Shallow boxes and planters are ideal for gardeners who are working within the limited space of a windowsill or terrace garden. And certain species, like cacti, succulents and certain shallow-rooted plants, actually grow best in shallow soil. But plants in shallow containers have different requirements than plants grown in the ground. Shallow boxes contain a limited amount of soil, nutrients and water. Therefore, container-grown plants should be checked frequently to make sure their needs are being met.
Drill (with a 1/4- to 1/2-inch bit), hammer or poke several drainage holes into the bottom of your shallow box if holes are not already present. If the water in planting containers cannot drain readily, the plants are likely to develop root rot.
Cut a mesh screen with a pair of wire cutters so the screen fits in the bottom of your shallow box. This will keep your planter's soil from escaping through the drainage hole.
Fill the shallow box within 1/2 inch of its rim with a potting mix prescribed for use in planting containers.
Plant your plants.
Water the box with a gentle stream of water. Stop watering when water drips out of the box's drainage holes. The soil in a shallow box can dry out quickly. Check the soil's moisture level frequently (during the hottest months, a shallow planter may need to be watered as often as two times a day). The easiest way to do this is to stick your finger into the top few inches of soil.