Tag Archives: Trees

Winter Tree Identification Part I: Deciduous Trees

In the summer you can recognize the different kinds of trees from the shape and size of their leaves. When trees drop their leaves in the winter months you can use different characteristics such as bud shape, leaf arrangement, bark, and overall growth pattern to identify tree species. As an example, let’s learn how you can identify Red Maple, Green Ash, and Black Walnut. First let’s learn some basic terms!

We will start with leaf or bud arrangement on the stem which will be either “alternate” or “opposite”. The buds are where next year’s leaves will emerge from and the nodes are where the leaf or bud attaches to the stem.

Alternate
Alternate leaf arrangement is when there is one leaf per node.
Opposite
Opposite leaf arrangement is when there are leaves per node (across from one another).

 

 

 

 

 

 

 

 

Leaf Scar
The leaf scar is another important characteristic to look at. This is where the leaf fell off the stem during autumn. Some trees, like the Black Walnut, have very distinctive leaf scars. Their leaf scar resembles a fuzzy smiley face!

Now we area ready to learn some tree species!

GREEN ASH

We will start with Green Ash. First let’s look at the bark and growth pattern:

Ash LS Final

Green ash is typically very straight with a single trunk. The branches usually grow from the top of the tree, not from the sides. The bark is greyish in color with thin furrowed ridges forming an intersecting diamond pattern. Green ash is found growing in lowland areas.

 

 

Now we will look at the characteristics of the twig:Ash LS Notice how the leaf buds are rounded and in an opposite arrangement at the leaf node. The leaf scar is shaped like a half moon or an upside-down “D”. The stem is grey in color and the buds are a dark greyish-brown. There is one bud at the apex, or tip of the stem. White ash is very similar, but the leaf scar has a v-shaped notch on the top and the twigs tend to be gray-green.

RED MAPLE

Red Maple Tree LS Final

Red maples vary in growth pattern. They may grow with a straight trunk or multi branched; like the tree in this picture. Bark is greyish-brown with a thin flaky appearance. Younger trees look smooth, the “plating” or flaky appearance, increases with age. Red maples often grow in swamps but are common in uplands too.

 

Red Maple KS final

Red maples have opposite leaf arrangement. Flower buds usually form high up in the canopy and not on lower branches. Once the flowers have bloomed, leaves will replace them on the same node. The leaf and flower buds are reddish in color, as is the stem itself. The leaf buds are pointed and there is one terminal leaf bud.

BLACK WALNUT

Black Walnut Tree Final

Black walnut trees have a wide branching growth pattern. The bark is dark brown, becoming darker with age. The bark has deeper furrowed ridges than ash, with looser intersecting ridges. Also evident is the dropped compound leaf stalks* underneath the tree. Black walnut trees are found growing in well drained, lowland areas.

*A compound leaf (such as on ash and walnut) has multiple leaflets on the leaf stalk. See below.
Compound leaf

Simple Leaf

Black walnuts have alternate leaf arrangement with a large terminal bud. The buds are fuzzy and light gray in color. The leaf scar is large compared to the bud. The pith (spongy tissue in the center of the stem) is distinctly chambered. This can be seen by carefully taking a sharp blade and cutting the stem in half, as shown in the image below.

Black Walnut LS

Learn more about identifying winter trees in the Winter Tree Identification Part II: Evergreen Trees and Winter Greens blogs.

Post and photos by Lilly Schelling.

 

Emerald Ash Borer and the Polar Vortex

Damage to an Ash trunk by Emerald Ash Borer larvae
Damage to an Ash trunk by Emerald Ash Borer larvae. Photo by NYS Parks

It’s certainly been cold this winter, but current low temperatures, combined with the recent effects of the polar vortex, may deliver unexpected benefits this spring. Foresters and scientists in New York have been fighting against the rapid expansion of the Emerald Ash Borer, an invasive insect which kills ash trees in alarming numbers. The long winter freeze may provide a much-needed advantage against these tiny invaders.

The emerald ash borer is a beetle which arrived in the United States on untreated wood pallets used for shipping from China. In Asia and Russia, the emerald ash borer is kept in check by predators and the natural resistance of ash trees which have had thousands of years to adapt defenses against this parasitic insect. American ash trees, however, have no defenses against this exotic species.

Since they were first identified in Michigan in 2002, emerald ash borers have expanded across the Northern and Eastern United States and killed over 50 million American ash trees. In 2009, these pests were first identified in New York’s Cattaraugus County, posing a new and potentially devastating threat to New York’s forests.

Emerald ash borers kill ash trees by boring underneath the bark into order to lay their eggs. Once hatched, larva feed upon the tree’s living tissue, killing it slowly over the course of 2-3 years.

In wintertime, ash borer larva shelter underneath the bark of ash trees, however, extreme cold temperatures, like we have been experiencing, can freeze the larva even underneath the bark layer and slow down the population growth of this pernicious pest. However, it takes more than just a few hours below zero in the morning to hurt EABs, but sustained sub-zero temperatures could potentially kill a significant portion of the Emerald Ash Borer population. Because EAB larvae shelter deep under the tree’s bark at the base of the trunk and even in the upper roots, where a snow layer can keep them insulated from extreme cold and the tree itself regulates their temperature, they are relatively adept at surviving in cold climates.

For example, this winter at Taughannock State Park near Cayuga Lake, the temperature was never recorded below -8°F (-22°C) and we found Hemlock Wooly Adelgid, another pernicious invasive insect, mortality to be about 88%. On the other hand, at Mine Kill State Park in the northern Catskills, temperatures got to -24°F (-31°C) and we found only about 72% mortality.

For this reason, we can expect the polar vortex to temporarily slow down the expansion of EAB, but management and surveying efforts will continue to be necessary into the future.

Similar:

Invasives and Cold Weather in NY, Cornell University Cooperative Extension.