European Water Clover (Marsilea quadrifolia) Visits North Carolina

Floating near the shore in a suburban lake in Wake County, North Carolina, is a colony of plants that look very much like a group of flooded shamrocks.  They are Marsilea quadrifolia, an aquatic fern commonly called European Water Clover or Water Shamrock.  Marsilea quadrifolia is an exotic fern, introduced from Europe.  It is well established in the Northeast, but is rare in the Southeast.    Below is a small group of plants floating at the surface of the water, and a close up of a single plant.

Marsilea quadrifolia European Water Clover

Marsilea quadrifolia
European Water Clover

Marsilea quadrifolia European Water Clover Close View

Marsilea quadrifolia
European Water Clover
Close View

Marsilea quadrifolia is considered a Waif in North Carolina (Weakley’s Flora, May, 2015).  A Waif in botanical terms normally refers to an introduced, alien plant that is unable over time to sustain a persistent population, and therefore does not become naturalized.   Thus it does not appear on the Flora of the Southeast distribution map for North Carolina or its surrounding states, but has evidently been seen in North Carolina sometime in the past.

As seen in the photos below, the lake provides a stable habitat, with shallow, quiet waters where the plant can root in mud and sand, relatively undisturbed by water level fluctuations.  The two trees in the immediate background of the first photo are Bald Cypress (Taxodium distichum).

Marsilea quadrifolia European Water Clover Habitat

Marsilea quadrifolia
European Water Clover
Habitat

Marsilea quadrifolia European Water Clover Colony Habitat

Marsilea quadrifolia
European Water Clover
Colony

When the water is shallow enough, the plants can stand erect, out of the water.  Note the fiddlehead (a fern’s curled frond) near the center of the picture.

Marsilea quadrifolia European Water Clover Erect Form

Marsilea quadrifolia
European Water Clover
Erect Form

In suitable habitats, the plants also have a land form, erect in the mud or sand.  See below.

Marsilea quadrifolia European Water Clover Land Form

Marsilea quadrifolia
European Water Clover
Land Form

Marsilea quadrifolia is a popular aquarium and water garden plant.  Its sudden appearance in a lake or pond is usually attributed to an accidental or deliberate introduction.  It has also been known to be disseminated by waterfowl.

Aquatic ferns represent only a tiny and comparatively insignificant portion of the aquatic plants in the Eastern U. S.  Two other aquatic ferns have been described in North Carolina.  Azolla caroliniana , the Eastern Mosquito Fern, is a tiny, native, floating aquatic fern, uncommon but widespread in the Southeast.   Salvinia molesta, called Giant Salvinia, is considered an exotic noxious weed, and is rare in the Southeast.

Herb Amyx

All photographs were taken on December 26, 2015.  Hard freezes and ice in January disrupted the plants and left only bits of debris.  The roots are cold hardy and the plants should return in the spring.

 

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Postscript to Frostweeds: Needle Ice

At the end of the third week in January, Central North Carolina experienced a severe winter storm, with snow, sleet, and freezing rain.  Warm weather began to prevail in the days that followed, and the ice and snow melted rapidly, leaving the ground saturated with moisture.   A series of overnight hard freezes then produced perfect conditions for natural ice sculptures to form, particularly ice extruded from porous soils, a phenomenon known as needle ice.  This phenomenon was mentioned briefly in the previous article describing natural ice sculptures produced by Frostweed – Verbesina virginica.  The conditions required for needle ice are the same as for plants that produce ice sculptures: temperatures above freezing below the ground surface interacting with air temperatures below freezing right at the surface of the ground.

The photo below is of an open, grassy field next to a parking lot.  What at first appear to be skiffs of remaining snow, are actually needle ice produced overnight from the hard freeze.

Needle Ice in an Open Grassy Field

Needle Ice in an Open Grassy Field

A couple of closer views follow.

Needle Ice in a Grassy Field

Needle Ice in a Grassy Field

Closer View of Needle Ice

Closer View of Needle Ice

The next photo shows more clearly the ice rising directly from the soil surface itself, often forming narrow ribbons.

Needle Ice Rising Directly From the Bare Soil

Needle Ice Rising Directly From the Bare Soil

A closer view of the needles of ice show grooves in the extruded ice very similar to those produced by plants.

Closer View of Grooved Ice Needles

Closer View of Grooved Ice Needles

Ice formations produced by soils are much more common than those of plant origin.  However, there are sometimes entire winters when the conditions are unfavorable for ground ice as well, particularly  during dry winters when there is not enough moisture at the surface of the soil.

Herb Amyx

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Frostweed (Verbesina virginica) “Blooms” in Central North Carolina

Frostweed – Verbesina virginica – is one of the very few plant species that can form unique and beautiful ice sculptures when winter conditions are favorable.  The weather in Central North Carolina this January produced perfect conditions for the creation of these ice formations, which are sometimes called “crystallofolia”.  The ground was saturated with moisture from frequent rains, and retained warmth from far above average temperatures in  December.  Hard overnight freezes in January created a layer of below- freezing temperatures at the surface of the soil, while just below the soil surface, the temperatures remained above freezing.  Moisture then began to freeze in the plant’s stem, and the subsequent ice was extruded from the stem.  Moisture from the roots was drawn into the stem to continue the ice formation.

Below are ribbons of ice from two different plants.

Verbesina virginica Frostweed Ice Ribbons

Verbesina virginica
Frostweed
Ice Ribbons

Verbesina virginica Frostweed Ice Ribbons

Verbesina virginica
Frostweed
Ice Ribbons

Both of the plants pictured above were small, first year plants, and only one bloomed this past summer.  Knowing the root system had to be limited, how did this much ice come from such a small plant?  One answer is that the ice ribbons are very thin, fragile, and insubstantial.  They crumble into pieces when touched and melt easily when the temperatures rise.  There really isn’t as much fluid there as it appears.  In addition, the soil saturation may enable the roots to continue to  withdraw moisture from the soil during the process.

Another interesting phenomenon is that ice sculptures can be produced a number of different times.  These plants have produced five consecutive frozen ice sculptures as of this writing.  The sculpture melts as the weather warms, and several days later, a new hard freeze triggers the extrusion of another complete ice formation.  Each new sculpture is virtually  identical to the previous one.

A closer look at an ice ribbon reveals a series of grooves or furrows in the surface of the ice.

Verbesina virginica Frostweed Surface Grooves

Verbesina virginica
Frostweed
Surface Grooves

It has been speculated that these grooves represent the vascular structures of the stem.  While this may be true, it is interesting to note that inanimate objects are also capable of producing similar ice structures.  Areas of soil or clay can produce needle ice, as can pieces of dead wood and  mulches.  Various parts of hollow metal fences can also produce  ice ribbons similar to those pictured above, including the grooves along the surface.

Several other plants species are known to be capable of producing ice sculptures, especially Cunila origanoides (Common Dittany), and several species of Pluchea (Camphorweeds).  However, the closest relatives to Frostweed do not produce ice sculptures: Verbesina occidentalis (Crownbeard) and Verbesina alternifolia (Wingstem), both extremely common in Central North Carolina.  The plant form of Wingstem in particular is very difficult to distinguish from Frostweed, both having similar alternate leaves and winged stems.   Evidently the structural factors required for formation of ice sculptures are highly specific and rare.  Frostweed leaves are pictured below.

Verbesina virginica Frostweed Leaves

Verbesina virginica
Frostweed
Leaves

White flowers are the major factor in separating Frostweed from its  close relatives Crownbeard and Wingstem, which both have yellow flowers.  Frostweed is also uncommon in Central and Eastern North Carolina.  See the Frostweed flowers below.  For a more detailed comparison of the three Verbesina species, see:

https://bwwellsassociation.wordpress.com/2014/09/19/flowering-now-in-central-north-carolina-verbesina-occidentalis-crownbeard-and-its-relatives/

Verbesina virginica Frostweed White Flowers

Verbesina virginica
Frostweed
White Flower

 

Herb Amyx

 

 

 

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Water Oak – Quercus nigra : Surprising Leaf Patterns

Water Oaks (Quercus nigra) are numerous and widespread throughout bottomland habitats in the Piedmont and Coastal Plain of North Carolina.  They are also found in lower numbers in many upland areas as well.  Although they are generally considered a medium sized tree, huge individuals can be seen in the Falls Lake area, particularly along the Neuse River.  They are tardily deciduous, meaning that they retain some of their leaves well into the winter, and younger saplings may have many green leaves left well into February.

Leaves of adults and most young saplings are small and fairly simple in shape: wide at the tip with a gradually tapering, narrow base.  The photograph below illustrates the variety of sizes and shapes most often seen in fall leaves from Water Oaks.

Quercus nigra Water Oak Fall Leaves

Quercus nigra
Water Oak
Fall Leaves

The leaves of many young saplings remain green deep into the winter and have a similar, simple pattern.  Although Water Oaks are members of the Red Oak family, the bristles can be hard to find on winter leaves.

Quercus nigra Water Oak Young Sapling

Quercus nigra
Water Oak
Young Sapling

Surprisingly, some young saplings have “…wildly different leaves than the typical adult form, frequently deeply lobed…” (Weakley’s Flora, May 2015).  These trees can be very difficult to identify since they are too young to have acorns, and the bark is not yet mature.  When first encountered, the leaves would not remind an observer of a Water Oak leaf.  See below.

Quercus nigra Water Oak Atypical Leaves

Quercus nigra
Water Oak
Atypical Leaves

The Sibley Guide to Trees, by David Allen Sibley, has excellent illustrations of these juvenile, atypical leaves on Page 196.  They range from deeply lobed, to narrow and symmetrical.  Sibley mentions that the uniformly narrow leaves can resemble those of Willow Oak (Quercus phellos), but are always a small minority of the leaf shapes on the tree.  All of the leaves pictured above came from the same branch of a juvenile Water Oak.

As with other members of the Red Oak family, Water Oaks readily hybridize with other closely related family members, creating intermediate trees that require specialists to identify.

Herb Amyx

 

 

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Southern Red Oak – Quercus falcata : Fall Leaf Patterns

Quercus falcata, the Southern Red Oak, is one of the commonest upland oak species in the Central Piedmont of North Carolina.  It is a member of the red oak group, which is characterized primarily by the bristles at the end of the leaf lobes, and by acorns that require two years to mature.  The Southern Red Oak has a prodigious array of leaf patterns, a characteristic that is difficult to appreciate in the spring and summer when the leaves are high on the tree, but is conspicuous when the leaves are directly  under foot in the late fall and winter.

The species name falcata is descriptive of the majority of mature leaves, falcate meaning curving and tapering gradually to a point.  The fall leaves pictured below are easily recognized, and are most commonly associated with the Southern Red Oak.  They are shown with the reverse side up to illustrate the tawny, light color of the underside, which remains fuzzy to the touch even after the leaf dies and is shed.

Quercus falcata Southern Red Oak Falcate Leaves

Quercus falcata
Southern Red Oak
Falcate Leaves

Quercus falcata Southern Red Oak Falcate Leaves

Quercus falcata
Southern Red Oak
Falcate Leaves

This oak has quite a repertoire of intermediate shapes and sizes that are not always immediately recognizable as Southern Red Oak.  A few of them are shown below, but there are many more than this photo illustrates.  These leaves are shown topside up.

Quercus falcata Southern Red Oak Intermediate Leaf Shapes

Quercus falcata
Southern Red Oak
Intermediate Leaf Shapes

Small, immature trees have very different leaf patterns, most of which could be described as tri-lobed, with the tips of the leaves having a rounded, blunt appearance.   Completely ovate leaves can also be found, a shape not well known or described.  The leaves below came from a young, 15 foot Southern Red Oak , and  all the leaves were taken from the same branch.

Quercus falcata Southern Red Oak Leaves of an Immature Tree

Quercus falcata
Southern Red Oak
Leaves of an Immature Tree

The leaf shapes illustrated above are  not restricted to saplings, but can sometimes be seen on trees of medium height.  The ovate leaves on the lower right in the photo still have the characteristic bristles, approximately where the three lobes would be if they were present.  See below.

Quercus falcata Southern Red Oak Ovate Leaf with Bristles

Quercus falcata
Southern Red Oak
Ovate Leaf with Bristles

Blackjack Oaks, Quercus marilandica, are much less common than Southern Red Oaks, but do appear sporadically in the same areas.  Their leaf shapes are much less diverse, but can sometimes be confused with the immature Southern Red Oaks.  A few representative Blackjack Oak leaves are pictured below.

Quercus marilandica Blackjack Oak Typical Fall Leaves

Quercus marilandica
Blackjack Oak
Typical Fall Leaves

Three tri-lobed leaves from a young Southern Red Oak are at the top of the next picture, with two Blackjack Oak leaves below them.  These leaves were taken from young trees directly adjacent to each other, with some of the branches intertwined.  It is easy to see how they could be confused.

Leaves of Southern Red Oak at the Top, with Blackjack Oak Leaves Below

Leaves of Southern Red Oak at the Top, with Blackjack Oak Leaves Below

While the leaves of the Blackjack Oak pictured above are coarsely lobed, they are usually shallower than the lobes of the Southern Red Oak above.  In addition, the tips of the Blackjack Oak leaves are wider proportionally than the Southern Red Oaks.

The Pagoda or Cherrybark Oak (Quercus pagoda) has  probably the most difficult leaf to distinguish from the Southern Red Oak.  In fact, at one time the Pagoda Oak was classified as a variety of the Southern Red Oak.  Below are typical leaves of the Pagoda Oak.

Quercus pagoda Pagoda Oak Typical Leaves

Quercus pagoda
Pagoda Oak
Typical Leaves

Below is a comparison between two Southern Red Oak leaves (on the left) and two Pagoda Oak leaves (on the right).

Southern Red Oak Leaves on the Left vs. Pagoda Oak Leaves on the Right

Southern Red Oak Leaves on the Left vs. Pagoda Oak Leaves on the Right

The base of the Southern Red Oak leaves tend to be rounded while the base of the Pagoda Oak leaves tend to be sharp and angular.  The Pagoda Oak leaves also  tend to be more symmetrical, with lobes often opposite each other, while regular symmetry is not common in Southern Red Oak leaves.  When distinguishing these two trees, it helps to look at many leaves rather than just a few as pictured above.

Leaf shape depends on many variables and is seldom used alone to distinguish tree species.   Location on the tree (sun vs. shade), soil type and habitat, rainfall or lack of it, and most importantly genetics, all affect leaf shape.

Herb Amyx

 

 

 

 

 

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Kudzu Swallows a Local Greenway

The word “neglect” always carries a negative connotation.  It is worse than just ignoring, for neglect takes place over a period of time and usually leads to harmful consequences.  Neglect is perhaps the most important feature of Kudzu invasions.  Kudzu thrives on neglect.

Kudzu (Pueraria montana var. lobata) is perhaps the best known invasive plant in the South.  A member of the bean family (Fabaceae),  and a native of Asia, it is a rapidly growing, twining vine with large, floppy leaves composed of three leaflets.  Its prodigious summer growth rate (up to a foot a day) is legendary.

The greenway pictured below is located near Falls Lake and the town of Wake Forest, North Carolina.  It was built by a commercial developer who began a project on a large parcel of land, with the greenway circumscribing one edge of the property.  The project fell through, and the parcel was abandoned, leaving no one responsible for the greenway.

Faced with no opposition, Kudzu and other weeds began to overtake the greenway.  These photos were taken in September, 2013.  Below, Kudzu is flowing down a section of the asphalt trail like green lava.

Kudzu Covering Abandoned Greenway

Kudzu Covering Abandoned Greenway

Next, Kudzu shrouds a slope, with a pedestrian underpass partially hidden but still visible in the center.

Kudzu Covering the Slopes and Sides of an Abandoned Greenway

Kudzu Covering the Slopes and Sides of an Abandoned Greenway

Hanging vines of Kudzu, Japanese Honeysuckle, and English Ivy begin to form a hanging garden down the brick greenway wall.

Hanging Vines on Greenway Wall

Hanging Vines on Greenway Wall

An upper portion of the trail has large numbers of Dogfennel (Eupatorium capillifolium) and other weeds growing on the sides while trailing vines of Kudzu can be seen making their way up the edge of the path.

Dogfennel and Kudzu Along a Portion of the Greenway

Dogfennel and Kudzu Along a Portion of the Greenway

In photos taken this November, 2015, some changes are evident.  Kudzu vines have grown all the way to the top of many trees bordering the greenway.  The asphalt trail is mostly covered with a thatch of Kudzu vines which have resisted the traffic from mountain bikes, runners and walkers.

Asphalt Trail Covered by Kudzu Vines

Asphalt Trail Covered by Kudzu Vines

Growth of the brambles, young pines, and woody plants bordering the trail has created a corridor of plants covered by kudzu vines up to six feet tall.  Only mountain bikes and foot traffic have kept the corridor from closing off the path.

Narrow Corridor Formed on Path From Growing Plants and Kudzu

Narrow Corridor Formed on Path From Growing Plants and Kudzu

The hanging gardens have proliferated and now close off most of the brick wall.

Hanging Vines Have Covered Most of the Greenway Wall

Hanging Vines Have Covered Most of the Greenway Wall

This abandoned greenway will eventually  serve as a connector to join together a larger greenway system.  When the time comes to clear the mass of plants, the Kudzu showing above the ground will be a big task.  But the more difficult problem will be the large, central root crowns which have had time to gain size and strength, and to anchor deep roots.  In cases like this, it takes time and persistence, sometimes several seasons, to remove or kill the crowns.

Herb Amyx

 

 

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North Carolina’s Rare Serpentine Aster – Symphyotrichum depauperatum

Symphyotrichum depauperatum, the Serpentine Aster, may be the most unusual native aster in North Carolina.  It is extremely rare, with a state ranking of  Critically Imperiled, and a status of Endangered .    In addition, it is found at only a single site (Granville County) in North Carolina.  Also remarkable and unique is its occurrence on a diabase glade in North Carolina.  All other populations in North America are found on serpentine barrens, primarily in Maryland and Pennsylvania.  Its occurrence on serpentine soils (more about this later) gave rise to the common name of Serpentine Aster.

Symphyotrichum depauperatum is a diminutive, fragile aster with thin stems, and small flowers.  The flowers have 7 to 14 white rays and yellow discs.  The leaves on the flowering stems are tiny, narrow and sharply pointed.  See below.

Symphyotrichum depauperatum Serpentine Aster

Symphyotrichum depauperatum
Serpentine Aster

The plant above is shown below with a hand in the photo to demonstrate its small size.

Symphyotrichum depauperatum Serpentine Aster

Symphyotrichum depauperatum
Serpentine Aster

Below is another fully developed aster against the backdrop of a camera case.  The photo shows a typical blooming form of the Serpentine Aster.  The camera case is 8 inches tall.

Symphyotrichum depauperatum Serpentine Aster

Symphyotrichum depauperatum
Serpentine Aster

The basal leaves in this group of asters were quite variable, but tended to be rounded in the newer leaves, and lanceolate to spatulate in the more developed leaves.  The first photo below shows the basal leaves just emerging and the second photo shows an older aster whose basal leaves are mature.  Also note the ciliate (fine hair) leaf margins  in the two photos below.

Syphyotrichum depauperatum Serpentine Aster Basal Leaves

Symphyotrichum depauperatum
Serpentine Aster
Basal Leaves

Symphyotrichum depauperatum Serpentine Aster Basal Leaves

Symphyotrichum depauperatum
Serpentine Aster
Basal Leaves

As with many perennial asters, the basal leaves wither when the aster begins to bloom, but new basal leaves develop to take their place.  Red arrows in the photo below show the basal leaves that have just withered, underneath the newly arrived leaves.  The ciliate leaf margins are still visible on some.

Symphyotrichum depauperatum Serpentine Aster Withered Basal Leaves

Symphyotrichum depauperatum
Serpentine Aster
Withered Basal Leaves

As mentioned above, the occurrence  of the Serpentine Aster in a diabase glade is very unusual.  Serpentine barrens are harsh and demanding ecosystems that arise on serpentine soils derived from underlying serpentonite rock.   In the U.S., most occur in Maryland, Pennsylvania, and California.  They are characterized by shallow soils with a low nutrient content, low water holding capacity, high magnesium and low calcium (an unfavorable ratio for plants), and high levels of metals like chromium and nickel.   Thus it is no surprise that the species name for the Serpentine Aster, depauperatum, is derived from the Latin for impoverished or starved.

While diabase soils can also be shallow and have a high Magnesium content, they generally have an adequate nutrient content and sufficient calcium for a favorable magnesium/calcium ratio.  The Serpentine Aster’s presence at this site in North Carolina remains somewhat of a mystery.

Herb Amyx

For more on serpentine habitats see:

Intraspecific Variability in the Response of Certain Native Plant Species to Serpentine Soil.  Arthur R. Kruckeberg, American Journal of Botany, Vol 38, No 6 (June, 1951) pp 408-419

Brian Anacker. 2014. The nature of serpentine endemism. American Journal of Botany. 101: 219-224.

 

 

 

 

 

 

 

 

 

 

 

 

 

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