Calathea plants are houseplants commonly called zebra plants. They are so named for their bright white veins that look like zebra stripes on shiny dark green leaves whose undersides are purple-tinged. Varieties of calathea come with leaves that are white, yellow, rose or olive green. Calathea plants will not survive at temperatures below 55 degrees F.
Grow zebra plants in low light. Do not expose them to direct sunlight because it can burn their leaves. Situate them well away from windows, especially south-facing windows.
Grow your calathea plants indoors at temperatures between 60 and 70 degrees F. If your indoor temperatures are warmer than this, provide them with extra humidity. Keep calathea plants away from drafts.
Increase the humidity in the room where you are growing calathea plants. Situate them on pebble-filled saucers. Fill the saucers up with water to just below the level of the top of the rocks. The evaporating water will increase humidity in the area around the plant. Another way to increase humidity is to run a humidifier in the room.
Water with room-temperature water when the soil is dry one to two inches below the surface. Don't allow the soil to dry out completely. It should still be moist in the center of the root ball when you water it. Zebra plants hate wet feet--don't let them sit in standing water. Water less in winter; the soil will dry out more slowly and won't need as frequent watering as during active growth in summer.
Repot calathea yearly into a pot only slightly larger than the one in which they are currently growing. Use one part regular potting soil and one part perlite to retain moisture and promote good drainage.
Fertilize with regular indoor houseplant food every week during the period when they are in active growth. Apply weekly, mixing the fertilizer as recommended by the manufacturer.
Move calathea plants outdoors during frost-free weather, as soon as temperatures stay warmer than 60 degrees F. Place them in deep shade.