The Rare White Bladderpod
The white bladderpod was registered in 1987 as a federally endangered species.
The Center for Plant Conservation (CPC) preserves rare, native American plants in a centralized network of 38 botanical gardens within 17 states and the Virgin Islands. In Texas, Mercer Arboretum & Botanic Gardens, San Antonio Botanic Gardens, and The Lady Bird Johnson Wildflower Center share the responsibility for the preservation of rare plants within seed banks or as live specimens. In addition, the CPC institutions, The Arboretum at Flagstaff, and the Desert Botanical Garden of Arizona maintain the rare mountain and desert species for Texas. In order to preserve the nation’s rare botanical treasures, Mercer and other CPC member institutions hold partnerships with concerned citizens, private and government conservation organizations, universities, and colleges.
Mercer maintains White Bladderpod (Physaria pallida) formerly known as Lesquerella pallida, a dainty, winter annual wildflower for the CPC’s National Collection of Endangered Plants. White Bladderpod plants reach a maximum height of two feet with gray to yellow-green foliage. The Latin word “pallidus,” meaning pale, describes the less than one-inch-wide white flowers the plant bears in the spring. Each flower has a yellow eye and produces a ¼-inch pea, or “bladder-shaped” fruit in late spring to early summer.
Dr. M. C. Leavenworth discovered Physaria pallida on small prairies near San Augustine, Texas in the 1830s. The rare plant only occurs in the wild in San Augustine County, Texas, and grows on open, rocky outcrops of unusual geological regions called Weches formations. Weches formations are bands of ancient marine sediments that lie parallel to the Gulf Coast from Sabine to Frio Counties. In East Texas, these alkaline “islands” of soil contrast the surrounding acid soils of the Pineywoods. The thin top layer of these alkaline sediments contains fossilized calcium-containing marine shells and covers a layer of clay. In San Augustine County, this clay traps water and remains saturated during rainy periods. The clay then becomes very dry during the heat of the summer. The seeds of Physaria pallida normally germinate in the Weches clay after fall rains and the plants overwinter as small tap-rooted plantlets.
Because the White Bladderpod is isolated within this very unique habitat, it is vulnerable to development, mining and is threatened by competition from other plants. Prior to development, periodic natural fires would reduce competition from other plants.
The White Bladderpod’s cousin, Zapata Bladderpod (Physaria thamnophila), is another very rare Texas native and occurs only in Zapata and Starr counties in West Texas and Tamaulipas, Mexico. In addition, four other uncommon kinds of Physaria occur in Texas.
The White Bladderpod is a member of the large family of plants named the Brassicaceae Family. Over 4,000 members of this family occur worldwide and are often referred to as the Mustard or Cabbage Family. The cross-like arrangement of the four petals found on the flowers of the Mustard Family inspired the former botanical name, the Cruciferae Family. The family is also characterized as bearing two-chambered fruits called capsules or siliques.
Sixteen other rare wildflowers in the family Brassicaceae remain on the Texas rare plant watch list and include: Cardimine macrocarpa, Draba standleyi, Leavenworthia texana, Rorippa ramosa, two kinds of Selenia, Sibara grisea, six kinds of Streptanthus, Thelypodiopsis shinnersii, and two kinds of Thelypodium. Leavenworthia texana, Texas Golden Glade Cress, shares habitat with White Bladderpod in San Augustine County, and also occurs in Sabine and Nacogdoches Counties. Like the White Bladderpod, Texas Golden Glade Cress and six other rare members of the Brassicacea listed above, are “endemic” to Texas, that is, these unique plants only occur in Texas. These wildflowers are important in that they provide nectar, forage, and seed for butterflies, birds, and other Texas wildlife. Mercer maintains seed of Texas Golden Glade Cress for the CPC’s National Collection of Endangered Plants, but this plant presently is not on display at Mercer. To view rare plants maintained by Mercer, visit
The Brassicaceae Family is also economically important as food crops: mustard, kale, brussels sprouts, broccoli, cabbage, cauliflower, and turnips (kinds of Brassica), horseradish (Armoracia), Japanese horseradish (Wasabia), radish (Raphanus), and watercress (Nasturtium) to name a few. In the 1960s, Canadian horticulturalists bred the nutritionally popular culinary oilseed crop, canola, from the Rapeseed plant, a member of Brassica group. Seeds of certain kinds of Physaria are currently under study as a source of fine oil for industrial and cosmetic use.
Many plants in the Mustard Family contain compounds that are irritating to animals eating them, and several Shepherd’s-purse (Capsella), Mustards (Brassica and Barbarea), and Peppergrass (Lepidium) often are considered weeds.
Approximately 90 kinds of Physaria occur in North America and Greenland. The yellow-flowered Alpine Bladderpod (P. alpina), a native of the Rocky Mountains, is grown in rock gardens of cool climates. The common Texas native, Big-flower Bladderpod (P. grandiflora) also bears yellow blooms and is used in sunny flower borders on well-drained soils. Other popular garden members of the Brassicaceae family include ornamental Cabbage and Kale (Brassica), Sweet Alyssum (Lobularia), Nasturtium (Tropaeolum), Honesty (Lunaria), Wallflower (Erysimum), Basket-of-gold (Aurinia), Stock (Matthiola), Rocket (Hesperis), Candytuft (Iberis), and Rock Cress (Arabis).
Stop by Mercer’s Endangered Species Garden from January until May to see the White Bladderpod covered with snow-white flowers and again in late spring and summer when they are covered with bladderpods.
In 1999, Dr. and Mrs. Sellers J. Thomas, Jr.; Mr. Frank A. Liddel, Jr.; Dr. and Mrs. Charles F. Squire of Houston; and the U.S. Fish & Wildlife Service generously sponsored the White Bladderpod for the CPC. The White Bladderpod benefits from annual sponsorship stipends directed to Mercer for equipment and supplies for the plant’s recovery.
Anita A. Tiller, Botanist
Mercer Arboretum & Botanic Gardens
Adapted from Parkscape,
Photos by Suzzanne Chapman
Updated February 28, 2012
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