It's called a barrel cactus because, as the name implies, they are almost perfectly round when juvenile, with evenly spaced rows of spines on their deeply ribbed lobes. As they grow, they may stretch out, becoming more oval than circular. This cactus can grow up to 6 feet tall when fully mature. They grow slowly, so small 3-inch indoor specimens will remain manageable for many years before getting large.
Barrel cactus can be grown indoors. They aren't difficult to grow as long as these plants have the brightest, sunniest location. Usually, southern-facing windows offer the strongest sun. These are true, extreme desert plants that cannot handle standing water. Plant them in very well-draining soil or potting mix.
They can produce flowers but usually won't start doing that until they are at least 6 inches wide, which can take about 15 years. Blooms get to about two to three inches wide and grow near the top of the barrel for about two to six weeks in the spring or summer. They usually do not bloom indoors since they require intense sunlight for flowering.
The trick for growing a barrel cactus is to ensure it has full sun exposure during its growing season. It also needs a phosphorus-rich fertilizer given at least once monthly.
Withhold water for a few months before the growing season. A simulated drought mimics its natural growth cycle in the wild. To encourage blooms in the growing season, give it water once a week when grown inside. This plant needs well-draining soil since soggy soil leads to root rot, potentially killing the plant. It thrives in a pH range of 6.1 to 7.5. Use a cacti/succulent potting mix for best results.
Barrel cactus are prone to root rot. From fall to spring, water infrequently (every month or two) and ensure that the soil drains completely. Do not leave any water in the tray or allow it to sit in water.
In winter, simulate drought conditions, giving no water. In early spring, gradually provide some water, increasing water to once per week in spring and summer, ensuring the water drains completely. Barrel cactus require air flow around the plant and low to no humidity. Ensure the plant is not in an airless zone. Air flow prevents golden barrel cactus from accumulating moisture.
Feed these plants every four weeks with a phosphorus-rich or low-nitrogen fertilizer. For the amount to use, follow product label instructions.
