Monday, April 25, 2011

Spring Wildflowers

First, a warning: the evil has leafed.  The evil is Poison Ivy (Toxicodendron radicans), enemy of hikers, campers, dog owners, and backyard brush clearers.  Poison Ivy thrives anywhere there is an ecological edge which, in this vastly human-disturbed landscape, is just about everywhere – along roads, along creeks, along trails, along fences, at the edge of the woods, at the edge of the lawn, or at the edge of a clearing.  In other words, it grows just about everywhere you might go looking for wildflowers.

Poison Ivy always has trifoliate leaves, or leaves composed of three leaflets.  The terminal leaflet is symmetrical and has a longer petiole (leaf stem) than the side leaflets, which tend to be slightly asymmetric, with deeper notches on the bottom side of the leaf.  The overall size of the leaves, and how deeply lobed or notched the leaflets are, varies greatly, as does the overall habit of the plant.  Poison Ivy grows as a shrub, ranging in size from a single twig to a thicket in the forest understory, or as a vine that climbs up the trunks of trees or the sides of rocks.  The most successful Poison Ivy plants that I have seen are in east Austin, along Boggy Creek, where they have attained "tree" status.  At first glance, a tree grows along the creek, but on closer inspection, the "tree" is actually a massive explosion of lush Poison Ivy vines being supported by the trunk of a long-dead tree.  Think Medusa's hair, the plant version. 

In the spring, when the trees are leafing and the wildflowers are blooming, the leaves of Poison Ivy are shiny green and especially appealing, but be forewarned that the shininess of the leaves is in part due to the oils that the plant produces, which contain urushiol, a compound that causes mild to extreme skin irritation in most people.  Hence the "poison" part of the name.  The best defense against Poison Ivy is to learn to identify its leaves and to avoid them.  And, despite the variability of the plant, knowing it, as in being able to spot a single leaf in a forest, is quite possible because the plant has a very strong presence.  Even in winter, its twigs have a certain curl to them, and its hairy, older vines hum with warning, seeming to simultaneously draw attention while saying, Stay away from me.  So, learn its leaves, because they literally are everywhere, even leaping, looking friendly and pretty and all spring green, across the well-used Homestead Trail at McKinney Falls.

Poison Ivy (Toxicodendron radicans) leaping into the trail

It's been a couple of weeks since Lee and I hiked the Homestead Trail – a couple of long, hot, rainless weeks for April – so, while I thought I was capturing the start of the wildflower season, I was actually lucky to capture a variety of wildflowers in their short moment this spring, before the especially-early summer began.  One of the first flowers that I spotted along the trail was Blue-Eyed Grass, a perennial herb that blooms only in the spring.  Many varieties of Blue-Eyed Grass (Sisyrinchium spp.), which is related to the iris flower, grow in open woods and grassy areas throughout central Texas.  It is difficult to distinguish between species because they hybridize with each other, producing many variants.

Blue-Eyed Grass (Sisyrinchium sp.)

Blue flowers, more of a rarity in the yellow-dominated fall, are well represented among the spring wildflowers.  Baby Blue Eyes (Nemophilia phacelioides) is a blue-flowered spring ephemeral, meaning that it blooms briefly in the spring and disappears by summer.  Like other spring ephemerals, such as Missouri Violet, Baby Blue Eyes grows in moist, shady woodlands, where it does most of its quiet growing in the winter, after the leaves have fallen from the trees overhead, allowing more sunlight to reach the forest floor.  The plants bloom in the early spring, just before the trees leaf out and, in blooming, become visible to us, signaling that spring has arrived.  But just as quickly as they are visible, the spring ephemeral herbs die back under the leaf litter until next year, earning their ephemeral reputation.  The blue flowers of Baby Blue Eyes attract butterflies, moths, and bees during their brief bloom period in March and April.

Baby Blue Eyes (Nemophilia phacelioides)

Another spring-blooming blue flower is Giant Spiderwort, which is common throughout my east Austin neighborhood, where it blooms in shady spots and abandoned lots in March and early April.  Like many early bloomers, Giant Spiderwort (Tradescantia gigantea) is a perennial herb that emerges from its roots in the fall, grows up to three feet tall during the winter, blooms in early spring, and dies back in the hotter weeks of late spring.  The color of the flowers varies from deep blue, when the plant grows in acid soils, to purple, to pinkish purple, when the plant grows in alkaline soils.  Though I did see a few of the plants blooming along the Homestead Trail, this picture is from my backyard in east Austin, where Spiderwort blooms purple.

Giant Spiderwort (Tradescantia gigantea)

Among spring wildflowers, in contrast to fall wildflowers, there are also many monocots, including Blue-Eyed Grass and Spiderwort.  This is because many monocots, like irises, tulips, and crocuses, regrow from bulbs or corms in the soil, growing and blooming in the cooler, moister winter and spring, then dying back in the hotter summer.  Onions and garlic are examples of monocots in the Lily Family that grow from underground bulbs.  Wild Garlic (Allium drummondii) is native to Texas and the Plains states to the north, forming large colonies in fields, pastures, and other grassy areas.  Wild Garlic blooms March through May in flowers that range from white to purple-red.

Wild Garlic (Allium drummondii)

Another Lily Family plant that blooms in the spring is the Rain Lily, a striking white-flowered herb that also regrows yearly from an underground bulb.  The blooming of the Rain Lily (Cooperia pedunculata) is triggered by rainfall, so in years when we have ground-soaking rains in April and May, fields and open woodlands seem to sprout an abundance of the white flowers overnight.  In drier years, like this one, the Rain Lilies are fewer and are restricted to moister, shadier spots.

Rain Lily (Cooperia pedunculata)

Southern Dewberry is a common plant in our area, growing as thorny vine that forms thickets along fences and roadsides.  Its bloom period is brief though, in March and April, and, in that, it joins the ranks of the spring wildflowers.  Southern Dewberry (Rubus trivialis) has flowers characteristic of the Rose Family, with five non-fused petals, lots of stamens, and many carpels.  The flowers, if pollinated, develop into summer blackberries, which provide food for wildlife.

Southern Dewberry (Rubus trivialis)

Another common wildflower that begins blooming in spring and continues throughout the summer and into the fall, rainfall permitting, is Yellow Wood-Sorrel, a perennial herb that is a common garden and greenhouse weed throughout North America.  Yellow Wood-Sorrel (Oxalis stricta) has trifoliate leaves that resemble three-leafed clover leaves and five-petaled yellow flowers.

Yellow Wood-Sorrel (Oxalis stricta)

The Homestead Trail is mostly shaded as it winds through a woodland of Cedar Elm, Hackberry, Ashe Juniper, and Mesquite trees, but it also passes through more exposed areas.  On one such rocky hillside, I found a Two-Leaved Senna, a Prairie Larkspur, and Pink Mimosa flowering side by side amidst last fall's dead grasses.  Pink Mimosa is a shrub of rocky hillsides, canyons, and limestone soils that blooms in pink to white puffballs in the spring.  The leaves of Pink Mimosa (Mimosa borealis) are twice pinnately compound, meaning each leaflet is composed of many tiny sub-leaflets, giving the leaves a feathery appearance.  Puffy mimosa flowers provide nectar for bees and butterflies.

Pink Mimosa (Mimosa borealis)

Prairie Larkspur (Delphinium carolinianum), a spring wildflower that prefers sandy soils, also grows in open woods, fields, and roadsides.  Prairie Larkspur blooms from April to June and its flowers range in color from white to pale blue to blue violet.

Prairie Larkspur (Delphinium carolinianum)

Two-Leaved Senna (Senna roemeriana) is a perennial Pea Family shrub that grows in fields or dry, open hillsides with limestone soils.  Two-Leaved Senna gets its name from its leaves, each of which is a symmetric pair of leaflets resembling one, divided leaf.  From April through October, Two-Leaved Senna produces yellow, five-petaled flowers that attract birds and butterflies.  The shrub is a larval host to sulfur butterflies, and its seeds are an important food source for central Texas birds.

Two-Leaved Senna (Senna roemeriana)

At the northern end of the Homestead Trail, the trail passes by a Texas Parks Department building, which is surrounded by a field of wildflowers.  The mix of wildflowers in that field resembles the mix of colors along many of our major roadways, leading me to believe that, just as the highway department seeds the wildflowers along the right-of-way, the parks department probably seeded the Texas Bluebonnets, Indian Paintbrush, and Antelope Horns decorating the field behind its building.

Texas bluebonnet, state flower of Texas, is the classic spring wildflower.  Bluebonnets are winter annuals that germinate after the fall rains, grow as rosettes through the winter, and bloom in the spring.  Texas Bluebonnets (Lupinus texenis) have palmately-compound (fan-shaped) leaves and white-tipped, blue flower spikes.  Up close, the flowers are blue with white centers and resemble sweet pea flowers.  Within a flowering spike, some of the older flowers have maroon or purple centers instead of white centers; the maroon-centered flowers have already been pollinated and, lacking the white accent, are now less attractive to bees, butterflies, and other pollinators.  Texas Bluebonnets grow in abandoned fields and pastures and thrive in the alkaline, limestone soils of central Texas.  The seeds of bluebonnets have been spread throughout the state by the highway department, making the blue flowers common along major Texas roadways in the spring.

Texas Bluebonnets (Lupinus texenis)

Indian Paintbrush (Castilleja indivisa) was originally native to the Llano Uplift region of the Edwards Plateau, where it thrived in sandy soils.  Like the Texas Bluebonnet, however, the Indian Paintbrush has been distributed throughout the state by the highway department, so now it is common to see the bright red flowers of the Indian Paintbrush in the same pasture or roadside as the striking blues of the Texas Bluebonnet.  Indian Paintbrush is hemi-parasitic, or partly parasitic, in that it grows its roots into the roots of other plants, such as grasses, and steals their nutrients.  The flowers of the Indian Paintbrush attract butterflies, and the nectar of flowers is a food source for hummingbirds and insects.

Indian Paintbrush (Castilleja indivisa)

My current favorite spring wildflower looks to me more like an alien life form than a wildflower.  A member of the Milkweed Family, Antelope Horns (Asclepias asperula) is an important food source and larval host for monarch and queen butterflies.  Antelope Horns grows in open fields and along roadsides, thriving where the soil is rocky or sandy.  The large, round inflorescences of Antelope Horns appear otherworldly, improbably large and solid for such low-growing plants, but to many pollinators, including a bees, flies, butterflies, and birds, each globe of flowers offers a buffet of nectar in a otherwise hot and dry spring.

Antelope Horns (Asclepias asperula)

Along the trail, as it wound into and out of the woodlands, crossing and recrossing the mowed park road, I also saw some of the less famous, but just as steady and reliable, of the wildflowers that decorate our roadways in the spring.  Engelmann's Daisy is one such common roadside wildflower that grows in open fields and dry, upland soils.  Engelmann's Daisy (Engelmannia peristenia, formerly E. pinnatifida) can be distinguished from other yellow sunflowers by its spring blooming time and long leaves with deeply wavy borders.  A drought-tolerant perennial, Engelmann's Daisy is abundant and ecologically important in central Texas, providing nectar for insects, seeds for birds, and forage for livestock.

Engelmann's Daisy (Engelmannia peristenia)

Another roadside wildflower, the Evening Primrose, put on a good show this year, decorating roadsides throughout Austin in pink for most of late March and early April.  Pink Evening Primrose (Oenthera speciosa) is a perennial herb that spreads from rhizomes, or underground root runners, forming extensive colonies in fields and along roadsides.  Evening Primrose is drought tolerant and thrives in full sun, making it a reliable ground cover and wildflower even in dry years such as this one.  The flowers are distinctive, with long, four-branched stigmas and pink-white petals, and the seeds are food for native finches.

Pink Evening Primrose (Oenthera speciosa)

Prairie Verbena is a perennial herb that grows in open, grassy areas.  Prairie Verbena (Glandularia bipinnatifida) is very common throughout the state, where it blooms from spring through fall, rainfall permitting.  I've noticed that this month, as the heat and drought have progressed, Prairie Verbena has held its place along the roadsides as other spring-only wildflowers have faded.  Prairie Verbena has highly dissected leaves (or highly pinnatifid leaves, hence its Latin name) and nectar-rich flowers that attract birds and pollinating insects.

Prairie Verbena (Glandularia bipinnatifida)

After walking the Homestead Trail, we looped around from the Lower Falls to the Upper Falls then back to the parking lot along the shadier, rockier Rock Shelter Trail, where the red flowers of Cedar Sage decorated the ledges above Onion Creek.  Cedar Sage (Salvia roemeriana) is adapted to growing in the shade and leaf mulch of Ashe Juniper, known locally as Cedar trees, which is how this native sage got its name.  Cedar Sage grows on limestone ledges and rocky canyons throughout the Hill Country, attracting hummingbirds and butterflies with its flowers in spring and early summer.

Cedar Sage (Salvia roemeriana)

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