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Saguaro in Lost Dutchman State Park, Arizona |
The saguaro
cactus Carnegiea gigantea grows into column that can be 20 metres high. It occurs naturally in the Sonoran Desert, in southern Arizona
in the USA and in Mexico. The
flowers are produced near the growing point at the top of the plant, or at the
end of an ‘arm’, from April to June.
They open at night, as bats pollinate them, so the best time to see the
flowers is in the early morning.
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Saguaro, Organ Pipe Cactus NM |
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Saguaro flower and buds |
Like trees, birds nest in saguaros. Gila woodpeckers and gilded flickers excavate holes high up in the column, and other birds will use one of their holes when it has been vacated. When a saguaro dies, the flesh rots away to leave a characteristic wooden skeleton with a lattice of holes. This wooden structure supports the plant in life.
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Saguaro, Organ Pipe Cactus NM |
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Cactus wood, Alamo Canyon, Organ Pipe Cactus |
Other cacti that
are tree-like include several in the Opuntia
group. Cylindropuntia bigelovii, teddy bear cholla, from the southwestern United States and Mexico,
grows as a branched shrub with a distinct trunk that darkens with age. The branches are covered with dense,
white spines, giving the plant a furry appearance, but it is anything but furry
to the touch. Pretty, greenish-yellow
flowers appear in early summer.
New plants are mostly produced from offshoots of mature plants: small
pieces easily become detached, blow around in the wind, and, when they lodge
somewhere, grow into a new plant.
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Teddy Bear Cholla, Lost Dutchman State Park |
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Teddy Bear Cholla flower, Joshua Tree National Park |
Opuntia chlorotica, the pancake
cactus, is also a tree-like plant, growing to more than 2 m high, with very
round pads and a thick trunk. It
also occurs in the southwestern United States and Mexico, growing in sand or
rock, usually on steep, rocky slopes, often in canyons. This example is from Mt Ryan, in Joshua
Tree National Park, CA. Like many
other prickly pears, it has yellow flowers.
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Pancake Prickly Pear, Joshua Tree National Park |
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