Golden barrel cactus (Echinocactus grusonii) is a spiny, ribbed cactus that grows in an unbranched spherical or cylindrical form. It is hardy in U.S. Department of Agriculture plant hardiness zones 9 through 11 or only in zones 9 and 10, depending on the source. Golden barrel cactus makes an effective focal point in a desert garden, although its slow growth calls for patience on the part of the gardener.
A golden barrel cactus produces seeds in papery seedpods that develop from flowers at the plant's top. The seeds are sown in spring when the temperature is about 70 degrees Fahrenheit. Sow the seeds on the surface of loose, sandy soil in a sunny location. Because the seeds need light to germinate, they shouldn't be covered, and the soil needs to remain moist while the seedlings are small.
A golden barrel cactus seedling grows relatively quickly, within a few years, to about 4 inches in diameter. During this stage, the plant is a dense spiny ball. Its spines emerge from protruding tubercles so that the ribbed structure that will become apparent as the plant matures is mostly hidden. The young cactus needs careful watering to remain healthy. It needs plenty of water in summer and tolerates moisture better than most cacti, but excessive water in winter causes it to rot.
As the plant matures, its growth rate slows markedly. At maturity, the specimen may be about 3 feet in diameter, but it requires decades to get that big. On the mature plant, the 20 to 40 ribs running from its top to its base are apparent. Its spines grow along the ribs from yellow areoles, which are small bumps common to all cacti that produce spines, flowers or offset shoots. The golden barrel cactus' spines are also yellow. When they're back-lit in brilliant sunlight, they produce the golden glow that gives the plant its name.
A healthy golden barrel cactus begins producing flowers when it is about 15 inches in diameter. The flowers emerge from a wooly patch at the cactus' top in spring and bloom into summer. The flowers are bright yellow, but they're small and not terribly conspicuous. By the end of summer, the flowers have produced seeds, completing the plant's reproductive cycle. The cycle continues to the end of the cactus' natural lifespan, which is usually fewer than 100 years.