Mature Bulletin No. 677-A April 28, 1962
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation
In the deserts of our southwestern states and Mexico the blazing sun,
scorching winds and scarcity of water make survival of any living thing
a serious problem. The unique native plants, dependent upon what
moisture they can absorb during the few rainy days each year, appear
outlandish because they are peculiarly adapted for existence there. It is
a land of thorns. Spiniest of all, most bizarre, and typical of the desert,
are the Cactuses.
Nearly all cacti, instead of leaves that would lose precious moisture by
evaporation from their pores, have thick succulent stems which
manufacture the plant food by photosynthesis. Most of them are
cylindrical or hemispherical plants and therefore have a minimum of
exposed surface. Any wound on the leathery skin is sealed by the sticky
juice inside. About 98 percent of their weight is water and some also
have enlarged tuberous roots for storing it.
The needle-sharp spines are another protective feature. Presumable, at
some stage in the evolution of cactuses, spines appeared on certain
kinds which, avoided by prehistoric grazing animals, increased until
now almost all species are armed with them. The location, numbers,
size, shape and color of the spines vary considerably, according to the
species. Some are beautifully decorated.
Another remarkable characteristic is that cacti produce flowers as
beautiful as those of any other group of plants in the world and, in
springtime, many desert regions become gay with their colorful blooms.
In size they vary from the little white blossom on a mushroom-like
Mescal Button to those on one of the Night Blooming Cereus cacti: a
foot in length, 15 inches in diameter, and as fragrant as a giant water
Many cactus flowers are cup-shaped, others are funnel-shaped, and
most of them have numerous sepals with colors shading into the
brilliant scarlet, purple, yellow or snowy-white petals. They are very
sensitive to light, so that on some kinds each flower blooms for only a
few hours or a single day, and those of the hedge cactus and the cereus
cacti only at night. On many species the fruit, eaten by birds and
mammals, is also colorful and some, such as the "tunas" of several
Prickly Pears, are delicious.
The Cactus Family includes over 1000 species and they are native only
in the Americas. The wide variety of types and shapes is indicated by
the common names for some of them: barrel, organ-pipe, old man,
hedgehog, snake, mule, beavertail, rat-tail, lemon vine and pincushion.
Most kinds, of course, occur on hot deserts, rocky mesas and nearby
mountain slopes. However, some grow at high altitudes in the Rockies
and the Andes; about 40 species are found in the swamps and keys of
Florida -- including the spineless Mistletoe Cactus with aerial roots and
branching stems dangling from trees on which it grows; others occur in
the West Indies, Brazil, and as far south as the Straits of Magellan.
Various kinds of prickly pear cacti (Bulletin No. 649-A), with jointed
stems of flat oval pads, are native in Massachusetts, Alberta and British
Columbia as well as Illinois and other grassland states.
East of Tucson, Arizona, the Saguaro national monument protects a
great number of our largest and most spectacular cactus. The Saguaro
becomes 40 or 50 feet tall and probably 200 years old. The cylindrical
trunk, fluted with from 20 to 25 spiny ridges, may be two feet or more
in diameter and have from one to a dozen upright branches. Tiny elf
owls nest in holes originally excavated in them by Gila woodpeckers.
The crimson fruits are edible and Indians grind the seeds into meal. The
white blossom is the state flower of Arizona.
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Update: June 2012