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Plant Highlight: Ferocactus pilosus
Most of the cacti commonly referred to as “barrel cacti” belong to the genus Ferocactus, and these are found in the southwestern United States and through much of Mexico. They may be single-headed or clumping, with the individual stems ranging from softball-sized to towering columns 13 feet tall (4 m). One of the large species is Ferocactus pilosus, found in north-central to northeastern Mexico.
Although Ferocactus pilosus can sometimes be solitary, it usually forms clumps of a few to many stems, with the tallest ones attaining heights of up to 10 feet (3 m). Each stem has 13 to 20 ribs (this is the term used for the vertical ridges running up the length of the stem), with the spine-bearing areoles closely spaced along the tops of the ribs. The areoles are oval in shape and felted. The plants are deep green in color, but the spines add red and a touch of white to the mix, since the stout and prominent central spines are red, while the wispy radial spines are white. The 6 to 12 flattened central spines vary considerably in size, but the longest are up to two inches long (5 cm). These spines are not smooth, but are incised with tiny horizontal grooves, like miniature wash-boards. They are straight or slightly curved, and radiate in all directions. Around the outside of the areole are the white, hair-like radial spines, curling and twisting this way and that. They range from numerous to few, and occasionally they are lacking altogether.
The main flowering time for F. pilosus is spring, mostly in April and May, but sometimes starting in late March or continuing into early June. Occasionally, plants will put out a few flowers later in the year, but this is not typical. The flowers emerge from the tops of the areoles, just above the spines, and they are like vivid orange cups with pools of yellow pollen filling their centers. The petals are short and held upright, not spreading like those of other Ferocactus species. The flower diameter is up to an inch (2.5 cm).
The fruits of Ferocactus pilosus are oval and about 1.2 to 1.6 inches long (3 to 4 cm), with small rounded scales on the outside and the withered remains of the flowers persisting on their tops. The pulp within contains glossy black seeds which are .07 inch in diameter (1.75 mm).