Resilient Ruellias

Ruellias flower throughout the heat of summer.

Are you looking for native, non-aggressive flowering plants that are perfectly adapted to our central Texas limestone soils and extreme summer heat? Then look no further than some of our local species of Ruellia, also informally but incorrectly called wild petunias. They include Drummond’s Ruellia (Ruellia drummondiana), Hairy Ruellia  (Ruellia humilis), Metz’s Ruellia (Ruellia metziae), and Violet Ruellia (Ruellia nudiflora).

Drummond's Ruellia

A Texas endemic, Drummond’s Ruellia has ovate, fine-haired leaves and purple to dark lavender stalkless (sessile) blooms arising from the leaf axils (axillary). It is prominent on the Edwards Plateau and in and around Austin, and blooms from June to November. Hairy Ruellia, also called Fringeleaf Wild Petunia, has conspicuously hairy oval leaves with pointed tips and hairy margins, and purple to pale purple axillary, sessile blooms. It is highly drought-tolerant and is widespread in open prairies on limestone soil, where it blooms from May to September.

Hairy Ruellia

Metz's Ruellia

Metz’s Ruellia or White Ruellia is distinct in that it features uncommonly white or pale-throated stalked (peduncled) blooms in a branched structure (panicle) at the tops of stems (terminal), and oval leaves on long leaf bases (petioles). It thrives on limestone outcrops and in open woods, and blooms from June to August. Violet Ruellia, also called Common Wild Petunia, is one of the most ubiquitous of all these species, with a similar arrangement of peduncled blooms in a panicle on the terminal ends of stems, but the blooms are purple to violet-blue. The leaves are oval, smooth and essentially hairless (glabrous) with somewhat wavy margins, and the blooms occur from April to October.

Violet Ruellia

Mexican Petunia (non-native)

Unlike the invasive, non-native Mexican Petunia (Ruellia simplex) that is sold in many nurseries, these resilient native species are well-behaved. They provide a bounty of successive summer blooms while other flowering plants are wilting in the heat. Their flowers open in the morning and fall off by evening, and they can be correctly identified by the structure of the inflorescence (axillary or panicled), leaf texture (waxy, hairy, or fringe on margins) and leaf shape (ovate, oval, or lance-shaped). The Hairy Ruellia and Violet Ruellia species are also host plants for Common Buckeye and White Peacock butterflies.

The genus Ruellia was named after a French botanist and physician, Jean Ruelle, who lived during the Renaissance Period. He was noted for his 1536 publication in Paris of De Natura Stirpium, a Renaissance treatise on botany, which included detailed descriptions not only of a plant species' habit and habitat, but also the smell and taste of each.

Neither Hummingbird nor Bumblebee

 

Hummingbird or bumblebee?  Neither!

Take a closer look when you see what you think is a small hummingbird hovering about and nectaring on the tubular flowers in your garden.  It just might be a Snowberry Clearwing (Hemaris diffinis), one of our more common hummingbird moths.  

Moths in the genus Hemaris are often generically called hummingbird moths, due to their ability to fly and move just like hummingbirds. They are rather plump moths, and the tip of their abdomen opens a bit like a fan. Many are brown or black with some yellow, so they are also good bumblebee mimics. Several species have clear wings, as they lack as many wing scales as other lepidopterans, and they actually lose the ones they do have shortly after they emerge due to their highly active flight tendencies.  

This adult Snowberry Clearwing just emerged from a winter spent in leaf litter,
still with all the scales on its wings.

The Snowberry Clearwing is about 1.25 to 2 inches in length, with a yellowish thorax above, a black abdomen with a yellowish band near the tip often split in two, and the namesake clear wings. Like other hummingbird moths, they generally fly during the day, but may continue into the evening if they have found a particularly good nectar source. Their proboscis or sucking mouthpart is quite long, so they prefer to sip from tube-shaped flowers. 

An adult Snowberry Clearwing showing its yellow thorax, black abdomen with a
yellow stripe, and signature clear wings.

The adults start flying in March after emerging from the leaf litter beneath their host plant where they spend the winter as a pupa protected by loose silken cocoon.  Females attract males by broadcasting a pheromone from the glands at the tip of the abdomen, and after mating, they lay individual, tiny, round green eggs on the underside of the leaves of the host plant.  In the south, they typically produce more than one generation each summer, flying well into November.

The common name for the Snowberry Clearwing comes from the fact that it was first described in 1836 in the northeast, where it uses Common Snowberry (Symphoricarpos albus) as a host plant, a native plant in the Honeysuckle family that grows in the northern half of North America. In the southern US, the preferred native host plant for this moth is Coral Honeysuckle (Lonicera sempervirens), which can be purchased at most native plant nurseries.  It is a high-climbing, twining vine to 20 feet long, with smooth, paired semi-evergreen leaves and clusters of red, tubular flowers.  In the wild, they also use our native White Bush Honeysuckle (L. albiflora), which is more shrub-like with twining branches that have smooth, paired deciduous leaves and clusters of creamy white tubular flowers.

Coral Honeysuckle

White Bush Honeysuckle

The larva or caterpillars of the Snowberry Clearwing are commonly called hornworms, due to the horn-like projection on their posterior end.  They are up to 2 inches long, blue-green above and yellow-green along the sides, with black spots and a black horn.  Uncommonly, they can also take a brown form with the same black spots and horn.  They match the foliage of their host plants so well that they are often very difficult to find. 

Snowberry Clearwing larva, green form.

Snowberry Clearing larva, brown form.

An Abundance of Acorns

Texas Red Oak displaying fall color.

Texas is famous for its oak trees, with over 50 different species found in the Lone Star State.  Each of these oak species produce acorns, also called oaknuts or mast, which is a collective term for fruits or nuts.  The word acorn is related to Gothic term akran which has been interpreted to mean ‘the fruit of the unenclosed land.’  When oaks are dominant in the landscape, as they are here in central Texas, they play an important role in the ecology of the forest.

Acorns usually contain one seed enclosed in a tough, leathery shell, and have a cup-shaped cap or cupule. Depending on the oak species, acorns can take from 5 to 24 months to mature.  As a general rule, acorns mature in late summer, turning green to brown, and start falling from oak trees in September and October.  Acorns produced by trees in the red oak family (such as Texas Red Oak, Quercus buckleyi) take two years to mature, while acorns produced by trees in the white oak family (such as Bur Oak, Quercus macrocarpa) only take one year. 

Texas Red Oak Acorns

Some years, known as mast years, trees produce copious amounts of acorns with smaller crops in the years between.  Scientists have proposed a range of explanations for the mystery of what might trigger a mast year, but they do know that it is not resource-driven as annual rainfall and temperature fluctuations are generally much smaller in magnitude than the variation in the crop sizes of acorns.  Some scientists hypothesize that masting trees are trying to maximize pollination efficiency.  If these trees flower and release pollen at the same time in order to increase their chances of reproduction, since large amounts of pollen correlate with larger amounts of germination, they ultimately produce more acorns.  Large, occasional outputs of seeds like acorns appears to be more favorable than frequent, smaller outputs.

Bur Oak acorns are our largest acorns.

Boom and bust years of acorn production actually benefit oak trees from an evolutionary perspective, because acorns are an important, highly nutritious food source for many animals including squirrels, mice, turkeys, blue jays, pigeons, ducks, deer, and bears.  In a mast year, these animals can’t consume all of the acorns produced, so some are left to germinate and grow into future oak trees.  In leaner years, animal populations are kept in check so there are fewer animals to eat the acorns in the mast years.  Over time, a higher proportion of acorns survive to become oak trees.

Copious amounts of acorns are produced in a mast year.

Too heavy for wind dispersal, acorns need other ways to spread beyond the mother tree into a suitable area for germination.  Jays, squirrels, and some woodpeckers serve as the main dispersal agents, as they gather and hoard acorns in caches.  While they are remarkable in creating mental maps of their cache locations, these animals rarely eat every single acorn, so a small number manage to germinate and produce the next generation of oaks.

The Blue Jay is one of many species that cache acorns.

As autumn arrives and acorns mature and fall from our oak trees, think of the potential in the abundance of acorns produced.  As Henry David Thoreau once wrote, “Every oak tree started out as a couple of nuts who stood their ground.”  

Beat the Heat

 

Flame Acanthus is a hot weather bloomer.

The heat of the Texas summer is enough to make everything wilt, but there are some native plant species that truly thrive in these unrelenting temperatures and drought-stricken conditions.  These plants include Turk’s Cap (Malvaviscus arboreus var. drummondii), Flame Acanthus (Anisacanthus quadrifidus var. wrightii), Violet Ruellia (Ruellia nudiflora), and Western Ironweed (Vernonia baldwinii).

Turk’s Cap, also known as Drummond’s Turk’s Cap, Wax Mallow, Mexican Apple, Manzanita, and Sleeping Hibiscus, is a spreading shrub to 4 feet high, with large green leaves on upright stems.  Bright red flowers atop the stems are twisted into a whorl from which protrude red stamens.  These flowers are a natural source of nectar for hummingbirds and butterflies, and it is a host plant for the Turk’s-cap White-Skipper butterfly.  The resulting fruit is red and marble-sized, and edible for animals and humans alike. Turk’s Cap is the perfect plant to grow under trees that tend to shade out non-native turf grasses, as they form a natural cover and provide much needed color from May all the way to November.

Turk's Cap

Turk's Cap fruit

Turk's-cap White-Skipper

An airy, spreading shrub to 5 feet tall, Flame Acanthus has tender lance-shaped green leaves and tubular red flowers that open to 4 lobes and occur along terminal spikes.  Blooming in full sun from June to October, it attracts both hummingbirds and butterflies, and is also known as Hummingbird Bush, Wright’s Acanthus, and Mexican Flame.  It is the host plant for the Crimson Patch, Elada Checkerspot, and Texan Crescent butterflies. The fruit is a small, hood-shaped capsule with seeds attached to a hooked stalk that helps to eject them from the capsule when it dries and splits open.

Flame Acanthus

Flame Acanthus seed capsule

Crimson Patch

Violet Ruellia is an erect herb that is woody at the base with few branches, growing to 2 feet tall.  The dark green leaves are oval-shaped, and the trumpet-shaped violet flowers at the ends of stalks open at sunrise and fall from the plant in early afternoon, from March all the way through October. Also called Wild Petunia, it does well in sunny areas and is a host plant for the Common Buckeye butterfly.  One of its’ subspecies is a host plant for the Malachite butterfly, a south Texas species rarely seen in central Texas.

Violet Ruellia

Common Buckeye

Often stout and forming colonies 5 feet high, Western Ironweed has hairy unbranched stems, large green leaves with serrated edges, and loose clusters of bright purple blooms at the apex of each stem.  From July to the first frost, these fuzzy blooms provide nectar for various types of pollinating insects and the seeds nourish several species of birds.  Also called Baldwin’s Ironweed, it is the host plant for the Parthenice Tiger Moth.  While this species’ growth can be aggressive, it flourishes if allowed to spread in larger, open, sunny areas.

Western Ironweed

These native species can (and often should) be pruned back in winter as they can get too leggy.  They have low water needs once established, and can tolerate hot temperatures and still continue to bloom.  They are the perfect plants to beat the heat, benefit our local wildlife, and provide much needed color in your own native summer garden!

Undervalued Vines

  The uncommon Plateau Milkvine is often mistaken
for the more common Pearl Milkvine (above).

Every species of native plant has its purpose, and while many are valued by humans for their fragrant flowers and foliage, those that are valued for their role in keeping the earth’s nutrient cycles intact should be regarded as having the highest value.  Those nutrient cycles need to be protected through plant preservation or restoration, as they are what provides nourishment for the lifecycles of our native wildlife and protects the health of our ecosystems.

Even among those folks who are familiar with many native plants that perform this role, there are some little-known species that are often overlooked and under appreciated.  In Central Texas, there are a few species of vines in the Milkweed family that many fail to notice, including Star Milkvine (Matelea biflora), Plateau Milkvine (Matelea edwardsensis), and Bearded Swallow-wort (Cynanchum barbigerum).  

Star Milkvine, also called Purple Milkweed Vine, is a relatively common vine that grows in pastures, prairies, and other open ground, usually in chalky soil throughout Central and North Texas.  This small, trailing vine to 2 feet has five-petaled, star-shaped, deep purplish-brown flowers that are 0.5 inches wide.  Blooming from March to June, the flowers occur in pairs along the trailing stems that radiate from a central rootstock, and arise from the axils of the opposite, triangular leaves.  The flowers, leaves, and stems are all quite hairy, as is true of many members of the Milkweed family.  Its habit is to grow low among grasses, often in areas that are mowed, so it is frequently passed over by humans, but is a useful host plant for Queen and Soldier butterflies and a nectar plant for several species of bees.

Star Milkvine has low-growing stems that radiate out
from a central rootstock.

The unusual flowers of Star Milkvine occur in pairs.

Soldier

Sometimes mistaken for the more common Pearl Milkvine, Plateau Milkvine is a vine to 3 feet that is 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 0.7 inch wide 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 vine can be found on gravelly soils in open woodlands, often climbing on other plants, and is a native host plant for Queen butterflies.  Due to indiscriminate land clearing, this plant is listed as ‘vulnerable’ in terms of its conservation status in Texas.

Plateau Milkvine is a rare cousin to Pearl Milkvine.

The flowers of Plateau Milkvine distinguish it
from Pearl Milkvine.

Queen

Growing up to 8 feet long, Bearded Swallow-wort, also called Thicket Threadvine and Aphid Vine, is a delicate vine that climbs on shrubs and small trees in open woodlands, in thickets, and along roadsides and fencerows in the Edwards Plateau and South Texas. It has small glossy lance-shaped, opposite leaves to 2 inches long, and from March to August, tiny creamy-white flowers appear in loose clusters from the leaf axils.  These flowers are 0.25 inches wide, bell-shaped, and have five distinctively hairy or ‘bearded’ recurved petals.  Five similar species in this genus are present in Texas, but this is the only one with ‘bearded’ flower petals.  Aphids are often found on this plant, giving rise to one of its other common names, and it is the host plant for the Obscure Sphinx Moth (Erinnyis obscura).

Bearded Swallow-wort is a rather delicate climbing vine.

The fringed or 'bearded' flowers
of Bearded Swallow-wort.

Obscure Sphinx

Whether it is due to their scarcity or diminutive stature, it is easy to miss these vines.  While they might be undervalued by humans, they are quite valuable to our native wildlife!

Introduced Invaders

 

Closeup of a Bastard Cabbage bloom

Spring brings new growth to all types of plants, including those species known as non-native invasives.  Non-native plants, also called exotics, are defined as plants ‘growing in a place that is not the region where they naturally grow’, and invasive plants are defined as plants that are ‘both non-native and able to establish on many sites by growing quickly and spreading to the point of disrupting native a plant community or ecosystem’.  

While plants that are non-native or invasive can be problematic, when a plant is both non-native and invasive, it can quickly outcompete native plants.  These invaders can produce copious amounts of seed easily transmitted by wind, water, or birds, thrive on poor or disturbed soils through aggressive root systems, have an early growth season or produce growth-inhibiting chemicals, and ultimately disrupt natural nutrient cycles of wildlife.  

In Central Texas, the species that cause the most harm to the local environment include Ligustrum (Ligustrum sp.), Nandina (Nadina domestica), Chinaberry (Melia azedarach), Chinese Tallow (Triadica sebifera), Bastard Cabbage (Rapistrum rugosum), and Japanese Honeysuckle (Lonicera japonica).  Most of these species have been introduced to the United States via the nursery trade as ornamentals, and unfortunately many are still sold today.

Ligustrum or Glossy Privet

Ligustrum or Glossy Privet, native to China, Japan, and Korea, is an invader of roadsides, thickets, open woodlands, and disturbed areas.  This evergreen tree to 40 feet has simple green, glossy pointed leaves.  It is widely cultivated and frequently escapes to invade and dominate the woodland understory, as its abundant purple-blue fruits are easily spread by birds and other animals.

Nandina or Heavenly Bamboo

Nandina or Heavenly Bamboo, native to China and Japan, is an invader of landscapes, roadsides, and other cultivated areas.  This erect, multi-stemmed shrub to 8 feet has compound green leaves to 12 inches long that are tinged with red in winter.  It spreads by escaping cultivation through underground root sprouts and animal-dispersed seeds, and quickly forms a colony.  Additionally, its shiny red fruits are toxic to small children, pets, and some grazing animals.

Chinaberry

Chinaberry, native to parts of Asia, is an invader of roadsides, thickets, open woodlands, and disturbed areas.  This deciduous tree grows up to 50 feet and has compound green leaves to 24 inches long.  Lavender blooms distinguish it from the similar but native Western Soapberry (Sapindus drummondii), which has white blooms.  It spreads on site via fast-growing root sprouts and over longer distances via bird-dispersed seeds from its golden-yellow fruits.

Chinese Tallow

Chinese Tallow, native to China and Japan, is an invader of cultivated landscapes and other moist areas.  A deciduous tree that grows to 60 feet, it has diamond-shaped leaves with elongated tips that turn orange-red in fall.  It reaches reproductive age in as little as three years, producing prolific amounts of seed that is readily transported by birds and water.  It is difficult to eradicate once established, and can effectively transform a native habitat into a monoculture.

Bastard Cabbage

Bastard Cabbage, also called Common Giant Mustard and Turnipweed, and native to southern Europe, northern Africa, and western Asia, is an invader of meadows, fields, roadsides, and other disturbed areas.  This many-branched herb grows to 5 feet, with clustered of small lemon-colored flowers at the tips of branches.  Its seeds germinate early in spring, quickly covering the ground with a dense blanket of leafy rosettes that block sunlight from reaching seedlings of native plants.  It reseeds rapidly and forms large monocultures.

Japanese Honeysuckle

Japanese Honeysuckle, native to Japan, is an invader of thickets on disturbed floodplains, creeks, and river banks.  This climbing, sprawling vine grows to 80 feet, with simple oval leaves and tubular white flowers that turn butter-yellow as they age.  Choking out other species by girdling or by blocking out sunlight through overgrowth, its plentiful seeds are easily dispersed by birds and other wildlife.  It is not to be confused with the native, much less aggressive White Bush Honeysuckle (L. albiflora). 

Replacing these non-native invasive plants with native plants help restore natural habitat, preserve and produce much-needed soil, protect fragile waterways from erosion, and as a result, keep vital nutrient cycles intact for all forms of wildlife.  Natives are already adapted to our soils and climate so they require little to get established, are naturally hardy and disease-free, and they provide food, shelter, and places to raise young for local insects (especially pollinators), birds, and other wildlife.  Natives are also a beautiful reminder of the unique natural heritage of Texas, so please consider to replacing your non-native invasive plants with natives today.  Once established, you’ll be amazed at how they bring your landscape to life!

INVADER                                NATIVE REPLACEMENT(S) - some ideas...

Ligustrum species                    Escarpment Black Cherry, Mexican Plum

Nandina                                    Yaupon, Possumhaw, Rusty Blackhaw Viburnum, Sumacs

Chinaberry                                Western Soapberry, Oaks, Redbud, Mexican Buckeye

Chinese Tallow                          American Sycamore, Black Willow, Texas Ash

Bastard Cabbage                      Mistflowers, Salvias, Sages

Japanese Honeysuckle            White Bush Honeysuckle, Coral Honeysuckle

Beguiling Bloomers

Pink Stonecrop

Springtime in Central Texas brings a host of familiar wildflowers blooming in meadows and woodlands, and along grassy roadsides. But each year the seasonal conditions may vary, based largely on the timing and amount of rainfall.  While many species are widespread from year to year, some appear infrequently, others only in certain habitats, and many go almost completely unnoticed.

Clasping Venus’ Looking-glass

Clasping Venus’ Looking-glass or Clasping Bellflower (Triodanis perfoliata) is a distinctive annual that can be found growing in open often disturbed areas, sometimes appearing even in cultivated flower gardens.  In April and May, violet-blue, 5 petaled, wheel- to bell-shaped flowers, 0.5 to 0.75 inches across, are set singly in the axils of rounded green leaves that clasp the erect, slender, unbranched stems.  Inconspicuous at 6 to 18 inches high, this species is differentiated from five other Triodanis species found in Texas by its almost circular, toothed, clasping leaves.

Pink Stonecrop, also called Widow's Cross

Pink Stonecrop or Limestone Stonecrop (Sedum pulchellum), is a low-growing, apparently rare annual found on rocky ground in full sun, often among cactus and other Sedum species. Smooth, stem-clasping, cylindrical pale to lime green leaves (often with a reddish tinge), to 1 inch long, are densely arranged along the ascending to spreading stems.  These stems are topped with horizontally branched inflorescences that bloom from March to May, with numerous 4-petaled, pale pink flowers, to 0.5 inches across.  The petals are arranged in a cross-like pattern, giving rise to its other common name of Widow’s Cross. The Travis County population of this species, most often found on hilltops in the Bull Creek watershed, is disjunct by over 150 miles from other more eastern and northern populations, and likely represents the southwestern limit of its native distribution.

Heller's Plantain

Highly overlooked but quite common is Heller’s Plantain or Cedar Plantain (Plantago helleri), an erect annual that grows only in Central to West Texas and in southern New Mexico, typically in shallow, stony soils and on limestone bedrock exposures. From March through May, this species displays unusual, slightly overlapping flowers clustered at the top part of each stalk.  The flowers are quite small at 0.25-inches wide, with 4 off-white, nearly translucent petals that have a dark red center.  The stalks, to 10-inches high, arise from narrow, linear, basal leaves, to 8-inches long, and both stalks and leaves are softly hairy.  This species is can be commonly found along gravelly roadsides, and it is one of the host plants for the beautiful Common Buckeye butterfly.

Common Buckeye

Each spring, remember to look beyond the bluebonnets, paintbrushes, firewheels, and Mexican hats and take a closer look, because you just might be rewarded with one of these beguiling little bloomers!