|Arbutus distribution map|
Madrone is the common name for all the species of trees under the genus Arbutus, which are mainly found along the Pacifc coastline of the United States and Mexico. The three main species are Arbutus arizonica, Arbutus menziesii, and Arbutus xalapensis. They are easily recognized because of their unique peeling bark that reveals a new, vibrant color of the tree. The Native Americans saw this tree as sacred and used it for medicinal purposes, they also believed that its roots held the Earth together because they ran so deep. Today, the population of Madrones is dwindling due to diseases as well as urbanization.
The anatomy of the genus Arbutus varies between the three main species; arizonica, xalapensis, and menziesii.
The arizonica, or common name Arizona Madrone, can either be considered to be an evergreen tree, or a shrub. It has stout branches that spread out from the trunk and form a round top called a crown. The Arizona Madrone is able to grow from 19 to 50 feet tall, and its diameter is normally 18 to 24 inches. The bark of the Arizona Madrone annually peels off in thin sheets, revealing a vibrant red or orange trunk. Its leaves are thick and rough, generally 2 to 3 inches long. New leaves are produced by the Arizona Madrone in May, these new leaves replace the old leaves and can last for the entire year. It flowers during the period in between April and June, and the berries ripen in the fall. The berries are small but sweet and contain many seeds.
The xalapensis, or common name Texas Madrone, is also considered to be either an evergreen tree, or a large shrub. The branches of the Texas Madrone are stout and spreading, but crooked and do not form a rounded crown. At a mature age, the tree can be 20 to 40 feet tall with a diameter slightly smaller than the Arizona Madrone. Similar to the Arizona Madrone, the Texas Madrone's bark peels off in thin, papery layers to reveal new, colorful bark. The new bark's color can be white, orange, pink, tan, or dark red. As the bark ages, it turns brown, gray, or black. The color of it's leaves is dark green, while the texture tends to be thick and leathery. 3 inch long white blossoms begin to form in the early spring, eventually producing berries that ripen in the fall. The berries are usually red or yellow and round with many bumps, only growing to around a quarter of an inch in diameter.
The menziesii, or common name Pacific Madrone, is an evergreen tree. It is the largest species of Madrones and is capable of growing 16 to 130 feet tall. It is a very thick tree with a diameter of 2 to 3 feet. Its trunks curve to from a broad, round crown, with twisting limbs. Like the other Madrones, the Pacific Madrone's bark peels in papery sheets, revealing new, orange or green bark. As the bark ages, it turns dark red. The Pacific Madrone tends to flower in clusters during the months March to May, producing pea-sized berries with many seeds that ripen in the fall. This Madrone is unique when compared to others because of its size and its elaborate, wide-spreading root system.
Since the genus Arbutus is entirely consisted of Angiosperms, all of the species have fruit to protect the seeds, namely berries. All of the species in the genus Arbutus reproduce sexually by seed. The Arizona Madrone is able to reproduce after being burnt down by growing from the root crown. The Texas Madrone uses the aid of 'nurse trees' to help the chances of success of the seedling. A nurse tree provides shade and water for the seedling, as well as marking the spot where there is fertile soil. The only species of Madrone to reproduce asexually is the Menziesii, or Pacific Madrone. While this Madrone does produce an average of 20 seeds per berry and 50,000 berries per tree, most of its reproduction is vegetative by sprouting. The Pacific Madrone's flowers are pollinated generally by bees, but a few hummingbirds have been spotted pollinating the trees. Its seeds are dispersed by birds, deer, rodents, and of course gravity. These seeds, however, have a very low success rate that is dependent on little disturbance to the forest floor. Even those that survive have a very low growth rate, two year old seedlings measure up to be only 4 inches tall.
The Arizona Madrone can be found in more places than only Arizona, such as New Mexico and Mexico. It tends to be found growing in canyons or on the sides of mountains around an elevation of 4,000 to 8,000 feet. The Arizona Madrone thrives in areas with nearly year-round sun and bimodal rainy seasons. The Pacific Madrone can be found further up north along the coast of the Pacific Ocean, its habitat extending from British Columbia to southern California. They tend to grow best on dry foothills where the soil moisture is low or on rocky bluffs with mild oceanic winters. Depending on where the Pacific Madrone is located, the rainfall varies greatly. Also, they cannot withstand very high levels of frost. The Texas Madrone's habitat range is located in New Mexico, Mexico, and Texas. Obviously, this Madrone is able to thrive while being exposed to a long duration of sun. This region only accumulates 16 to 30 inches of rain per year. The Texas Madrone is most commonly found in wooded canyons or on the slopes of desert mountains, around 4,000 to 7,500 feet elevation with well-drained soil.
The overall number of Madrones in the United States is rapidly decreasing, and the mortality rate of new trees has risen to 90%. The problem begins when the madrone is just a seedling, being killed by root rot, desiccation, predation by slugs, and frost. If the seedling survives to maturity, fungi and other types of disease-causing organisms can take a toll on the tree. Nattrassia magiferae, a fungus, causes cankers in the trunk of the tree, eventually leading to bark discoloration. The bark eventually peels off revealing the fungus spores inside cracks in the bark. Fusicoccum ausculi, also a fungus, attacks the branch tips, moving inwards until the branch turns completely black and dies. This fungus only attacks trees that are weakened by other diseases though. Phytophthora cactorum, a pathogen, causes root rot and is the most common disease observed in Madrones. The signs that the tree have this disease are its leaves turning brown, new leaves dying, and the bark turns dark brown or black.
- Arbutus menziesii Reeves, Sonja L. USDA Forest Service. 2007.
- Arbutus arizonica Pavek, Diane S. USDA Forest Service. 1993.
- Arbutus xalapensis Tirmenstein, D. A. USDA Forest Service. 1990.
- Arbutus menziesii soil environment Unknown. Sustainable Horticulture. 2008.