How Old or Large Does Golden Barrel Cactus Need to Be to Bloom?

Plant Appearance

• Although young golden barrels resemble mature ones, more of the green stem shows between the smaller spine clusters. As they grow, the spines become wider and more closely spaced. A golden barrel cactus grows slowly to a possible height of 4 feet and a width of 2 1/2 feet or more. Some plants form offsets around the base or sides, forming a multiple-headed clump. The plant's overall appearance is spherical, with old plants approaching broadly columnar. The wooly top of the plant is slightly concave in old plants. Mature golden barrels have as many as 35 ribs, each bearing a row of spine clusters, each containing three to five wide central spines surrounded by eight to 10 narrower radial spines.

Flowers

• The satiny, yellow flowers are cup-shaped, not opening widely. The petal tips are pointed. The flower is surrounded by dark brown, papery, sepal-like structures. Bees pollinate the flowers, with seeds forming in the base of the flower. The mature fruit, topped by the dark brown dried flower, can remain on the plant for a long time, so that the top of an old golden barrel can have multiple rings of old flowers. You can remove the fruits, take out the round, black seeds and germinate them to grow your own seedling golden barrels. According to D. G. Hessayon in his book, "The Greenhouse Expert," golden barrels are about 15 years old when they bloom for the first time.

Growth Rate

• A golden barrel cactus grown from seed usually takes three to five years to fill a 4- to 6-inch pot. Molly Thongthiraj, co-owner of California Cactus Center in Pasadena, California, was interviewed in a 2009 "Los Angeles Times" article and cited the growth rate for golden barrels as 1 inch per year, slowing as the plants near 36 inches in diameter. Plant nursery Advanced Arid Exotics finds that golden barrels reach about 10 inches wide after 10 to 15 years, 18 inches in 25 to 30 years and 24 inches in 40 to 50 years. They can live for 100 years or more.

Growing Conditions

• Grow golden barrels in full sun for best spine color and a compact shape. They are heat- and drought-tolerant, and accept most soil types but need a well-draining soil. Golden barrels grow in U.S. Department of Agriculture plant hardiness zones 9 through 11, but grow as houseplants anywhere. They are suited for container growing, but will eventually get so large they will be difficult to move. Allow the top 2 to 3 inches of the soil to dry out before watering the golden barrel, and be careful not to over-water it in winter when the plant isn't growing.