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In this guide, biologist Mark Gustafson introduces residents and visitors to the history, geology, water resources, plants, and animals found in the nineteen counties occupying the eastern part of the Edwards Plateau, the heart of the Hill Country. He profiles three hundred of the most common and unique species from all of the major groups of plants and animals: trees, shrubs, wildflowers, cacti, vines, grasses, ferns, fungi, lichens, birds, mammals, reptiles, amphibians, fishes, and invertebrates. Color photographs are included for each species along with a brief description. He closes with a chapter on significant state parks and natural areas in the region as an invitation to visit and explore the Texas Hill Country. As large metropolitan areas continue to encroach on the Hill Country, newcomers are moving in and more people are flocking to its many attractions. This guidebook will enrich the appreciation of the region’s rich and unique biodiversity and encourage conservation of the natural world encountered.
About the Author
MARK GUSTAFSON is professor of biology at Texas Lutheran University in Seguin, Texas, where he directs the environmental studies program and specializes in aquatic biology and ecology.
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A Naturalist's Guide to the Texas Hill Country
By Mark Gustafson
Texas A&M University PressCopyright © 2015 Mark P. Gustafson
All rights reserved.
Trees and Shrubs
TREES AND SHRUBS PROVIDE the framework for the ecological communities of the Hill Country. The distribution of other species is often strongly related to tree distribution. For example, the endangered Golden-cheeked Warbler is dependent on Ashe juniper for its nesting materials and thus will not be found nesting in areas lacking this tree. Trees and shrubs often provide large amounts of food for animals in the form of fruits and nuts. The leaves and wood are seldom important food sources because they usually contain chemicals that are toxic to animals or that make it difficult for the plant material to be digested. New growth on the ends of branches is an exception and is often browsed by deer and other animals.
Much of the land in the Hill Country is dominated by Ashe juniper and live oak. However, there are dozens of other species that occur frequently to rarely. The species found here are an interesting mix typical of desert, forest, and plains regions. The described species are arranged alphabetically by scientific family name. Species in the same family are listed alphabetically by genus and species. Leaves, flowers, and fruit are all helpful in identifying specimens.
Woodland of Ashe juniper and Live oak at Garner State Park
Simple leaves, long and grass-like
Twist leaf yucca
Simple leaves, narrow
Retama (if leaflets have fallen off)
Simple leaves, oval and unlobed
Simple leaves, lobed
Texas mountain laurel
Acer grandidentatum Aceraceae Maple Family
Bigtooth maple is the star attraction in the fall at Lost Maples State Natural Area, where it is abundant along the Sabinal River. The leaves are about 3 inches wide and turn orange or red in November. It is also found in various other canyons in the Hill Country, as well as in the mountains of West Texas and several of the western states. How did the maples get "lost" in the Hill Country? Maples usually occur in areas with moister soil than most of that in present-day Central Texas. During the ice ages, the climate in Texas was much cooler and wetter; hence, it is likely that maples were more widely distributed at that time. As the climate became warmer and drier during the past 10,000 years, the only place that the maples could survive was in shady canyons along spring-fed streams, where there is a steady supply of groundwater.
Acer negundo Aceraceae Maple Family
Boxelder is in the same genus as the bigtooth maple but cannot be confused with it because the leaves of boxelder are compound. Usually they have three or five leaflets, but they can have up to nine. The leaves are very similar to those of poison ivy, and poison ivy can appear to come from a trunk when it is growing along the branches of a tree. The leaves of poison ivy are alternate, whereas those of boxelder are opposite. In the fall, the paired, winged seeds easily identify it as a maple. Boxelder occurs widely in North America and Central America.
Rhus aromatica Anacardiaceae Sumac Family
This sumac has three leaflets per leaf, the leaves are alternate, and they are deciduous. It has small yellow flowers in the spring and red fruit in clusters starting in June. The branches and leaves have a distinct odor when broken. Skunkbush is native to the western half of the United States.
Rhus virens Anacardiaceae Sumac Family
This shrub has evergreen, alternate, compound leaves with five to nine leaflets. The leaflets are dark green and shiny, do not have teeth, and are retained in the winter. The small white flowers grow in clusters, and the fruits are red and hairy. Evergreen sumac flowers in the summer after rains, and fruits are produced in the fall. It occurs on rocky hillsides from Central Texas west to New Mexico and Mexico.
Sabal minor Arecaceae Palm Family
This is one of two native species of palms in Texas. The leaves are fan shaped as in most palms and grow from a subterranean stem. Dwarf palmetto grows as a shrub along some of the Hill Country streams, as well as many wet areas throughout East Texas and the southeastern United States. The Hill Country populations are probably relicts from a broader distribution during the ice ages. The other native palm in Texas is a tree (S. mexicana) and occurs naturally only in the Rio Grande Valley and southward into Central America. Dwarf palmetto is common along the creek at Honey Creek State Natural Area in Comal County.
Dasylirion texanum Asparagaceae Asparagus Family
Texas sotol is common on rocky hillsides of the Hill Country. Two other species of sotol occur in West Texas. The long, thin leaves have curved spines along the edges. The flowers are located on a thick stalk that can be more than 10 feet tall. Native Americans used the bulb at the base of the leaves to make flour. Sotol has been widely adopted as an attractive landscape plant that never needs supplemental water.
Nolina texana and N. lindheimeriana Asparagaceae Asparagus Family
Beargrass looks like a clump of tall grass, but the leaves are green year-round, and in the spring the plant produces flowering stalks with small white flowers. Nolina texana has narrow leaves with smooth margins (or widely spaced teeth). Nolina lindheimeriana has sawtoothed leaf margins (another common name is devil's shoestring), and it forms much thinner clumps than N. texana.
Yucca constricta Asparagaceae Asparagus Family
This yucca can be recognized by the almost perfectly globe-shaped cluster of leaves. The leaves are about 1/2 inch wide and up to 2 feet long. The margins have long threads that curl off. The pale flowers are produced on a stalk that extends several feet above the leaves. This species is found only in Texas. Yuccas are pollinated by a specific group of moths called yucca moths. Yuccas also can reproduce vegetatively, sprouting new plants from the base.
Twist Leaf Yucca
Yucca rupicola Asparagaceae Asparagus Family
Twist leaf yucca is endemic to the Texas Hill Country and is very common in many parts of the region. The twisted leaves easily distinguish it from other yucca species. It is also usually much smaller than the other common yuccas of the Hill Country and does not form a trunk. Twist leaf yuccas produce a stalk with white flowers in the spring.
Yucca treculeana Asparagaceae Asparagus Family
This yucca has broad, spearlike leaves, 1–3 inches wide and up to 3 feet long. The woody stem can grow 10 feet tall. The dead leaves bend back on the stem below the crown of leaves. The white flowers are produced on a stalk just above the leaves in March and April. It occurs from the southern part of the Hill Country through South Texas and northern Mexico.
Poverty Bush, Roosevelt Weed
Baccharis neglecta Asteraceae Aster Family
This tall shrub is most often found in disturbed areas such as neglected fields and in dry riverbeds. It has narrow green leaves that are about 1.0–2.5 inches long. In the fall the female plants produce attractive silky plumes on the flowers. It occurs throughout Texas and into Mexico. Poverty bush produces large numbers of seeds and can resprout or grow from seed after fires or cutting.
Berberis trifoliolata Berberidaceae Barberry Family
Agarita is one of the most common shrubs in the Hill Country, often forming an impenetrable ring around the base of large trees. It is easily recognized by its three leaflets, each of which has several very sharp points. The early-spring flowers are small and yellow and attract a wide variety of insects. The berries are bright red and can be used to make jelly. The bright yellow root has been used as a dye. A close relative, Texas barberry (B. swaseyi), is endemic to the Texas Hill Country but is much less common than agarita. It is very similar to agarita but has five to nine leaflets per leaf.
Celtis laevigata Cannabaceae Hemp Family
Netleaf hackberry is native to the western United States, and sugar hackberry is native to the southeastern United States. Their ranges overlap in the Hill Country. Both species have simple leaves that come to a point. The leaves of netleaf hackberry are rough on the upper surface, while those of sugar hackberry are smooth and the shape is narrower. Both species have small round fruits about 1/4 inch in diameter. Both species often have wartlike growths on the bark and are frequently parasitized by mistletoe. Hackberry trees are fast growers and common in urban areas even though they are seldom planted. The berries are an important food source for birds and mammals, and the leaves are often consumed by insects.
Juniperus ashei Cupressaceae Cypress Family
Ashe juniper, also known as mountain cedar, is a dominant tree in the Hill Country. It covers the majority of hillsides and upland areas. Dense stands are called cedar brakes. This tree is easily recognized by its small, scaly leaves. Male trees produce huge amounts of pollen in the winter months, leading to "cedar fever" in those people who are allergic to the pollen. Female trees produce blue cones that look like berries in the summer and fall. Ashe juniper is native to the Hill Country but has greatly increased in abundance due to the reduction in wildfires. The endangered Golden-cheeked Warbler uses the bark from large Ashe juniper trees to build its nests. The berries of Ashe juniper are an important food source for birds and small mammals.
Taxodium distichum Cupressaceae Cypress Family
Much of the beauty of Hill Country rivers can be attributed to the huge bald cypress trees that line their banks. Currently, the state's largest bald cypress, which has a circumference of 37 feet and is 94 feet tall, is located in Real County in the western part of the Hill Country. Bald cypress is a deciduous conifer with leaves that turn rusty-red in the fall. The green balls at the ends of branches are the female cones. Bald cypress often have "knees," or projections from the roots. However, not all bald cypress trees have knees, especially those along Hill Country rivers, and their function is not yet clear to scientists. The wood of bald cypress is very strong and rot resistant, and many of the huge trees that once lined the rivers of the Hill Country were cut down by early settlers for lumber. The Hill Country is the western edge of the range of bald cypress, which occurs throughout the southeastern United States.
Diospyros texana Ebenaceae Ebony Family
This is one of the most common shrubs and small trees in the Hill Country. A distinctive feature is that the edges of the leaves roll under. The gray bark is smooth and peels off as the trunk and branches grow. The fruits, which occur only on female trees, start out green and turn black when they are ripe. They are edible but contain several large seeds that make them less palatable to humans. The wood of persimmon is extremely hard and dense.
Arbutus xalapensis Ericaceae Heath Family
Texas madrone is a beautiful small tree with reddish or pink bark that peels off. The leaves are dark green and leathery, the flowers are white, and the fruits are red. This tree is in the same family as blueberries. Texas madrone is fairly uncommon in the Hill Country but also occurs in the mountains of West Texas and south to Guatemala. Small madrone plants are readily eaten by browsers such as deer, which may play a role in the rarity of the tree in the Hill Country.
Sapium sebiferum Euphorbiaceae Spurge Family
Chinese tallow is a nonnative invasive tree that is spreading in the Hill Country. Its leaves look somewhat like those of the native cottonwood but have smooth rather than scalloped margins. The leaves turn red or yellow in the fall. Chinese tallow can spread quickly because of its rapid growth, abundant seeds, and production of suckers (sprouts from the stem or roots). Dense forests of these trees can exclude native species, and their leaf litter in water has been shown to affect tadpole survival. They have become especially abundant on the Gulf coastal plain, where they have spread into native prairies.
Texas Mountain Laurel
Dermatophyllum secundiflorum Fabaceae Legume Family
This common shrub is known for its beautiful purple clusters of flowers that smell like grape Kool-Aid. It is widely used in landscaping throughout Central Texas because of its beauty and drought tolerance. However, it is rather slow growing. The evergreen leaves are compound with 5–14 leaflets. The pods contain hard red seeds, which are toxic to both humans and animals.
Eysenhardtia texana Fabaceae Legume Family
The compound leaves of Texas kidneywood are about 3 inches long and have up to 40 leaflets. Crushing the leaves results in a strong odor. The flowers are white and arranged in a spike and are visited by many species of insects. The shrubs have many branches and lack thorns. Deer like to browse this species. It lives in the southern half of Texas and in Mexico.
Parkinsonia aculeata Fabaceae Legume Family
Retama is a tropical species that reaches its northern limit in Central Texas. It has distinctive long leaves with tiny leaflets, which are often shed from the grasslike leaf stalk. The bark is green, and the branches have sharp spines. The yellow flowers are produced in the summer and are followed by pods 2–4 inches long. It usually grows in open, disturbed areas such as pastures or dry streambeds.
Prosopis glandulosa Fabaceae Legume Family
The leaves of mesquite have two main leaflets, each of which has many pairs of narrow subleaflets. The tree has an open, airy appearance. The trunks almost always grow at an angle from the ground, and mesquites frequently resprout from the base. Spines are common on the branches at nodes. The flowers are yellow and found in 2-inch spikes at the ends of branches. The pods are slender and green or brown. The dense wood is favored for cooking barbecue and is also used for making furniture. Native Americans and European settlers used mesquite in dozens of other ways as well.
Sesbania drummondii Fabaceae Legume Family
Rattlebox is a tall shrub found in open, wet areas such as along streams or ponds. The leaves are compound with about 40 leaflets per leaf. The yellow flowers hang in clusters. The fruits are a distinctive pod that has four wings along the sides. When dry, the seeds rattle in the pod. The seeds are poisonous to livestock and humans.
Texas Red Oak, Spanish Oak
Quercus buckleyi Fagaceae Beech Family
Texas red oak leaves are deeply lobed with long points at the ends. The leaves turn red in the fall. The acorns of these and other oaks are an important food source for mammals. Texas red oaks are common small- to medium-sized trees in the Hill Country on limestone hillsides. Many of the oak species are susceptible to the fungus that causes oak wilt, which has been killing oak trees throughout Texas and other states. Recent evidence suggests that this fungus was introduced to the United States. Information on protecting oaks from this disease is available on the website of the Texas Forest Service.
Texas Live Oak, Plateau Live Oak
Quercus fusiformis (Q. virginiana var. fusiformis) Fagaceae Beech Family
Live oaks are abundant throughout the Hill Country. The leaves of Texas live oak are usually not lobed and are about 1–3 inches long. Small trees commonly sprout from the roots of large trees, and these sprouts usually have hollylike leaves with pointed lobes. This species is sometimes considered a variety of the southern live oak (Q. virginiana), which grows farther east, due to hybridization in Central Texas. Live oaks can be infected by a fungal disease called oak wilt (see red oak). Live oaks commonly have round pinkish or brown galls on them, caused by the mealy oak gall wasp.
Quercus laceyi Fagaceae Beech Family
This medium-sized oak tree is characterized by leaves that are shallowly lobed (similar to live oak leaves) but have a waxy coating and blue-green color. This uncommon species is found only on the Edwards Plateau and in northeastern Mexico. It grows on rocky limestone hillsides.
Quercus marilandica Fagaceae Beech Family
Blackjack oak leaves have pointed tips at the ends of three large lobes. The leaves are not deeply lobed like those of Texas red oak. The trees are fairly small, growing to only about 30–40 feet tall. In the Hill Country, they usually grow in dry, sandy soil such as in the Llano Uplift area. This species occurs throughout the southeastern United States and reaches the western edge of its range in the Hill Country.
Excerpted from A Naturalist's Guide to the Texas Hill Country by Mark Gustafson. Copyright © 2015 Mark P. Gustafson. Excerpted by permission of Texas A&M University Press.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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Table of Contents
Geology of the Hill Country,
Water in the Hill Country,
Human History and Influence on the Land,
1. Trees and Shrubs,
3. Cacti, Vines, Grasses, Ferns, and Other Plants,
4. Fungi and Lichens,
11. State Parks and Other Natural Areas,
Austin, San Antonio