Dragon tree (Dracaena marginata) is a low-maintenance houseplant that has few problems. The "Tricolor" cultivar, commonly called rainbow plant or rainbow tree, has cream and yellow stripes on narrow green leaves. With good light, dragon trees can grow up to 18 inches per year for the first few years, and may reach a height of 10 to 15 feet. Dragon tree is toxic to dogs and cats.
Dragon trees need moderate to bright indirect sunlight. Brown spots on the leaves usually indicate the plant is getting too much light. If the plant doesn't get enough light the leaves turn pale. Dragon trees like comfortable room temperatures of between 65 and 75 degrees Fahrenheit. Keep the thermostat set so the plant isn't chilled if you leave home for several days in winter. A sudden drop in temperature can cause the lower leaves to drop off.
Water and Fertilizer
A sure way to kill a dragon tree is to over-water it. Water the plant only when the top 1 inch of soil is dry and then water it thoroughly with room-temperature water. Never allow the base of the pot to sit in a saucer of water. Feed the plant with a liquid houseplant fertilizer every two weeks in spring and summer and monthly in fall and winter.
Repot rainbow plants every two years into a pot one size larger until they reach the desired height. After that, repot every three years into the same pot or a pot of the same size to refresh the soil. Use a general-purpose houseplant potting mix and remove as much of the old soil as possible without injuring the roots.