Dracaena marginata prefers a soil that has a high nutrient content and is slightly acidic. Although the plant does best in humid conditions and likes moist soil, its soil must drain well. In poorly drained soil, the tree is at risk of root rot and other fungal diseases. The ideal soil for Dracaena marginata will contain loam to add nutrients, peat to lower the pH level and vermiculite or perlite to improve drainage.
Most garden supply centers have potting mixes for indoor plants. Although referred to as potting soil, most mixes do not contain soil because soil creates a heavy mix that doesn't drain well. Look for a potting medium that contains peat, vermiculite or perlite and some form of organic matter such as compost or bark. If you want to make your own mix for your dracaena, combine one-third compost or fine bark chips, one-third peat and one-third vermiculite or perlite. Because it may not drain well and can contain insects and disease, never use garden soil for your potted plants.
The container for your Dracaena marginata must have at least one drainage hole in the bottom. Without this hole, the soil at the bottom of the pot can become waterlogged, leading to root rot. To allow the roots room to expand, choose a container wide enough to allow 1 to 2 inches of space between the roots and the wall of the pot. Don't use a container that is too large since this can lead to over-watering. Because the tree has plenty of upper growth, it's best to choose a pot made of a heavy material such as terracotta or ceramic for stability. To make the tree easier to move, place the container on casters.
Dracaena marginata is native to the tropical island of Madagascar and thrives in humid conditions. To prevent mildew and mold, most homes are kept at low humidity. To boost the humidity around your dracaena and make it feel more at home, set the container onto a tray filled with pebbles. Fill the tray with enough water to keep the pebbles moist. The water level should only moisten the pebbles, not reach the base of your dracaena's pot.