Growing in planters, whether vegetables or ornamental flowers, allows you to garden even if you have very little suitable space. Buying enough containers for all your plants can get expensive, especially if you need larger sized ones. Milk crates are inexpensive if purchased and free if you have access to the stock from a closed dairy. You can use the actual heavy duty milk crates or the ones sold as storage cubes at home and department stores.
Wash used milk crates in soapy dish washer then rinse of the soap residue. Mix one part bleach to nine parts water and rinse the crates in this solution to sterilize them after washing.
Cut a piece of black plastic mulch long enough to line the crate with 3 to 4 inches of overhang. Push it into the crate and fold the overhang over the rim. Secure the plastic in place by wrapping a bungee cord around the rim or by clipping it to the rim with binder clips from an office supply store.
Poke six holes in the bottom of the plastic, spacing them equally apart. This supplies drainage for the planter.
Fill the lined milk crate with soil-less potting mixture to within 2 inches of the rim. Make your own by mixing one part peat moss, one part sterilized compost and one part vermiculite. Add any slow-release fertilizers to the potting mix that are recommended for the type of plants you are growing---generally ½ cup of a balanced granular fertilizer.
Water the potting mix until the water drips from the bottom drainage holes to ensure it is evenly moist throughout. Plant into the milk crate your transplants, planting them at the same depth they are at in their nursery pots.