ASK THE EXPERTS
Q
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?
Thanks, Zubin
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 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
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 reduces 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 wide enough to account
for the overhead shading effect. Even
with these measures, yield reductions
are likely using this method.
Kind regards,
Lynette Morgan
Dr. Lynette Morgan holds a B. Hort. Tech. degree and a PhD in
hydroponic greenhouse production from Massey University, New
Zealand. Lynette is a partner with Suntec International Hydroponic
Consultants and has authored several hydroponic technical books.
Visit suntec.co.nz for more information.
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Maximum Yield USA | January 2016