Plant Loop Trail
Desert Tortoise Research Natural Area Virtual Field Trip
Plant Loop Trail
There are over 160 species of perennial and annual flowering plants in the Desert Tortoise Research Natural Area. Many of these plants provide food and shelter for the desert tortoise and the other animals that live here. Xeric adapted plants have evolved many strategies to deal with the harsh realities of life in the desert. The plants selected here illustrate some of these adaptations.
POST #1 Creosote Bush, Larrea Tridentata
The long-lived creosote bush, Larrea tridentata, displays many adaptations for moisture conservation:
- its small leaves are covered by a wax that inhibits moisture loss;
- the leaflets fold together to decrease surface area which also decreases water loss;
- during extremely dry times the leaves are shed to further conserve moisture.
The creosote bush goes through several forms during its life. It begins as a single-stemmed plant and may live in this form for 50 to 200 years. Gradually, as the shrub ages, the center stem dies out, leaving dead branches in the center of the plant while the edges continue to grow outward. As the center dies it fills with sand. After hundreds (and thousands) of years, the edges of the growing plant will form a ring of small creosote bushes with a radius of several meters. From estimates of the rate the radius of rings increases, scientists are able to age creosote rings. Many are thought to be thousands of years old, with the oldest being over 11,000 years in age! The round, leafy balls the size of walnuts on the stems of creosote bushes are caused by a small insect known as the creosote gall midge, Asphondylia aurinila.
The creosote ball midge is a small gnat-like insect. Recent galls often appear green and those from past years are brown. The long-lived creosote bush, Larrea tridentata, displays many adaptations for moisture conservation.
POST #2 Spiny Hop-Sage, Grayia spinosa
The distinctive gray-tipped leaves and striated bark make the spiny hop-sage, Grayia spinosa readily distinguishable from other shrubs with which it is associated.The hop-sage is dioecious, meaning that male and female flowers are found on separate plants. The female plant displays bright purplish bracts (flat fruits) in the spring, that make this one of the showiest shrubs in the Mojave desert.The hop-sage shown here is a female plant that grows close to the Desert Tortoise Research Natural Area’s Interpretive Center. Note the swathes of gold-fields carpeting the background.
POST #3 Mojave Aster, Xylorhiza Tortifolia
The Mojave aster (Xylorhiza tortifolia) is widespread on southern deserts, largely in creosote scrub community. The flower of this hardy desert perennial can vary from violet to lavender or almost white.The usual habitat for this species is rocky slopes, but it can be seen occasionally in dry, flat areas such as here at the Desert Tortoise Research Natural Area.In April and May a Mojave aster may produce as many as 20 blooms, making it very attractive and obvious. After bloom, the plant dies back leaving inconspicuous barren stems and brown leaves.
POST #4 Paperbag Bush Salazaria Mexicana
The inflated seed pods of the paperbag bush Salazaria mexicana begin as the calyx (the outer leaves that surround an unopened flower bud). As the purple and white pea-like flower dries and disintegrates, the calyx enlarges to become a papery sack about a half an inch in length, sometimes tinged pink. As a water conservation adaptation this shrubby member of the mint family has very small leaves and loses most of them during the drought of the summer.
POST #5 Spring Color
POST #6 Annuals
Germination of annual wildflowers occurs only when moisture is abundant enough to ensure the plants time to flower and produce seeds. At the DTRNA, most annual wildflowers germinate after the winter rains and bloom during the spring months providing food for tortoises and other wildlife when they emerge from hibernation. Here a desert tortoise can be seen wandering through a sea of goldfields, Lasthenia californica.
POST #7 Dried Annuals and Grasses
Tortoises eat dried annual plants and grasses from late spring through early fall. This is split grass, Stipa speciosa.
POST #8 Lichens
A lichen is two different organisms, an alga and a fungus, living together as a single unit in a symbiotic relationship. The alga provides food through photosynthesis and the fungus forms a support matrix and supplies the necessary water. Dry forage forms most of the tortoises’ diet when live plants are no longer available. They eat the dried stems, leaves, flowers, and fruits of plants such as split grass, blazing star, gilias, desert dandelion, filaree and many other species. Lichens are extremely resilient and able to withstand the wide extremes in temperature found in the desert. This attractively colored lichen is growing on a rock. Lichens have four growth forms. This is a crustose form — growing as a tight crust on the rock surface.
POST #9 Joshua Tree, Yucca Brevifolia
Joshua trees, Yucca brevifolia, can be found in the most elevated areas of the Desert Tortoise Research Natural Area. These magnificent but incredibly slow-growing members of the lily family occur throughout the Mojave desert. Indeed, the presence of Joshua trees is a useful indicator that an area is part of the Mojave desert biome. Joshua trees may reach a height of 30-35 feet.
POST #10 Beavertail Cactus, Opuntia Basilaris
The beavertail cactus is a low growing member of the prickly pear family. The flat stems or “pads” lack the large spines found in the closely related cholla but are covered with dense tufts of glochidia — tiny, needle-sharp, barbed “hairs” that are very irritating to the skin and very difficult to remove. Despite the glochidia, desert tortoises do eat the pads.The spectacular spring magenta flowers give way to small seed-laden fruits. Beavertail cactus is found at the Desert Tortoise Research Natural Area mainly at the higher elevations.
POST #11 Winter Fat, Krascheninnikovia Lanata
Winter fat (Krascheninnikovia lanata) can be identified even from a distance by the white, hairy seeds that tip the branches of the plant. It is a member of the lamb’s quarter family (Chenopodiaceae) and is related to the spiny hop-sage.
- is valued as a winter grazing plant by ranchers throughout the western US.
- Indians made a tea from the plant to drink and to wash hair.
- The Zunis chewed the fresh root and used them as a burn remedy.
- Birds collect the soft hairy seed to line their nests.
Photo credits: Kristin H. Berry, Robert D. Berry, Nathan W. Cohen, Michael J. Connor,
Ralph Crane, Susan Moore, Mary H. Shepherd, Beverly Steveson, Laura Stockton