon be identifying leaves and leaflets.

Mockernut hickory pinnately compound leaf
Each "leaf" is a leaflet; leaf has 9 leaflets

Red buckeye palmately compound leaf
Each leaf has 5 leaflets

Compound leaves come in two varieties: pinnate and palmate. Mockernut hickory is a good example of a pinnately compound leaf. The palmately compound leaf we saw was the Red buckeye. To describe the difference between them it's useful to introduce some more terms. With a simple leaf the petiole is the part of the leaf that attaches the leaf blade to the twig. In a compound leaf there is new part, the rachis. This is the part of the leaf to which the leaflets are attached. So, using this terminology, the palmately compound Buckeye leaf has no rachis – all it's leaflets attach to the petiole, like all your digits attach to your palm. In the pinnately compound hickory all the leaflets are attached to the rachis. (In most cases all the leaflets will be attached to the rachis in opposite pairs, except the terminal leaflet, which is attached to the end of the rachis.

Ailanthus; large pinnately compound leaf with many leaflets

Another tree we saw today, Ailanthus or Tree of Heaven, has really long compound leaves with lots of leaflets. It is a native of Asia and was introduced into the United States early in the 19th century. It soon spread and almost literally will grow anywhere, which makes widespread in urban settings. It does seem to prefer cooler, more northern areas. In addition to the long, compound leaves it has an unpleasant odor that many people fine offensive.

Oaks

Oaks in our area are divided into two groups: White oaks and Red oaks. The confusing thing is that there are two oak species called White oak, and Red oak, that belong to the White oak group and the Red oak group, respectively. The difficulty lies in confusing when someone is talking about the group or just the individual species. Be on guard and if you are uncertain always ask if someone is talking about the group or the species. There are many significant differences between these two groups, but today we're just focusing on identification of the leaves. More on the other differences in a later post.

White oak; simple leaf with rounded lobes

Post oak; simple leaf with rounded lobes;
large lateral lobes at 90 degree angle make a cross shape.

White oaks (the group, not just the White oak) have simple, alternate leaves that are divided into rounded lobes. The lobes lack sharp points (sometimes called "prickles").

We saw two kinds of White oaks today: White oak (Quercus alba) and Post oak (Quercus stellata). Post oak has a very distinctive leaf shape: two large lateral lobes project at an approximately 90 degree angle from the central axis of the leaf, giving the leaf a cross-shaped appearence.

Red oaks (the group, not just the Red oak) have simple, alternate leaves that are divided into pointed lobes. The lobes come to a sharp point that extends beyond the leaf blade.

Northern Red oak; simple leaf with pointed lobes

We saw one kind of Red oak today: Northern Red oak (sometimes confusingly just called Red oak.)

The remaining trees we identified today all have alternate, simple leaves and can be identified by details like shape of the leaf blade and presence or absence of teeth on the leaf margin, as well as some non-leafy features.

Black gum; simple leaf with smooth margin

Black gum branches arise at 90 degree angle to trunk

Black Gum has oval leaves with a smooth margin, except for a presence of small protrusions on some leaves. The end of the leaf is often pointed. One of the best ways to identify this tree is the branching pattern. The branches emerge at right angles to the trunk. In most trees the branches angle upward.

Winged elm; simple, almond-shaped leaves with toothed margin

Winged Elm has almond shaped leaves with a toothed margin. Some branches have corky ridges, called wings, that run lengthwise, but these are often absent. Another tree we didn't look at today that has similar wings is Sweet gum.

Redbud; simple, heart-shaped leaves with smooth margin

Redbud has leaves shaped like a broad, fat heart with smooth margins. It frequently has bean pods on its branches, because it's a legume, like peas and beans.

Black cherry; simple leaves with finely toothed margin

Black Cherry also has almond shaped leaves but the margin is very finely toothed, not as coarse as Winged elm. The trunk of cherry trees has horizontal slits, called lenticels, that let air into the tissues under the bark. They are obvious on young trees, but as the tree gets older the bark becomes thicker and it is harder to see lenticels. Finally the bark resembles crushed, burned potato chips.

Northern red oak shade adapted leaves

Sun leaves vs. shade leaves

We found Northern Red oak leaves on saplings growing in the shade and also some leaves from the upper part of a tree, where they had been exposed to winds and full sunlight. These "sun" leaves and "shade" leaves look so different you might think they were from different species. They are adapted to the different environments they grow in. A shade leaf is thin and broad, whereas a sun leaf is thicker and narrower. They differ in color as well – a sun leaf is much darker green and a shade leaf much lighter. The difference in color is a consequence of how much chlorophyll each leaf has per square inch. The sun leaf has more chlorophyll per square inch because it has more chlorophyll bearing cell layers, making it greener and thicker. So why doesn't the shade leaf have more chlorophyll? Chlorophyll costs a lot of energy to make. If a leaf is growing in the shade there is not a lot of light energy to harvest. If the shade leaf added another layer of chlorophyll bearing cells they would not be very efficient because they would be shaded out by the cells above them. This would make the lower cell layer energy inefficient – it would cost more energy to make the chlorophyll than the chlorophyll could capture from the dim light in the shade.

In full sun the leaf has a different problem. The heat of the sun combined with the wind makes it easy to lose water. The shade leaf is out of direct sunlight and the winds are not as extreme is its sheltered location. It can afford to have a large surface area because it won't lose water as fast as the sun leaf. By being smaller the sun leaf conserves water.

How trees grow

New growth is green; last years twig is brown

Growth from the tips of branches.

The growth in length occur at the tip of a branch. Each year there is a flush of new growth as a terminal bud opens and the new shoot with its already formed buds and leaves lengthens. But the year old growth, from which the new shoots emerges, does not change in length. Neither does the two year old growth. You can see this clearly at this time of year because the new shoots are usually still green in color and easily distinguished from the older part of the branch.

The terminal bud is usually protected by bud scales that enclose it. When spring arrives the bud swells and the scales fall off as the new shoot emerges and lengthens. The place where the scales were attached appears as scarred ring around the twig. You can work backward from the new growth to the previous year's bud scar to see how much the branch or twig grew last year. Sometimes you can follow the scarring back several more years, but it gets harder as the scars become faded due the growth of the twig or branch in circumference.

Growth in circumference. All the branches of a tree, including the main branch we call the trunk, are surrounded by a thin layer of cells called the cambium. If you scratch through the bark of a young branch you will see a bright green surface just under the bark. This is the cambium and it is responsible for the growth in diameter of the trunk, branch and twig. Focus now on the cylinder of cambium cells that surround a tree trunk. When they divide they produce new cells either on the inside or the outside or on the right or left of the parent cell, but not above or below. Cells added to the inside push the parent cells away from the center of the trunk. Cells added to the right or left increase the circumference of the cambium layer. But because the division is only either forward, back or to the side, the original cell doesn't get any higher. This is why, if you drive a nail into a tree trunk four feet from the ground, after 20 years of growth that nail will still be four feet from the ground. (But the tree might have grown around the nail in that time.)

This pattern of growth causes an increase in diameter and puts the bark of the tree under stress, like your belt when you gain weight. The bark has its own layer of cambium cells, called the cork cambium. When they divide the bark gets thicker and if they divide rapidly enough they can compensate for the increased circumference of the tree they cover. It's like having a belt that continually lengthens to match your waistline. The smooth, gray bark of a Beech tree is a good example. The cork cambium of the Beech keeps pace with the growth of the trunk so the bark always covers it with no splitting or gaps. In most other trees the bark can't keep pace with the underlying growth and it begins to crack and split, creating the blocks and ridges that we see in most tree trunks.

But what happens to the cells that end up inside the cylinder of cambium? They become part of the trees vascular system. They develop into long tubes called xylem that carry water and dissolved mineral nutrients from the roots to the leaves. Collectively, this xylem is called sapwood. A new layer of sapwood is added each year. As the tree grows a ring of sapwood is added each year, thicker in good years and thinner in bad years. Eventually the cells of the wood in the center of the tree die and their remains become impregnated with rot-resistant material that makes them a different color. They are collectively called heartwood.

Extent of new growth

Fun homework!

Find an accessible branch of a tree in your yard or neighborhood. Measure the length of the new growth at the end of the branch. Count the number of leaves on the new growth. Record your observations and the date. Mark this branch so you can find it again. Revisit the branch every week or two during the summer and make the same counts and measurements. Note any other changes you see. Keep records for each date. At the end of the summer bring your data to a Ramble to share with others.

Other things to do at home: Check the new growth on your trees. Is the amount of growth the same in all the branches? Is it different on the north, south, east or west side of the tree? Do different kinds of trees differ in the extent of new growth? At the base of this year's new growth there is a scar from last year's terminal bud scales. If you follow last year's twig back you can find a similar scar that represents when last year's twig was new growth. How does the amount of growth compare between this year and the previous year?

Poison ivy vine with hairy rootlets

Poison ivy vine; each leaf with 3 leaflets

Poison Ivy, urushiol, Poison Oak

Poison Ivy is a vine with many hairy rootlets that cling to trees, enabling the vine to climb upward where there will be more sunlight. Each leaf has three leaflets, the basis for the saying: "Leaflets three, let it be." It grows profusely everywhere in the Garden, so it's a good idea to learn how to identify it. That's the best way of avoiding it.

The itchy, sometimes painful pusutles are caused by an oily compound called urushiol, that appears when poison ivy leaves are damaged. The pustules are produced by the reaction of your immune systems to the urushiol. Sensitivity is either innate or is acquired by repeated exposure. If you've been exposed to poison ivy the best thing you can do is to wash the affected area with a strong soap or detergent as soon as you can. The oily urushiol will be carried away by the soap, contrary to what some internet sites say. Water alone will not work. Without soap or detergent you run the risk of spreading the oil to more places.

Poison oak is a plant similar to poison ivy that is now recognized as a different species (it was thought previously to be a variety of poison ivy). It grows as a small shrub, rather than a vine, but still has three leaflets per leaf. The leaflets are often lobed, which makes them resemble some species of oak, the basis for its common name. It also produces urushiol. In Georgia I have seen Poison oak in the coastal plain, but never in the mountains or piedmont. Poison oak is found in the far west whereas poison ivy is primarily found in the midwest and east.

Insects

Eastern tent caterpillar nest in Black cherry

We spotted an Eastern Tent caterpillar nest at the juncture of several branches in the Black Cherry tree. The nest is made of silk produced by the caterpillars that live in it. A mass of eggs is laid on the tree in the spring by the female moth. This egg mass overwinters and hatches the following spring. The hundred or so nest mates begin to construct the web at a point where two or more branches emerge. They also feed on the leaves at the end of the branches, traveling out of the nest to feed and then returning to the nest to produce more silk and increase its size. They periodically molt inside the nest and when they become full grown, leave the nest and wander about, looking for a place to form a cocoon. The adults emerge, mate and the female lays her mass of eggs on another cherry tree.

The nest offers protection against predators. It is tough and hard to penetrate. I once watched a paper wasp, an eager eater of caterpillars, spend 10 minutes trying to get inside a tent caterpillar nest and failing.

These nest are usually seen only in the spring and mostly found in cherry or related trees (apples, pears).

Fall webworm caterpillars inside nest

Fall webworm nests at end of branches in Redbud

Another moth with caterpillars that make silken nests is the Fall webworm and one of the Ramblers spotted a nest at the end of a Redbud branch. Unlike the Tent caterpillar the Fall webworm encloses the end of a branch in silk and eats the leaves in the safety of its nest. As the caterpillars grow they increase the size of the nest until sometimes two or more branches are completely enclosed.

As the common name indicates you usually only see these nests on trees toward the end of summer. This is the earliest I've seen one in Athens. Fall webworms are not as picky about the trees they eat. You can find them on a large variety of different species, unlike the Eastern tent caterpillar, which prefers cherry.

Asian multicolored lady beetle larva

Asian multicolored lady beetle pupa

Asian multicolored lady beetle adult

Asian multicolored lady beetle adult

Asian multicolored lady beetles
showing extreme color variation
entomart Wikimedia commons

Ladybugs are becoming more abundant and today we saw three different stages in their life cycle: larva, pupa and adult. They are not bugs, they are beetles, so the proper name for them should be Ladybeetle, but insisting on that is swimming upstream. All the stages we found are of one species, the Asian multicolored lady beetle. This species was introduced to control scale insects in citrus orchards and did a great job. The only problem is that it out competes our native lady beetles. Since the AMLB arrived more and more of our native species have begun to disappear. All lady beetles eat the eggs of other lady beetles when they discover them. But the AMLB coats its eggs with a chemical that kills our lady bugs when they eat them.

The AMLB gets its name from the extreme variability in color and pattern as seen these photos. Identifying the AMLB is best done by looking for a black letter M behind the eyes. It is surrounded by white. This is not 100% accurate, but nothing else works as well.

SUMMARY OF OBSERVED SPECIES:

Red maple	Acer rubrum
Florida maple	Acer floridanum
Chalk maple	Acer leucoderme
Sugar maple	Acer saccharum
Mockernut hickory	Carya tomentosa
Red buckeye	Aesculus pavia
Bordered Plant Bug	Largus succinctus
White oak	Quercus alba
Post oak	Quercus stellata
Black gum	Nyssa sylvatica
Mulitcolored Asian ladybug (larva, pupa and adult)	Harmonia axyridis
Winged elm	Ulmus alata
Northern red oak	Quercus rubra
Tree of Heaven	Ailanthus altissima
Poison ivy	Toxicodendron radicans
Virginia creeper	Parthenocissus quinquefolia
Eastern redbud	Cercis canadensis
Black cherry	Prunus serotina
Eastern tent caterpillar	Malacosoma americanum
American wisteria	Wisteria frutescens “Alba"
Fifteen-spotted ladybug	Anatis labiculata
Fall webworm caterpillars	Hyphantria cunea
Persimmon tree	Diospyros virginiana
American hophornbeam	Ostrya virginiana
Green ash	Fraxinus pennsylvanica
Orange-patched Smoky Moth	Pyromorpha dimidiata
Thimbleweed	Anemone virginiana