Winter Tree I.D. : A Few Easy Examples

Winter identification of trees usually includes examining the bark, twigs and buds, and sometimes the general form of the tree in question.  Branching patterns are seldom used for identification, and are often either non-specific or common to a number of different trees.  The Black Gum (Nyssa sylvatica) is an exception, with its unique horizontal branching easily seen from the ground.  The upper branches and twigs come off the main branches at right angles, creating an antenna-like form that is striking in its regularity.  See the two examples below.

Nyssa sylvatica
Black Gum
Branching Pattern

Nyssa sylvatica
Black Gum
Branching Pattern

For contrast, the branches of a Willow Oak (Quercus phellos) are shown below.  Typical of most oaks, the branches reach upward and are often curved, with few if any right angles to be seen.

Quercus phellos
Willow Oak
Branching Pattern

Not totally unique but distinctive is the bud and twig patterns of the Slippery Elm (Ulmus rubra).  The twigs, with their large, red buds, form a zig zag pattern that appears almost electrified when viewed from below.

Ulmus rubra
Slippery Elm
Branches and Twigs

The Box Elder (Acer negundo) is another tree that is usually easy to identify in winter.   As Box Elders mature, they produce a copious number of branches and shoots.  Even older trees produce clusters of shoots, sometimes directly from the trunk.  These shoots are smooth and are a distinctive green color, which causes them to stand out against the browns and grays of winter.  The new branches of a young tree are pictured below.

Acer negundo
Box Elder
Green Twigs and Shoots

Below is an older, mature Box Elder with clusters of new green shoots coming out in several places along the main trunk of the tree.

Acer negundo
Box Elder
Green Shoots

The Sweet Gum, Liquidambar styraciflua, is both common and abundant in Central North Carolina.  And it is very easy to identify in winter due to the high numbers of new, yellow-brown branches and twigs displayed by young, growing trees.  Below is a group of young Sweet Gums.  In the second photo, the large buds stand out even at a distance.

Liquidambar styraciflua
Sweet Gum
Twigs

Liquidambar styraciflua
Sweet Gum
Twigs

As Sweet Gums age, and developing bark begins to cover most of the branches, the distinctive large, terminal buds remain conspicuous.  They are colorful and shiny, almost as if they had been waxed.  And the overlapping bud scales are easy to see.  They display a large range of colors that are often not mentioned in the bud identification guides.  The yellow-brown bud below is the most common.

Liquidambar styraciflua
Sweet Gum
Yellow-brown Bud

Shiny, reddish buds are seen occasionally.

Liquidambar styraciflua
Sweet Gum
Reddish Bud

And buds with a green tint are also seen.

Liquidambar styraciflua
Sweet Gum
Green-brown Bud

Oaks have alternate buds that occur in clusters at the tip of the twig.  Bud scales are obvious and the bud color is usually a shade of brown or red.  Determining the exact species of oak using the bud and twig can be done, but is somewhat of a specialty.  Many twig and bud identification keys simply end with “Oak” or “Quercus sp.” and don’t try to go any further.  Below is the twig and bud from a Southern Red Oak (Quercus falcata).

Quercus falcata
Southern Red Oak
Twig and Buds

There are many on-line winter twig and bud identification keys.  Here is a good one by Jon Stucky of North Carolina State University:

https://projects.ncsu.edu/cals/plantbiology/ncsc/TwigID/

Herb Amyx

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Searching for the Elusive “Slippery” Elm – Ulmus rubra

Slippery Elm (Ulmus rubra) is a common native tree in North Carolina, with most populations found in the Piedmont and Mountain regions.  Surprisingly, Slippery Elms do not appear on the plant lists from many of our major state parks.  This includes the Jordan Lake and Kerr Lake State Recreation Areas, which have thousands of forested acres in the very heart of Slippery Elm territory.  There are several possible explanations for this disparity.

Along with American Elm (Ulmus americana), Slippery Elm populations were devastated by Dutch Elm Disease starting in the  1930s and continuing even today.  As a result, Slippery Elm has a patchy distribution, often occurring as solitary  individuals and almost never in single species stands.  Thus the isolated nature of their occurrence makes them easier to overlook.

Another important factor is the difficulty distinguishing Slippery Elm from American Elm.  They are physically very similar and both live in similar bottomland habitats.  Therefore  it is very possible that Slippery Elms are mistaken for, and  recorded as, the more familiar American Elm.  It follows then that the most important factor in identifying Slippery Elm is to understand the field signs that distinguish  it from American Elm.

Differences in the leaves are a major factor in telling the two species apart.  The leaves of both species are large, have strongly serrated margins, are double-toothed, and have asymmetrical bases.  But the leaf tips of Slippery Elm have an extended tip that arises suddenly and abruptly  from the leaf margins, as seen in the two photos below.  While American Elm has an extended tip, it arises smoothly and evenly from the leaf margins.

Ulmus rubra
Slippery Elm
Leaves

The photos above and below also illustrate another important field sign.  The leaf blades of Slippery Elm often rise upward from the central leaf vein, giving the leaf a partially folded appearance.  The leaves of American Elm appear flat.

Ulmus rubra
Slippery Elm
Leaves

The fall and winter buds of Slippery Elm are distinctive in their reddish color, which often stands out brightly in the winter sun.  The red buds are the inspiration for the scientific species name “rubra”.  The two following photos were taken at the end of last November.

Ulmus rubra
Slippery Elm
Fall Buds

Ulmus rubra
Slippery Elm
Fall Buds

The photo below was taken in early January.  The reddish color of the buds varies.  The bud seen below has scales that are very dark , almost purplish red.  The buds  are also frequently a rusty color, and can be hairy.

Ulmus rubra
Slippery Elm
Winter Buds

Slippery Elm winter twigs (seen below) have a heavy, gray, fuzzy pubescence that is most pronounced at the terminal end of the twig.  American Elm has smooth twigs.  While this is a dramatic contrast between the two species, a drawback is that it requires magnification to be seen clearly, and varies in intensity from one twig to another.

Ulmus rubra
Slippery Elm
Hairy Twigs

The bark of Slippery Elm is too variable to be of much help with field identification.  The trunk shown below has a grayish color with long vertical ridges and some weaving.  Other trunks are dark brown and have intermittent or obscure ridging and weaving.

Ulmus rubra
Slippery Elm
Trunk and Bark

And finally, the small, round American Elm seeds (called samaras) have a distinct notch at the top, while Slippery Elm seeds have no notch at all.  This can be a helpful field sign, but the seeds are limited to a brief period in the spring.  The seeds are highly valued by birds, who feast on them while still on the tree, and clean them up  quickly when they hit the ground.

In summary, a condensed recipe for distinguishing Slippery Elm is:

In spring and summer, watch for the folded leaf with the sudden and abrupt extended leaf tip.  In fall and winter, look for the red buds.  When in doubt, look for pubescent twigs and seeds with no notch at the tip. 

Herb Amyx

 

Fall Leaf Patterns: Swamp Chestnut Oak, Shumard Oak, and Scarlet Oak

Fall is a delightful and convenient time to study tree leaves.  What was once 80 feet overhead and practically invisible, is now directly underfoot and at hand.  The Neuse River Trail, running beside the Neuse River south of the Falls Lake Dam, is home to many spectacular bottomland tree species.  Huge Swamp Chestnut Oaks (Quercus michauxii) and Shumard Oaks (Quercus shumardii) can be found here, and their branches produce thousands of fall leaves that carpet the asphalt greenway.

Swamp Chestnut Oaks are common in the North Carolina Piedmont and Coastal Plain bottomlands.  Their leaves have wavy edges with short, rounded lobes, and are distinctive in this habitat.  Chestnut Oak (Quercus montana), which has similar leaves, is not found in this wet environment, but is an upland species.  In addition, Swamp Chestnut Oak leaves are widest toward the end of the blade, well past the middle, while Chestnut Oak leaves are widest in the middle.  Below are Swamp Chestnut Oak leaves that illustrate the normal variability in size and shape that is commonly seen.

Quercus michauxii
Swamp Chestnut Oak
Leaves

The bark and trunk of a mature Swamp Chestnut Oak is chalky and pale, with scales that loosen with age.  It is similar to and is sometimes mistaken for White Oak (Quercus alba).

Quercus michauxii
Swamp Chestnut Oak
Bark

Quercus michauxii
Swamp Chestnut Oak
Trunk

The Shumard Oak (Quercus shumardii) is uncommon in North Carolina, but can be found in sporadic populations along the Neuse River Trail.  They are very tall trees, and in some cases stand directly adjacent to Swamp Chestnut Oaks.  The leaves are broad and deeply cut, with many lobes and large numbers of bristles at the tips of the lobes.  They present a highly dissected, intricate pattern.  Several leaves below on the far left have nine lobes.

Quercus shumardii
Shumard Oak
Leaves

The trunk of the Shumard Oak is tall and straight, and has dark furrows highlighted by light ridges that run vertically up the trunk.  It often resembles the trunk of the Northern Red Oak (Quercus rubra).   The gray, vertical ridges can be shiny and are sometimes referred to as “ski tracks”.

Quercus shumardii
Shumard Oak
Trunk

Scarlet Oak (Quercus coccinea) is found in a very different habitat than Swamp Chestnut Oak and Shumard Oak, preferring upland forests and dry, rocky soils.  Scarlet Oak leaves bear a close resemblance to Shumard Oak leaves.   The differences can be subtle.  Scarlet Oak leaves are also deeply cut but the sinuses are wide open, while the Shumard Oak sinuses tend to narrow or close, causing the sinus to have a tear-drop shape.  Scarlet Oak leaves tend to be proportionately narrower than Shumard Oak  leaves.  Nine lobes are commonly found in Shumard Oak, while they are rare in Scarlet Oaks.  See the Scarlet Oak leaves below.

Quercus coccinea
Scarlet Oak
Leaves

Scarlet Oak trunks have gray, low, irregular ridges, with deep furrows seen in older trees.

Quercus coccinea
Scarlet Oak
Base of Trunk

Quercus coccinea
Scarlet Oak
Trunk

Will Cook has an important observation about Shumard Oak leaves in his Carolina Nature website: Trees, Shrubs and Woody Vines of North Carolina.  “The leaf undersides show a distinctive feature of Shumard Oak: tan tufts of hairs in the axils of the veins. Related oaks may have tufts of hairs in the veins, but they tend not to be as pale tan or as tufted.”  The tufts of hair in related oaks also do not survive the seasons of wind and rain like those in Shumard Oaks.  The first two photographs below illustrate the remnant hairs in the vein axils of Shumard Oak leaves.  The third and final photograph is of the underside of a Scarlet Oak leaf, typical of many that were examined.  It shows no visible remaining tufts of hair in the leaf vein axils.  Although no single feature is absolute in fall leaf  identification, this one is excellent.

Quercus shumardii
Shumard Oak
Tufts in Leaf Axils

Quercus shumardii
Shumard Oak
Tufts in Leaf Axils

 

Quercus coccinea
Scarlet Oak
Bare Leaf Axils

Many variables interact to affect leaf patterns and shapes.  Most of the leaves in the above photographs were sun leaves, meaning they came from the upper crown of the tree where they get the most sun.  Those from the shaded base of the tree tend to have shorter lobes and smaller sinuses and often are not as intricate and graceful.  Leaf shape is important but is almost never used alone to confirm the identity of a tree.

Herb Amyx

 

 

 

The Southern Grape Fern (Sceptridium biternatum) in North Carolina

Southern Grape Ferns (Sceptridium biternatum) are common in moist forests throughout the Piedmont of North Carolina.  They are small ferns, usually 3 to 6 inches across, and have a fleshy, succulent texture.  They are members of the Adder’s Tongue family (the Ophioglossaceae), which is sometimes referred to as a family of succulent ferns.  Until fairly recently, they were classified as Botrychium biternatum, and the new genus name of Sceptridium has been slow to be recognized.

Southern Grape Ferns emerge in the summer and early fall, and remain throughout the winter.  Pictured below is the typical form most frequently seen on the forest floor.

Sceptridium biternatum
Southern Grape Fern

They often appear in small clusters, as illustrated below.

Sceptridium biternatum
Southern Grape Fern

Southern Grape Ferns are variable in color, shape and size.   An individual with a yellow tinge is shown below.

Sceptridium biternatum
Southern Grape Fern
Color Variation

In the fall, fertile fronds arise from the base.  A frond  is the leaf of a fern, and a fertile frond is a highly specialized frond that differs markedly in form and size, and carries the sporangia.  The sporangia are the cases or capsules that bear the spores of the fern.

Sceptridium biternatum
Southern Grape Fern
Fern and Fertile Frond

Below is a closer look at a fertile frond bearing sporangia.  The shape of the fertile frond is said to resemble a king’s scepter, which gave rise to the genus name Sceptridium.

Sceptridium biternatum
Southern Grape Fern
Fertile Frond

Below is a closer look at the golden sporangia.  Their resemblance to clusters of grapes is the source of the common name Grape Fern.

Sceptridium biternatum
Southern Grape Fern
Sporangia

Sceptridium dissectum – the Cut-leaf Grape Fern – is a close relative of the Southern Grape Fern, and is rare in Central North Carolina.  It was also classified as a Botrychium until recently and was considered a form of the Southern Grape Fern.  It has now  been moved into its own separate genus and species.  The fronds of this species are divided for a third time, creating a fragile, lace-like appearance, making it easily distinguishable from the Southern Grape Fern, whose fronds are twice divided.

Sceptridium dissectum
Cut-leaf Grape Fern

Sceptridium dissectum
Cut-leaf Grape Fern

There are two forms of the Cut-leaf Grape Fern; one of them complicates field identification.  Forma dissectum is the rare one illustrated by the two photos above.  It is easily identified.  Forma obliquum (not illustrated) is much more common and can closely resemble the Southern Grape Fern, leading to confusion.  Perhaps the best way to be certain of identity is to look closely at the margins of the frond.  The two close ups below show the sharply serrated margins of the fronds of Southern Grape Ferns.  These serrations can be seen in the field without magnification.

Sceptridium biternatum
Southern Grape Fern
Serrated Margins

Sceptridium biternatum
Southern Grape Fern
Serrated Margins

The frond margins of both forms of the Cut-leaf Grape Fern are usually  completely smooth or at most have indistinct or obscure serrations.  The close up below shows the divisions of the frond, looking like jigsaw pieces, but the  complex margins can be seen as completely smooth without serrations.

Sceptridium dissectum
Cut-leaf Grape Fern
Entire Margins

The Southern Grape Fern (Sceptridium biternatum) can also be confused with the Rattlesnake Fern (Botrypus virginianum) which has a very similar form and appearance.  There is a simple way to distinguish them.

The Rattlesnake Fern is deciduous and the Southern Grape Fern is evergreen.  The Rattlesnake Fern arises in the spring and is gone by late summer and fall.   The Southern Grape Fern arises in the summer and fall, and remains throughout the winter.

Herb Amyx

 

 

 

North Carolina’s Yellow Giant Hyssop – Agastache nepetoides

Yellow Giant Hyssop (Agastache nepetoides) is a rare plant in North Carolina, found almost entirely in the Central Piedmont and confined to only a few counties.  North Carolina is on the perimeter of its natural range, which is primarily the Midwest and Mid Atlantic.  It is rated by the N.C. Natural Heritage Program as status: Significantly Rare-Peripheral, and rank: Critically Imperiled.  It is a tall (up to 7 feet), rangy native perennial, and a member of the mint family, the Lamiaceae.  The population discussed below is located in a wooded area over mafic rock, with light shade and a small period of full sun.

As seen below, the mature plants tend to mass closely together to form a loose thicket.

Agastache nepetoides
Yellow Giant Hyssop
Mature Plants

The stems are square with a small, winged ridge running up each corner.  They are strong,  wind resistant, and tend to persist over the winter after all the foliage is gone.

Agastache nepetoides
Yellow Giant Hyssop
Square Stem

The leaves of mature plants are opposite, coarsely serrated, deeply textured, and are usually  broadly lanceolate (shaped like an arrowhead).

Agastache nepetoides
Yellow Giant Hyssop
Leaf

Below is a group of smaller plants separated from the main thicket, allowing a little better look at the plant form.  The main stems are tall and slender, with only a few branches.

Agastache nepetoides
Yellow Giant Hyssop
Plant Form

In North Carolina, Yellow Giant Hyssops begin new growth at the base of last year’s stem.  The photo below was taken in mid February by lightly brushing  the leaf litter away from the base of the stem.

Agastache nepetoides
Yellow Giant Hyssop
Emerging Plants in Spring

By the first of April, growth of the new plant is well underway.

Agastache nepetoides
Yellow Giant Hyssop
Spring Plant Growth

Most of the leaves seen in April are shorter and broader than the leaves seen in the mature plant.

Agastache nepetoides
Yellow Giant Hyssop
Young Leaf

By mid April, plants are showing significant growth.  Notice in the first photograph below, there are three separate plants, each arising from the base of a dead stem.  In the second photograph, there is one plant arising from one dead stem.

Agastache nepetoides
Yellow Giant Hyssop
Spring Plant Form

Agastache nepetoides
Yellow Giant Hyssop
Spring Plant Form

In the spring, what was the terminal flower spike is now dried seed capsules.  By late April, most of the seeds have been dispersed and the capsules are empty.

Agastache nepetoides
Yellow Giant Hyssop
Seed Capsules

In the large clusters of Yellow Giant Hyssops, there are also seedlings coming up in the early summer from spring seed germination.  This population produced large numbers of seedlings scattered about the periphery.  The leaves are softer and thinner than those from perennial plants.

Agastache nepetoides
Yellow Giant Hyssop
Seedlings

Some of the seedlings become quite tall by mid summer and go on to bloom when they reach three to four feet in height.

Agastache nepetoides
Yellow Giant Hyssop
Seedling

The area where the seedlings above were growing was heavily browsed by deer.  Below is a photo of Clammy Ground Cherries (Physalis heterophylla) showing the obvious deer predation.   These Ground Cherries were scattered about with the seedling Yellow Giant Hyssops, which were completely untouched by the deer.    Agastache sp. in general have a reputation for being shunned by deer.  This is one of those rare times when field observations actually confirm the deer resistant reputation.

Physalis heterophylla
Clammy Ground Cherry
Browsed

The terminal spikes of the Yellow Giant are dense with flowers, but generally only a few bloom at a time, giving the look of a bare and uneven bloom. But in this population, illustrated below, there were a number of individuals that had showy blooms.  The flowers are tubular with the lower lip being longer than the upper.  In the closer view provided by the second photo, the flower structure and especially the long, extended stamens (the male reproductive organ) can be seen.

Agastache nepetoides
Yellow Giant Hyssop
Flowers

Agastache nepetoides
Yellow Giant Hyssop
Flowers

As mentioned in the introduction, Agastache nepetoides – Yellow Giant Hyssup – is a critically imperiled species in North Carolina.  This means that it occurs in only five or fewer locations within the state, or there are very few remaining individuals, i.e. less than one thousand.  Fortunately, there are at least two sites in the Central Piedmont where small populations are being protected and managed, with the hope of eventually expanding the number of individuals and populations.

Herb Amyx

 

Infested Southern Hackberries (Celtis laevigata) in a Suburban Park

The Southern Hackberry (Celtis laevigata) is a common tree in the Piedmont of North Carolina, often occurring along rivers and streams, and in suburban parks.  In one large park near Falls Lake, and in the surrounding forests nearby, many Southern Hackberries are visibly discolored and ragged looking, as if someone had tossed a bucket of soot or ash over the foliage of the tree.  The two trees pictured below illustrate this appearance.

Celtis laevigata
Southern Hackberry
Tree With Sooty Mold

Celtis laevigata
Southern Hackberry
Tree with Sooty Mold

Closer examination of the foliage shows most of the leaves covered with a sooty mold.

Celtis laevigata
Southern Hackberry
Leaves with Sooty Mold

Examination of the undersides of the leaves reveals an extensive infestation of Hackberry Wooly Aphids (Shivaphis celti), an Asian species that may have been brought to the U.S. by the importation of Chinese Hackberries (Celtis sinensis).  The Hackberry Wooly Aphid secretes lavish amounts of honeydew, so much that the leaves and twigs become coated with the sticky substance.  The honeydew acts as a perfect substrate for the fungus – usually called sooty mold –  which covers the leaves.  The fungus does not kill the tree, but does cause some leaf drop.  The honeydew, which is rich in carbohydrates, attracts ants ,which do not harm the aphids but instead benefit them by protecting against predators.

Celtis laevigata
Southern Hackberry
Hackberry Wooly Aphid

Celtis laevigata
Southern Hackberry
Hackberry Wooly Aphid

The photos below provide several more views of the leaves covered with sooty mold.  Also seen are orange lady beetles that are present in small numbers on the affected trees.

Celtis laevigata
Southern Hackberry
Sooty Leaves with Lady Beetle

Celtis laevigata
Southern Hackberry
Sooty Leaves with Lady Beetle

The lady beetles are the Asian Multicolored Lady Beetle (Harmonia axyridis), a major predator of the wooly aphids.  They are badly outnumbered on the affected trees and have very little impact on the course of the infestation.  It is ironic that this prey and predator relationship that began in Asia continues in a similar setting on a distant continent where both species were introduced (the aphids by accident; the lady beetles both intentionally and accidentally).

Celtis laevigata
Southern Hackberry
Asian Multicolored Lady Beetle

The Southern Hackberries are also parasitized by Leaf Petiole Galls, caused by the Hackberry Petiole Gall Maker (Pachypsylla venusta).  Petiole is the botanical term for the leaf stalk.  These galls are very common on hackberries and do not kill the trees, even when present in large numbers, as they often are.  Several examples are pictured below.

Celtis laevigata
Southern Hackberry
Hackberry Leaf Petiole Gall

Celtis laevigata
Southern Hackberry
Hackberry Leaf Petiole Galls

There are also small numbers of fruits on the trees.  They can be distinguished from the galls by their smooth, symmetrical surface, reddish tint, and  their position at the end of a stalk.   The galls are always located between a leaf and a twig and are never at the end of a stalk.

Celtis laevigata
Southern Hackberry
Fruit

The leaves on these hackberries, and those in the surrounding forests, are quite variable.  Some have few to no serrations while others are serrated on each margin.  Weakley’s Flora (May 2015) now recognizes the hackberries that have significant serrated leaf margins as Celtis smallii, and it is possible that these trees and others at Falls Lake may fall into that category.

Herb Amyx

 

The Neuse River Trail Heliotrope – Heliotropium indicum

Indian Heliotrope, Heliotropium indicum, is an introduced annual, probably from Tropical America.  It is uncommon in North Carolina, being absent from the Western Piedmont and the Mountains.  It is seen occasionally in small, isolated populations along the Neuse River Trail.  Unlike the garden Heliotrope (H. arborescens), which is known for its bright purple flowers and wonderful scent, Indian Heliotrope is considered an invasive and troublesome weed in many parts of the world.

Its small but beautiful flowers are reminiscent of Forget-me-nots, which are its close relatives in the Borage Family, the Boraginaceae.

Heliotropium indicum
Indian Heliotrope
Flowers

The flowers bloom in elongated, gracefully curved clusters, with the younger flowers occurring  near the end of the cluster, and the older flowers beginning to turn to  seed at the base.

Heliotropium indicum
Indian Heliotrope
Flowers

Photos of several populations are shown below.  Some are small and mingled with grasses at  ground level, and some are shrub-like, four to five feet tall.

Heliotropium indicum
Indian Heliotrope
Small Population

Heliotropium indicum
Indian Heliotrope
Large Population

Heliotropium indicum
Indian Heliotrope
Large Population

The typical plant form is illustrated by the two photos that follow.  The plants tend to be broad and low to the ground initially, rising in height as they begin to bloom.

Heliotropium indicum
Indian Heliotrope
Plant Form

Heliotropium indicum
Indian Heliotrope
Plant Form

The flower clusters can be elongated and very striking.   Their appearance gave rise to the common names Scorpion Weed and Scorpion Tail.

Heliotropium indicum
Indian Heliotrope
Elongated Flower Clusters

The leaves are broad and ovate, with a wrinkled upper surface, and are usually (but not always) alternate on the stem.

Heliotropium indicum
Indian Heliotrope
Leaf Front

Heliotropium indicum
Indian Heliotrope
Leaf Back

Heliotropium indicum
Indian Heliotrope
Stem

An interesting attribute of Heliotropes – their  flowers turn and follow the sun as it travels across the sky.  The name was based on the Greek for sun (Helios) and (trope) for turning or tropism.  Turnsole, an old English term with a similar meaning, is also another common name for Heliotrope, and is the common name used for Heliotropium indicum in Weakley’s Flora.

Herb Amyx