Cacti don't save up for rainy days; it's the sunny days that need saving up for!
Cacti are truly amazing plants. They live in some of Earth's harshest conditions and can survive severe drought and unstable weather. The majority of earth's cacti are endemic to North and South America, species that have developed over the last 50 million years.
Through millions of years, cacti have developed several adaptations that allow them to flourish in deserts. Most cacti develop extensive root systems can seek groundwater and trace minerals from far beneath the surface. Surprisingly, even in the desert, water can often be found deep underground. The thick fleshy stems hold water for times of drought. In addition, many cacti have fluted stems with deep ribs. These allow them to soak up and release water with no damage to the stem. Most cacti don't produce leaves. Instead, they use the stems to photosynthesize and produce sugars. This also makes it more difficult for animals to eat the "leaves". The spines on cacti serve two purposes. First, they ward off predators that might consume the cacti's precious water. Second, they help keep the cacti cool, by creating a blanket over the stem. Old Man's cactus is a case in point. Cacti produce flowers after a rainfall, but most cacti only keep their petals for a couple days, because this prevents excess water from evaporating from the petals. In some extreme cases, cacti flowers only last one night.
OLD MAN CACTI
What makes the old man cactus unique is its unusual spines. Unlike the spiky spines of other cacti, it is more like wool that got caught on a cactus. The fur-like spines help shelter the cactus from the blazing sun and intense heat. At night, it helps retain the daytime heat.
ORGAN PIPE CACTUS
The organ pipe cactus is a rapid growing, tall cactus. At maturity it can reach 20 feet. It blooms with whitish pink flowers which produce edible fruits.
The saguaro is truly the desert giant of the United States. Full-grown saguaro cacti can tower 10 meters above the desert floor. The saguaro cactus forms "forests" of cacti that support unique ecosystems.(see image below.)The saguaro cactus provides shelter for animals such as the desert owl, fruits as food for local wildlife, and nectar for insects and bees. After the cactus dies, it provides a home for insects. Also, after the cactus flesh decomposes, long cactus sticks are produced. These can be used by the local people. Saguaro cacti can form "monstrose growth"; a natural mutation creating unusual shapes in select specimens.
FISHHOOKS and PINCUSHIONS
Fishhooks and pincushions, as depicted by their name, have raised nipples rather than ribs like most other cacti. They also have thorns that are shaped like pins and fishhooks.
The "living stones" succulent is native to South Africa. The stone-like plants need no water from fall to spring. Near the end of the growing season, white flowers appear, producing dust-like seeds.
Barrel cacti are distinguishable by their barrel-like stems. As you can imagine, barrel cacti have adapted to store as much water as possible, thus taking the shape of a rain barrel. After a rainfall, barrel cacti flowers appear, though only for a short time. Most are of beautiful, bright colors. Barrel cacti tend to have hook-like spines to deter desert animals from eating their water-rich flesh.
While not a cactus itself, the monkey-puzzle tree inhabits dry regions of the Western United States. The name says it all. The monkey-puzzle tree is so snake-like that it would make it difficult for even monkeys to climb. The monkey-puzzle tree is considered to be the most primitive conifer. Its unusual, bizarre shape is intriguing to collectors and spectators alike. Although endangered in the wild, it is cultivated in various regions. It has an irregular, slow growth pattern.
The prickly pear cactus extends over a very large portion of North America. There are over 100 species with overlapping ranges from zone 3 (Central Alberta, Canada), through temperate and tropical (Central America). The prickly pear cactus is also used agriculturally. The prickly pear cactus is farmed in Mexico for both it fruits and its stems which are edible when young. What a unique way to farm in the desert!