Old rusty tubs are an attractive option for container gardening because the tubs are deep and have a rustic, natural look. Growing strawberries in an old galvanized tub gives you lots of surface space for more plants, and most tubs are large enough that you can mulch spent plants for harvest the following season. The zinc and cadmium used in galvanization could pose some health risks, however, so you should prepare the tub and use the right kind of soil.
Make drainage holes in the bottom of the tub. Strawberries need very good drainage in order to avoid rot and other diseases. Use a drill or a hammer and nail to make holes all over the bottom.
Fill the container halfway with water to make sure it drains within a few minutes. If it drains very slowly, try setting the container on top of two pieces of 2-inch by 4-inch pieces of wood.
Line the container with durable plastic liner, such as the type used to line ponds. Make sure the sides and bottom of the tub are covered. The University of Washington Botanic Gardens warns that cadmium and zinc in the galvanization can break down into soil and be taken up by plants. While the iron and zinc in the metal are good for the plants, the zinc and cadmium are harmful to humans. The risk of poisoning from these elements in the plants is quite slim, however, even without the plastic liner, but the liner also protects the plants from the extreme hot and cold temperatures found in metal containers.
Use the nail to poke holes all over the bottom of the plastic liner. Set the tub in a place that gets at least six hours of full sun a day.
Fill the tub with potting soil. Strawberries prefer pH-neutral soil, so avoid potting mixes that contain a lot of peat or sphagnum moss. Additionally, acidic soil can cause the galvanized metal to break down more quickly, which will shorten the life of the tub and increase the risk of harmful elements leaching into the soil through the holes in the bottom of the liner.
Plant the strawberry seedlings 10 to 14 inches apart after the last chance of hard frost has passed. Since the plants' roots will be exposed while you're putting them in, the University of Illinois Extension Service recommends planting them in the late afternoon or on a cloudy day to prevent drying.
Make the planting holes deep enough that you won't have to smash the roots to get the seedlings in the ground. Cover the roots just to the top, but do not cover the crown between the roots and stems.
Water in the seedlings by gently pouring water around the bases of the plants. Make sure you don't expose the roots when you water.