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 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.
Types of Melon Cactus
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.
Pruning
You will very rarely need to prune this cactus. Only consider pruning if the plant has a diseased or dying section that needs to be removed before the rest of the plant succumbs to the same fate. Very carefully snip the section away with sharp pruning shears. Take care to protect your hands with heavy-duty gloves.
Propagating Melon Cactus
Though it is possible to plant a piece of melon cactus in a new pot and hope for the best, this propagation method doesn’t work well for this particular species. The best way to propagate melon cactus is through seeds.
How to Grow Melon Cactus From Seed
Growing melon cactus from seed can take a long time, but the results can be beautiful. Germination can take three to six months, or potentially longer, depending upon the temperature and soil conditions in your pot. When starting seeds indoors, do it in the late winter or early spring, so you have the advantage of natural warmth to help them along. Use sterilized soil that is designed for succulents. Fill the pots with soil, drop in the seeds, and then lightly cover those seeds with a thin layer of soil. Moisten the soil, cover them with plastic wrap, and place them on a sunny windowsill. Seedlings will need to grow for at least a year in their original pot before transplanting.
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.
Overwintering
These plants need protection from the cold, as a frost will readily kill them. Even a cold draft can be enough to damage the plants and stunt their growth. Keep them indoors in a very warm area during the winter.
Common Pests and Plant Diseases
Fungal diseases can strike this plant, even with good air circulation. Be prepared with a mild fungicide and apply it at the first sign of a problem. Insects that might affect your melon cactus include aphids, mealybugs, spider mites, or scale. These common plant pests can be treated with horticultural oil.
How to Get Melon Cactus to Bloom
Keep in mind that many varieties of melon cactus won’t bloom until they reach maturity, and that could take several years. With proper care, melon cactus will surprise you with blooms when the time is right.
