Metal tubs can take on an attractive patina as they're exposed to the weather, adding an element of elegance to a potted vegetable garden. Metal is also nonporous, helping the potting soil retain moisture for more hydrated vegetables. Take advantage of these benefits when designing your next vegetable container for a lush and bountiful vegetable harvest.
Choose a metal tub. Containers come in various sizes. Small tubs with a depth of 10 inches are ideal for small plants like green onions or parsley, according to Texas A&M University. For most vegetable species, like lettuce and tomatoes, the university recommends a tub that can hold at least 5 gallons of growing medium.
Prepare the tub for planting. Drill drainage holes into the tub if it doesn't already have any. Place the holes along the tub's side, spacing them apart by 3 inches and approximately 1/2 inch from the tub's bottom. The University of Florida suggests painting the inside of the tub with asphalt paint. This is not critically necessary, but will help shield the tub's contents from heat as the metal warms up in the sun.
Pour 1 inch of gravel into the bottom of the tub for enhanced drainage, according to Texas A&M University.
Fill the tub with potting mix within 2 to 3 inches of the tub's brim. Ohio State University recommends using a commercially prepared potting soil mix. Alternatively, mix your own by combining equal parts of compost or peat moss, garden soil and sand or perlite.
Sow seeds in the potting mix. Bury the seeds 1/2 inch deep or as needed according to the requirements listed on the seed packet.
Water the tub twice daily or as necessary to keep the surface dirt moist. Most seeds will germinate within a couple weeks. Once the seedlings are established, reduce watering to once a day or whenever the top inch of soil becomes dry.
Fertilize the tub. Pour an ounce of 20-20-20 granular fertilizer into 5 gallons of water. Stir it thoroughly and use the fertilizer solution to water the tub's plants once every couple of days.
Mulch the vegetable plants once they're 4-inches tall or higher. Ohio State University recommends using an inch of mulch. Mulching materials include shredded leaves, grass clippings and compost.