The number of tomato plants in one pot, container, or planter box depends on the size of the box. The general recommendation is to plant one tomato plant per 5 gallons (about 0.5 cubic feet) of soil or potting mix.
Also consider the surface area and stability of your planter. Tomatoes can get big and bushy and need room for that growth, unless you prune them. As they get taller, they will need a stable planter to keep them from tipping over in the wind.
Self-watering planter boxes are especially useful for tomatoes, since they need a good supply of water to prevent tomato cracking (too much water) or plant stress (to little water).
The number of tomato plants recommended for specific planter boxes are:
- City Picker: 2 or 3 tomato plants in a self-watering planter box that is 24.5 x 20.5 x 9.5 inches. It uses 1.5 cubic feet of potting mix.
- EarthBox: 2 tomato plants in a self-watering planter box that is 29 x 11 x 13.5 inches. It uses between 1.5 and 2 cubic feet of potting mix.
- GrowBox: 2 tomato plants in a self-watering planter box that is 28 x 14 x 12 inches. It uses 32 quarts of potting mix, which is approximately 1.1 cubic feet.
- 5-Gallon Bucket: 1 tomato plant in a DIY (do-it-yourself) self-watering planter made from a 5-gallon bucket. It will hold about 0.6 cubic feet of potting mix. Here are some instructions on building your own from University of Illinois extension.
