I want to grow capsicums upside down. Is this as effective as growing capsicums with the plant climbing up the supporting strings, as we do in greenhouses? How can I ensure a safe and efficient crop yield?

Given the current trend for growing upside-down plants, this is an interesting question with a few different factors that need to be taken into account. Generally, growing plants such as tomatoes and capsicums upside down may have a novelty value, but it does tend to reduce yields somewhat and leads to a few different problems.

First of all, while the plants are suspended upside down, they don’t really grow completely downwards and this is due to two plant mechanisms: gravitropism and phototropism. While gravity may be acting on the weight of the plant stems and pulling them downwards, inside the plant, the cells are also responding to gravity.

Stem tips respond to gravity by growing against it—upwards—while roots respond to gravity and grow downwards, even if the plants have been positioned upside down. After a few weeks, you’ll see the stem tips do a U-turn and start to grow upwards, away from the ground. Inside the planter pot, roots won’t grow upwards and completely fill the pot, they will concentrate at the base, which restricts water, oxygen and nutrient uptake.

Also, plants respond to light (phototropism), so the stems and leaves will orientate themselves upwards towards the natural light above, which results in a bent-looking plant with stems and leaves turning upwards as they grow.

For plants with flexible stems and a bushy growth habit, like tomatoes, this orientation still allows the plant to function and fruit. However, for plants with more brittle, woody stems and heavy fruit like bell peppers, this sort of unsupported, bendy growth often leads to stems snapping and fruit falling to the ground.

Plants with smaller, lighter fruits, and thin, flexible stems, like chilies, are better-suited to growing upside down. For larger fruits, growers can also use supports and strings to hold the stems as they develop large fruits on the upside-down plant.

Another issue with upside-down plant production is that pepper plants require high light levels, particularly in the winter. With the containers hanging above the plants, this shading effect lowers photosynthesis.

Also, the weight of the container, medium, plant and fruit would all need to be supported by the greenhouse structure. Finally, when watering the upside-down plant, the nutrient solution falls on the plant itself, which could cause problems down the road.

If you want to give upside-down bell pepper production a try, remember to support the developing fruits so they don’t snap off stems; avoid getting plants wet with drainage water; and space plants wider to account for the overhead shading effect. Even with these measures, yield reductions are likely using this method.