Walden West ~ A hidden vernal pool

Thanks to the unexpected loss of transportation I’ve written of elsewhere, my June visit to the spot I call Walden West was significantly delayed. Arriving nearly at the month’s end, I found oppressive heat, swarming mosquitos, biting flies, and a dearth of blooms: a combination that quickly enough persuaded me to shorten my visit. Instead, I returned twice in July, combining June and July’s offerings into a single entry.

Over time, I’ve come to recognize the ‘pond’ at Walden West as a vernal pool: a small wetland with a seasonal cycle of flooding and drying. Some vernal pools flood in spring, due to melting snow, rain, or high groundwater, before drying by summer’s end. Others fill with rain in autumn, hold water through winter and spring, and then dry by late summer. In either case, the cycle of filling and drying makes them unique among wetlands, and plays a key role in determining which creatures can be found there.

By the end of June, heat and lack of rain had dried Walden West, leaving its depression filled with the dark, matted leaves typical of vernal pools. That said, some moisture remained, encouraging new growth. Mature hackberry trees in the area provided seed for their next generation. As for the shrub known as Groundsel Tree (or Eastern Baccharis), its fluffy white seeds can travel some distance; the seedling I found could have arrived from anywhere in the general neighborhood.

Hackberry seedling ~ possibly Celtis laevigata

Groundsel tree ~ Baccharis halimifolia

Despite the lack of surface water, dragonflies were everywhere: no doubt drawn to the area by those bothersome mosquitoes. This female Four-spotted Pennant (Brachymesia gravida ) had perched in what’s known as the obelisk posture: a handstand-like position created by raising the abdomen until its tip points at the sun. With the surface area exposed to solar radiation minimized, overheating is less likely.

Another common dragonfly, this female Eastern Pondhawk (Erythemis simplicicollis) paused from hunting to show off her beautiful colors atop a plantain stem.

A few damselflies flitted near the ground. One tiny, inch-long creature may have been an Eastern Forktail ((Ischnura verticalis) given its splendid green eyes, the pigmented area on the back of its eye (called an ‘eyespot’), and the solid green stripe along its thorax.

Fragile Forktails (Ischnura posita) are similar, although the male’s black thorax is marked with broken green shoulder stripes that resemble exclamation marks. Whatever the species, this was the smallest damselfly I’d ever encountered. Both Fragile and Eastern Forktails can be found in a wide variety of wetlands, including vernal pools.

Forktail damselfly (Ischnura spp.)

For insects seeking pollen or nectar, drought-tolerant choices were available. Hundreds — perhaps even thousands — of brilliant red Turk’s Caps (Malvaviscus arboreus var. drummondii) filled the woods. These shade-loving plants bloom from May until November; their small, edible apple-like fruits develop in tandem with newly-formed flowers. Turk’s Caps bloom most abundantly during summer heat, so July was a perfect time to find them.

The plant’s scientific name honors Scottish naturalist Thomas Drummond, who spent about two years collecting plants in the region of the Colorado, Guadalupe, and Brazoria Rivers. Since Walden West lies in Brazoria County, Drummond might well have seen the Turk’s Caps as he passed through.

His name also has been attached to about a dozen plant species, the moss genus Drummondia, and one mammal: the wood-rat Neotoma cinerea drummondii.

Unlike most members of the mallow family, Turk’s Cap flowers never fully unfurl. Instead, as the stigma develops, it extends above the petals: an open invitation to passing pollinators.

Another member of the Mallow family, the hisbiscus-like Salt-marsh Mallow (Kosteletzkya virginica) was equally abundant along the roads leading to Walden West.

A sun-lover, it doesn’t find the area around the pond especially congenial, but this single flower had found a bright spot in which to bloom.

Yet another mallow already was past its prime. The structurally attractive seed heads of the Swamp Rose Mallow (Hibiscus moscheutos) were scattered about, but I had to turn to my archives to find an image of one blooming at the edge of a creek that runs through the refuge. At times, their flowers are pink rather than white; I’ve seen only one plant with pink blooms, and that was in east Texas.

Swamp Rose Mallow seed head

Swamp Rose Mallow Flower ~ Hibiscus moscheutos

Other signs of a turning season were visible, including this nearly-dried stem of Virginia Wildrye (Elymus virginicus)…

and a few remaining fruits on dwarf palmettos. In time, the fully-ripened fruits will blacken, but eager creatures already seem to have been nibbling away.

Dwarf palmetto fruits

While there may have been Monarch butterflies in the neighborhood, I saw only Queens and Viceroys. Queen butterflies can be identified by the white spots on their wings; Viceroys have a dark, horizontal line paralleling their wings’ edge.

Queen butterfly on a late season Greenthread

Queen butterfly on Mexican Hat

Viceroy butterfly just hanging out on a branch

On this trip, huge spider webs decorated the woods, crossing every trail and opening; most seemed to have been spun by the Golden Silk Orb-weaver (Trichonephila clavipes ). One of our largest spiders, it’s easily recognized by its size, the colorful patterns on its body, and the fuzzy ‘gaiters’ on its legs that remind me of the baggywrinkle used on sailing vessels.

A special treat was finding this very small example of a favorite spider: a Green Lynx (Peucetia viridans) less than an inch long.

Larger green lynx and crab spiders were lurking among some familiar flowers, although none was inclined toward a photography session. No matter. The flowers themselves provided attractive bits of color, and a foretaste of autumn’s typical golds and purples.

Spotflower ~ Acmella repens

Wild Petunia ~ Ruellia nudiflora

Arrowleaf Sida ~ Sida rhombifolia

Looseflower Water Willow ~ Justicia lanceolata

It took some time to identify the Water Willow — at least provisionally. As so often happens, location helped. Justicia ovata, which has similar leaves and flowers and carries the same common name, isn’t found in Texas, and J. americana isn’t found along the coast. When I return to Walden West, I’m hoping to find more easily photographed flowers in order to confirm their identity.

A last mid-summer mystery was this plant, which at first glance I took to be alligator weed: a common invasive introduced into this country in 1894. In fact, I had found a different non-native: Indian Heliotrope (Heliotropium indicum). Several other Heliotropium species are native to Texas, including Salt Heliotrope (H. curassavicum), but obvious differences in the leaves made clear which I had found.

Like the sunflower genus Helianthus, heliotropes were named for the belief that the plants turned their rows of flowers to the sun as the day progressed: in Greek, helios means ‘sun’ and tropein, the source of ‘tropium,’ means ‘to turn.’ This heliotrope certainly turned my head; perhaps I’ll find a native version when I return to Walden West.

 

And so the seasons went rolling on into summer,
as one rambles into higher and higher grass.

Walden ~ Henry David Thoreau

Comments always are welcome.