Watermelon peperomia (Peperomia argyreia) is appreciated for its rounded, fleshy leaves marked with silver and dark green stripes that resemble the markings of a watermelon. Watermelon peperomia is a low-growing plant that reaches only 6 to 8 inches tall at maturity. Although the plant is usually grown as a houseplant, it grows outdoors in the warm climates of U.S. Department of Agriculture plant hardiness zones 10 through 12. Usually, watermelon peperomia is grown in a container so it is easy to move indoors when temperatures drop below 60 degrees Fahrenheit.
Growing Conditions
Watermelon peperomia is well suited for planting in containers or hanging baskets. Drainage is critical, so make sure the container has a drainage hole in the bottom. Peperomia grows in any good-quality, regular commercial potting soil or a homemade mixture containing ingredients such as compost, loam or peat moss. A handful of sand or vermiculite promotes drainage.
Sun
Watermelon peperomia thrives in bright, indirect sunlight. Although most types of peperomia thrive in bright light, too much light fades the bright colors of the variegated foliage. Indoors, a window with an eastern exposure provides excellent light. Outdoors, grow the plant in light shade or filtered light.
Water
Watermelon peperomia is a tropical plant that prefers humid conditions but is prone to stem rot in soggy soil. Water the plant deeply when the top of the soil feels slightly dry. Let the pot drain completely and never allow the plant to stand in water. Check outdoor plants daily during warm weather. In fall and winter, water sparingly and allow more time between each watering so the soil has time to dry a bit more than usual. If the air is dry in summer, increase humidity by setting the container on a humidity tray -- a tray with a layer of wet pebbles.
Temperature
Watermelon peperomia does not tolerate freezing temperatures. If you take your plant outdoors during warm weather, bring it in as soon as nighttime temperatures drop to 60 to 65 F. Ideal temperatures for the plant are 85 F during the day and the low 60s F at night. Although the plant tolerates cooler weather, it will drop its leaves when temperatures drop below 50 F.
Fertilizer
Watermelon peperomia is a light feeder and too many nutrients may cause excessive growth and a leggy, spindly plant instead of a compact, bushy plant. Fertilize the plant once a month during spring and summer, using a balanced, water-soluble fertilizer. Avoid granular fertilizers, which are too strong and may scorch the plant.