How to Grow the Melon Cactus

Melocactus

The Spruce / Kara Riley 

In This Article

The melon cactus (Melocactus) is a genus of cacti with more than 30 species. Growers enjoy these cacti for their aesthetically interesting cephalium, a bristly red or white structure that protrudes from the top of the plant from which pink to red flowers grow. Some say it looks like a Fez hat, which is why another common name for this plant is the Turk’s cap cactus. Fruits that are shaped like peppers follow the flowers and tend to attract birds and other wildlife. Young melon cacti do not have the cephalium; it only develops on mature plants. Prior to the appearance of the cephalium, melon cacti look like a basic cactus with a green round or cylindrical shape that has spines along it. It is best to plant the melon cactus in the spring. In general, these plants have a moderate growth rate, with some species growing faster than others.

Botanical Name Melocactus
Common Name Melon cactus, Turk's cap cactus
Plant Type Cactus
Mature Size Up to 3 ft. tall, 1 ft. wide
Sun Exposure Full sun
Soil Type Sandy, well-drained
Soil pH Acidic, neutral
Bloom Time Summer
Flower Color  Pink, red
Hardiness Zones 10–11 (USDA)
Native Area  Central America, South America
Toxicity Nontoxic
closeup of a melocactus
The Spruce / Kara Riley 

Melon Cactus Care

Melon cacti are somewhat finicky plants that must have their growing requirements met for them to flourish. They are best for growers who already know how to care for other more basic types of cacti. They need lots of light, warmth, and sharp soil drainage. 

Establishing the right watering routine is key for their care. They don’t like soggy soil, but they also shouldn't be left to dry out completely. Overwatering can damage or even kill the plant. But as long as you get the moisture level right, these cacti typically do not have any serious issues with pests or diseases. 

Light

These cacti need full sun to grow their best, meaning at least six hours of direct sunlight on most days. If you are growing them indoors, place the pot by your brightest window, and bring it outside in the warm weather if possible to get direct sun.

Soil

Melon cacti prefer a sandy or rocky soil with excellent drainage. Poor soil drainage can quickly cause root rot on a plant. For container plantings, a well-draining cactus potting mix should work. A slightly acidic to neutral soil pH is ideal.

Water

These cacti like a moderate amount of moisture. Give them some water whenever you stick your finger into the soil and it feels dry a few inches down. Don’t ever let the soil dry out completely, but be careful not to water so often that the soil is always wet.

Temperature and Humidity

Tropical temperatures are ideal for melon cacti. These plants aren’t cold hardy, and frost can kill them. A temperature above 70 degrees Fahrenheit is best. Protect your cactus from temperatures that drop below 60 degrees Fahrenheit, as well as from cold drafts such as those from an air conditioner. Humidity typically isn’t an issue for the plant as long as it’s in well-draining soil.

Fertilizer

Feed your melon cactus with a balanced cactus or succulent fertilizer during the spring and summer to boost growth. No fertilization is necessary during the fall and winter months.

Potting and Repotting the Melon Cactus

When grown in a container, the melon cactus likes to be a little cramped. Choose a pot that’s slightly larger than its root ball, and make sure the pot has ample drainage holes. An unglazed clay pot is beneficial because it also will allow excess moisture to escape through its walls. Plant the cactus with a quality cactus potting mix. You'll probably want to wear thick work gloves to do this to protect your hands from the cactus spines.

How often you have to repot your cactus will depend on the individual species’ growth rate and mature size. In general, repot when the roots have taken up all the container space and are starting to spill out. The best time to repot is in the spring at the start of the growing season. Select just one container size up for your plant. Gently ease the root ball out of the old container, and set it in the new one, filling around the roots with fresh potting mix. Be sure to replant the cactus at the same depth it was in the original container.

Melon Cactus Varieties

There are several species and varieties of melon cactus, including:

  • Melocactus azureus: This species is native to Brazil and sports a frosty blue body with white to brownish spines.
  • Melocactus broadwayi: This is a small species with a gray-green body and pink to purple flowers.
  • Melocactus concinnus: This is another small species that typically matures at only 6 inches high.
closeup of melocactus azureus
The Spruce / Kara Riley
melocactus with a red cap
Olga Korica / Getty Images