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Wednesday, November 7, 2018

Whorled Wonders

Great Plains Ladies Tresses

The spiral, which is a fundamental form in nature, is most splendidly illustrated in a genus of wild, native orchids called Spiranthes.  Commonly known as ladies tresses, the genus name comes from the Greek speira meaning ‘coil’ and anthos meaning ‘flower’, and refers to each species spirally arranged inflorescence.  The most predominant species of orchid found in Texas prairies, several members of this genus are colonizers of sparsely vegetated areas, appearing on newly disturbed sites such as roadsides and cleared fields, increasing in number until outcompeted by other vegetation.

Of the 15 native Spiranthes species in Texas, several are so similar in appearance that either a hand lens or microscope is often needed to distinguish one from another. To add to the confusion, many closely related species are also known to hybridize. However, Central Texas, the most common include the Great Plains Ladies Tresses (S. magnicamporum) and the Nodding Ladies Tresses (S. cernua).  

Great Plains Ladies Tresses has 2 to 4 narrow, grass-like basal leaves, up to 6 inches long, that are usually absent or withering during the flowering period.  The flower spike can range from 4 to 24 inches tall, and is made up of 12 to 54 small white tubular fragrant flowers, tightly or loosely spiraled, that nod abruptly from the base.  Blooming from September to November, it prefers calcareous grassland habitat, often growing in association with our native Seep Muhly.  In wet years, this orchid may appear in robust spikes numbering in the hundreds, and in dry years it may not flower at all.

Nodding Ladies Tresses has 3 to 5 narrow, grass-like, basal leaves, 8 to 10 inches long, and are typically present at flowering.  It has a flower spike that can grow from 4 to 19 inches tall, and consists of 10 to 50 small white tubular flowers, tightly or loosely whorled in 2 to 4 rows along the upper portion of the stem.  Blooming from late September through November (and sometimes even into December), it can grow on wet or dry sites, but prefers more acidic, sandy soils.

Flowers of Spiranthes orchids begin opening at the bottom of the inflorescence.

Like most orchids, the flowers of these Spiranthes species are resupinate, or twisting during development into an upside-down position.  In fact, the tendency of the flowers to droop slightly gives the Nodding Ladies Tresses both its common and species name, for cernua comes from the Latin and means ‘drooping.’  Unlike other closely related species, the flowers of the Nodding Ladies Tresses have little or no fragrance, but like other closely related species, the flowers are pollinated by bumblebees.  As with most Spiranthes, bumblebees start at the bottom and move upward on the inflorescence in search of nectar. Older flowers at the base of the flower stalk have more nectar, which makes them an efficient first stop for the foraging bumblebees.

As mentioned above, many Spiranthes are difficult to identify to species, and both the Great Plains Ladies Tresses and the Nodding Ladies Tresses are no exceptions.  In fact, Nodding Ladies Tresses is known as a compilospecies, which is defined as a genetically aggressive species that incorporates the heredities of a closely related species by hybridization through unidirectional gene flow, and may even completely subsume that species over time.  Now that’s a whorled wonder!


Saturday, November 3, 2018

Silent Flight



Eastern Screech-Owl
Owls have fascinated man from time immemorial – to some cultures they are symbols of wisdom, while to others they are harbingers of doom and death.  Adding to the mystique of these creatures is that they are mainly active at night, using their exceptional vision, acute hearing, and silent flight to stealthily hunt down their prey.

Common in Central Texas, the Eastern Screech-Owl is found in wooded suburban and rural areas and readily nests in tree cavities as well as man-made nest boxes.  A small owl 6-10” long with a wingspan of 19-24”, it has feathered ear tufts and is normally gray, brownish-gray, or less commonly reddish-brown.  The Eastern Screech-Owl eats a variety of small animals, and each night consumes from one-quarter to one-third of its own body weight.  It uses a soft trilling call to keep in contact with a mate or family members, and the male’s trill can advertise a nest site when courting a female or signal an arrival at the nest with food.  This owl also has a descending whinny, which is used to defend its territory.  Eastern Screech-Owl pairs are usually monogamous and remain together for life, although they will take a new mate when one dies.  In mid-April, the female lays 3-4 eggs on average, and the downy white owlets emerge from the nest by mid-May.

Great Horned Owl
Also common but much larger at 18-25” long with a wingspan of 40-57”, the Great Horned Owl prefers habitats of secondary-growth woodlands mixed with open meadows.  Often found perching next to an open area and nests in tree hollows, broken off snags, or nests made by other large birds.  It has prominent ear tufts spaced widely on its head, a brownish-gray body with dark barring, and a rusty facial disk edged in black surrounding each of its orange-yellow eyes. The Great Horned Owl has a broad diet of small mammals, birds, amphibians, and reptiles, and is the only animal the regularly eats skunks.  They have a large repertoire of sounds, but the most common is that of the male’s resonant territorial call ‘hoo-hoo hoooooo hoo-hoo’ that can be heard over several miles through the canyons on a still night. These owls are solitary in nature, only staying with their mate during the nesting season of January and February. Typically 2-4 eggs are laid and incubated solely by the female, until the young start roaming from the nest six to seven weeks later.  

The structure of an owl’s feather is the main reason they can fly so silently.  The leading edge of their primary wing feathers are serrated like a comb, which breaks down the turbulence into smaller, micro-turbulences.  The soft, tattered edges of their secondary feathers allow those small currents of air to pass through them and further reduce the turbulence behind their wings.  In addition, the velvety down feathers found in the wing linings and on their legs further dampen and absorb sound frequencies.  Together, these features allow the owl to greatly reduce the overall noise caused by the turbulence of air flowing over them as they fly.  

Thursday, October 4, 2018

Astonishing Acorns

Texas Red Oak is one of many types of oaks that produce
acorns in autumn
Famous for its oak trees, there are more than 50 species of oak native to Texas.  In our region of Central Texas, some of the most common include Live Oak (Quercus virginiana), Texas Red Oak (Quercus buckleyi), and Bur Oak (Quercus macrocarpa).  

A familiar tree with a stately growth habit, Live Oak is commonly 50 feet tall but with several large, twisting limbs that form a low, dense crown that can spread over 100 feet.  Its leaves are oblong in shape, leathery, 2 to 4 inches long and 0.5 to 2 inches wide.  Slow-growing but long-lived, it appears to be evergreen rather than deciduous since its old leaves fall just as new leaves emerge in the spring.  The annual acorns of this tree are dark brown and shiny, about 1 inch long and 0.5 inch wide, half covered in a gray, downy cup borne on a long stem. 

Live Oak Acorns
Texas Red Oak, also called Spanish Oak or Buckley Oak, is a small to medium tree to 35 to 70 feet tall, and its habitat is restricted to limestone ridges, slopes, and creek bottoms.  Its leaves are deeply lobed and it provides good shade in the summer and deep red color in the fall.  Its acorns are biennial, or maturing every other year, but when they do occur they are plentiful.  They can occur singly or in pairs, are up to 0.75 inches long and 0.5 inches wide often streaked with dark lines, and set in a shallow cup covering one-third to one-half of the fruit.

Texas Red Oak Acorns
A large, deciduous tree reaching a height of 80 feet or more, the Bur Oak has heavy branches that form an open, spreading crown, and leaves with highly variable lobes that can grow to 12 inches long and 6 inches wide.  But what is most characteristic is its’ distinctively large annual acorns, up to 2 inches long, set into a deep mossy-fringed cup that gives this species its common name.  In fact, an alternate common name is Mossycup Oak.  Bur Oaks have a medium growth rate, and develop a deep taproot that allows them to draw water and anchor the tree, even in drought conditions.

Bur Oak Acorn
The origin of the word acorn is dubious, as several sources are possible including Old Norse akarn meaning ‘fruit of wild trees’, Gothic akran meaning ‘fruit’, and Old English aecern meaning ‘mast or oak-mast.’  Mast is a term often applied to the fruit of oak trees, especially when they are used as food source for animals.

In Texas, oaks are important trees for wildlife as they provide acorns for food, shelter in their huge branches, and both food and shelter as they slowly decay.  For humans, oaks protect against soil erosion, buffer homes from strong winds, and provide true beauty in the landscape.  All of these benefits are derived from the simple yet astonishing acorns!



Wednesday, August 8, 2018

A Gainful Grape




Winter or Spanish Grape, Vitis cinerea var. helleri
Few plants have a higher ecological value to wildlife than the Winter Grape or Spanish Grape (Vitis cinerea var. helleri).  This hardy deciduous vine, which can grow to 72 feet long, is common in east, north, and central Texas, and is primarily distinguished from Mustang Grape (V. mustangensis) by the smooth surface on the underside of its leaves.  It makes for an excellent wildlife plant as its fruit is a food source to both mammals and birds, its dense climbing foliage provides cover and nesting habitat, and it is a host plant for more than a dozen species of moths. Common in woodland areas and thickets near streams and riverbanks, it thrives in part shade while clambering over other plants, even in the heat of summer.

When mature, the leaves of the Winter Grape are up to 4.5 inches long and 5 inches wide, and have white cobweb-like hairs only on the underside leaf veins.  Roughly heart-shaped, the leaves have two broad lobes, a pointed tip, and serrated edges.  While this vine does produce palatable, reddish-purple fruits in clusters up to 8 inches long that ripen from August to October, it is its leaves that provide the food for the larval stage of notable moths such as the Nessus Sphinx (Amphion floridensis), Vine Sphinx (Eumorpha vitis), Eight-spotted Forester (Alypia octomaculata), and Mournful Thyris (Thyris sepulchralis).  In addition to nectaring on flowers in the adult stage, these moths often pollinate those flowers at the same time.

Nessus Sphinx
Nessus Sphinx Caterpillar
Both the Nessus and Vine Sphinx are members of a family of moths called the Sphingidae, more commonly known as hawk moths, hummingbird moths, and sphinx moths. Generally speaking, these moths are named not just for their streamlined bullet-shaped bodies that have long narrow forewings and short hindwings, but also for their distinct behavior that comes in the form of swift, hovering flight. The leaf-feeding caterpillars or larva of these moths typically have a smooth body with a characteristic horn near their posterior end, hence the common name hornworm.  They pupate in an earthen cell or loose cocoon at or near the soil surface.  

Vine Sphinx
The Nessus Sphinx has a stout abdomen with two bright yellow bands and a tuft at the end.  The upperside of its wings are a dark red to chocolate brown, and its hindwings have a red-orange band with a yellowish fringe.  Its wingspan is 1.5 to just over 2 inches, flying during the day and at dusk, from March to May and July to September.  The Vine Sphinx has dark brown forewings with a striking pattern of thick, pale bands and three fine pinkish veins, and hindwings with a pink patch along the inner edge.  Its wingspan is 3.5 to just over 4 inches, flying mainly at dusk, from April to May and July to October.

Eight-spotted Forester
Eight-spotted Forester Caterpillar
Part of the Noctuidae family, the Eight-spotted Forester has black forewings with two pale yellow spots and inconspicuous metallic blue bands, and hindwings that are black with white spots at the base and in the middle.  Its black body has pale yellow at the base of the forewing, orange fringe on its front and middle legs, and like many species in this family, when perched it holds its wings above its body like a roof.  With a wingspan of 1.0 to 1.5 inches, it flies during the day, most commonly from February to May.  With black wings and body spotted with white, the Mournful Thyris is a member of the Thyrididae family, generally small moths with stout bodies and relatively short wings, that perch in a distinctive position with a raised body and outspread wings.  Its wingspan is just over 0.5 to just under 1.0 inch, flying mainly during the day, from April to August.  

Mournful Thyris

Whether you are looking for a hardy vine for your summer garden, or just a profitable plant for serving the needs of several species of native wildlife, look no further than the gainful grape!


Monday, June 4, 2018

Whiptails & Racerunners

Common Spotted Whiptail
Small to medium-sized slender lizards, whiptails and racerunners can be distinguished from other lizard species by their generally granular dorsal (topside) scales, larger rectangular ventral (underside) scales arranged in transverse rows, long tails, and forked, snake-like tongues. Additionally, these species belong to the genus Aspidoscelis, from the Greek aspido or ‘shield’ and skelos or ‘leg’, relating to their well-developed limbs that enable them to sprint at rapid speeds. Terrestrial and diurnal, these lizards are primarily carnivorous or insectivorous, actively foraging for food while temperatures are warm, and quickly skirting between objects for cover.  Of the 22 species occurring in the southwest, Central Texas is home to the Common Spotted Whiptail (Aspidoscelis gularis) and Six-lined Racerunner (Aspidoscelis sexlineata).  

Common Spotted Whiptail



The Common Spotted Whiptail has a brownish-green body with 7 to 8 longitudinal yellowish-white stripes and similarly colored spots in the margins.  Its tail is up to twice the length of its body, reaching a total length of just about 12 inches.  It is found in prairies, grasslands, rocky hillsides, dense thickets, and canyon bottoms, often near water.  Males are larger than females, having a red, orange, or pinkish throat and sometimes a blue or light blue belly.  Females have a white or cream-colored underside, and lay 1 to 8 eggs in July, typically in a separate chamber of their underground burrow, sometimes as deep as 11 inches.  These lizards scare easily and often retreat in a straight line, but can best be viewed from April through August when their insect prey are most abundant.

Six-lined Racerunner
Just over 10 inches long, the Six-lined Racerunner has seven light dorsal stripes with a greenish wash on the head and upper body that fades to brown posteriorly.  Males may also have a blue throat and belly, and juveniles often have more distinct stripes, lack the green wash, but have a bright blue tail. Females lay clutches of 1 to 6 eggs from May to August.  Associated more with sandy soils, this lizard can occupy a wide variety of habitats, including grasslands, riverbanks, floodplains, and juniper woodlands.  Spiders and grasshoppers are their chief prey, and adults actively forage during the day, but as summer temperatures rise by July, their activity becomes bimodal, peaking in the morning and late afternoon to avoid the hottest parts of the day.

Common Spotted Whiptail growing a new tail
Like many lizards, whiptails and racerunners have developed the ability to allow the tail to break free of the body when grasped by a predator. Called tail autonomy, this process involves wriggling the detached tail to distract the predator while the lizard itself is able to escape. Complex adaptations have evolved to enable the tail to be released along a series of fracture planes, which usually occur through weakened vertebrae, and not between them. Most amazingly, these species also have the ability to regenerate the tail, albeit slowly, so it can be lost again if necessary.



Friday, May 25, 2018

Distinctly Different Milkweeds

Pearl Milkvine
Much ado has been made of the more common and widespread milkweed species, but there are a handful of milkweed vines that are less common but more distinct, and just as useful as native host plants for Monarchs and related butterflies.

A fairly robust, twining vine 6 to 12 feet long growing in dry, light shade in thickets on rocky hillsides and woodland edges, Pearl Milkvine (Matelea reticulata) is best known for its heart-shaped leaves and flat, greenish-white flowers ½ to ¾ of an inch across with pearly, iridescent centers.   Also called Green Milkweed Vine, Net Vine Milkvine, and Netted Milkvine, its curious flowers have tiny white veins forming an intricate pattern on the surface of the petals, adding to their unusual look. In fact, ‘reticulata’ refers to this pattern, which mans ‘resembling a net or network’.  It blooms from April to July, especially in full sun, giving way to fairly large, interesting prickly follicles filled with seeds attached to silky threads.  This native species is a host plant to Monarch butterflies.

Plateau Milkvine

Both the Pearl Milkvine and Plateau Milkvine have prickly seed follicles
Often mistaken for Pearl Milkvine is Plateau Milkvine (Matelea edwardensis), endemic only to the Edwards Plateau of Central Texas.  This uncommon vine shares the same twining habit of Pearl Milkvine, but its leaves, while similar, generally have a somewhat wavy edge, and its flowers are bell-shaped instead of flat.  Additionally, its greenish-white flowers do not have a pearl center, and its petals are not solely reticulate-patterned, having parallel veins in their lower halves and centers, and reticulate or networked veins only on the edges or margins.  Blooming in April and May, this species can be found on gravelly soils in open woodlands, often climbing on other plants, and it is a native host plant for Queen butterflies.

Pearl Milkvine Flowers
Plateau Milkvine Flowers
Purple Milkvine
Usually found in the chalky soils of pastures and open ground, Purple Milkvine (Matelea biflora) has low-growing stems that radiate along the ground from a woody rootstock, and along with its opposite, triangular leaves, are covered with long, spreading hairs.  From March to June, pairs of star-shaped, five-petaled, dark purple-brown flowers rise from the base of the leaves, which gives this plant its other common name of Star Milkvine.  While its trailing stems can grow up to 2 feet long, it inhabits grassy areas and as such is often hidden and overlooked, except by Queen and Soldier butterflies who use it as their native host plant.

Talayote
Named for a small town in Chihuahua, Mexico, Talayote (Cynanchum racemosum) or Milkweed Vine is a climber that grows to 15 to 20 feet in full sun to part shade, and is a native host plant for both Queen and Soldier butterflies.  Talayote produces clusters of small cream and green flowers that are held above and among the heart-shaped leaves, blooming in the hotter months from summer into fall, and attracting a host of other small but beneficial pollinators.  Growing only in Central, South, and West Texas in the United States, this vine produces plump, smooth follicles 3 inches long, filled with silk-topped seeds, often remaining on the vine well into winter. 

Take the time to seek out and appreciate these lesser known members of the Milkweed family, as they are beautifully and distinctly different!

Tuesday, May 1, 2018

A Horse of a Different Color

Horsetail or Scouring Rush

Few plant species that grow naturally today have been around for over 100 million years, but one of the best known are plants in the genus Equisetum, which is the only living genus of the entire family of Equisetopsida, most commonly known as horsetails.  They are recognized as close relatives of ferns, typically growing in wetter areas with whorls of needle-like branches radiating at regular intervals from each single vertical stem.

The common name of horsetail is used for the entire group of plants, since the branched species resemble a horse’s tail.  In fact, the genus Equisetum comes from the Latin equus or ‘horse’ and seta or ‘bristle.’  Another common name is scouring rush, referring to the upright rush-like appearance of the plants, and the fact that the longitudinal ridges of the stems are coated with abrasive silicates, making them useful for scouring or cleaning metal items.  It is still used today as a traditional polishing material in Japan.

The primary species of horsetail that occurs natively in wet or moist areas of Texas, most commonly on the Edwards Plateau and in Blackland Prairie, as well as most of the non-tropical northern hemisphere, is Equisetum hyemale.  A spreading, reed-like perennial growing to 3 feet tall, each stem is evergreen, cylindrical, jointed, hollow, and about 1/4 of an inch in diameter.  In this species, the needle-like branches appear non-existent, but are actually small and fused around the stem at each joint or node, forming a blackish-green band or sheath.  Interestingly, the pattern of spacing of the nodes in these plants, which grow increasingly close together toward the apex, is precisely what inspired Scottish mathematician John Napier to discover logarithms in the late 16th century.

Dragonflies, like this Neon Skimmer, love to perch on the cones of
the horsetail’s upright stems.

Horsetail prefers open or wooded areas along streams, moist flats, and wet ledges. Like ferns and other related species, horsetails reproduce by spores rather than through seed-producing flowers. These spores are borne in cone-like structures at the tips of some stems, and are mostly homosporus, meaning of the same size and type.  The tiny spores have four elaters or structures that alter shape in response to changes in moisture, effectively acting as moisture-sensitive springs that assist spore dispersal through crawling and hopping motions once released from the cone.

Horsetails reproduce by spores borne in the cone-
like structures at the tips of some stems.

The upright, evergreen, segmented foliage of horsetail is an appropriate plant for a rain garden, pond edge, water feature, or area with moist soil, and is an excellent perching plant for dragonflies. While it can spread quickly by underground or underwater runners, it is easily kept in check by periodic pulling or by planting it in a container.  Few plants add as much interest or vertical structure to a wildscape as this living fossil, which is clearly a  ‘horse of a different color’!