Yolanda Vanveen of Kalama, Washington is a third generation flower gardener and sustainable gardener. Standing in her lovely kitchen surrounded by flowers from her garden, she tells in this brief video (2:15) how to grow tomato plants upside down in a container. What Yolanda doesn’t say is that this is a good way to make the most of a container, and also a way to obscure the bottom part of a hanging basket which is generally quite ugly when viewed from below.
It is important to choose a small tomato variety, such as Sweetie, as the large beefsteak varieties are simply too heavy. The fruit will fall off. A smaller variety makes more of a vine and an attractive plant.
Start your seeds in a seed tray indoors after the last freeze. Use a good, light seed starter mix with light soil and/or vermiculite. Keep the tray watered but not waterlogged.
When your little tomato plants are a few inches tall and has 3 or 4 leaves, transfer them to the container. Yolanda says it’s fine for tomato plants to share the container with other plants, such as hyacinth bulbs in the example she shows.
You can plant the plugs (nursery parlance for the seedling in its little plug of soil) in the top of the container as normal, or cut openings in the side of the container and plant them in there. You can do both, and then you will have vines growing out of the top as well as the sides. That will give you lots of tomato plants grown upside down.