T
here are several ways greenhouse plants get
pollinated — both by using natural and mechanical
methods. In some cases, of course, plants that don’t
require pollination are grown, or are propagated through
other means, but for those that rely on old-fashioned plant
reproduction, some very non-traditional methods have
been developed over the years.
Not all greenhouse crops need to be pollinated. Two
crops common to greenhouse production, however, rely on
it to be successful: cucumbers and tomatoes. Cucumbers
and their relatives (squashes, pumpkins, gourds, and
other cucurbits) produce male and female flowers.
Pollination of cucurbits can only occur when pollen
from the male flower makes contact with the female
flower. Plants such as tomatoes, have what’s known as a
“perfect” flower, meaning both male and female elements
are housed within the same structure, but even as such,
the pollen sometimes needs help hitting its target.
Insect Pollination
Just like in the great outdoors, some greenhouse plants are
pollinated by insects traveling from blossom to blossom.
Sometimes these beneficial insects find their way inside
through open ventilation, but many growers intentionally
release them to improve pollination in their greenhouse crops.
Bees are often the answer.
Honeybees are great pollinators, but few growers keep an
active hive inside their greenhouse. Many, however, do raise
them nearby and they will find their way inside during the
months they are active. Growers with no interest in taking care
of an active honeybee colony usually find eager, local beekeep-
ers in need of an additional location to place one of their hives.
The grower gets the benefit of pollination and the beekeeper
gets additional honey. Honeybees, though excellent outdoor
pollinators, are not always the best choice for greenhouse
pollination — this is where bumblebees come to the rescue.
Bumblebees are generally considered superior to honey-
bees in greenhouse environments for several
reasons. Both are relatively docile (if you have
ever been stung it was likely by a wasp or hornet,
not a bee), but bumblebees boast better vision
than honeybees which is useful in an artificial
environment where instinct alone may wholly
not serve them. They are also more adapt-
able to wider temperature ranges and envi-
ronments than honeybees tend to be. They are
more successful at pollination than honeybees
because they have a longer proboscis (insect
lingo for tongue) which collects pollen and nectar
from deeper-throated flowers. Their wing vibra-
tion, being a bigger insect than honeybees, also
fans and spreads pollen further than honeybees.
Honeybees and bumblebees are not the only
types of bees being pressed into the service
of greenhouse growers. Some are choos-
ing to use smaller bees like Mason bees or
Leafcutter bees. These two different species
will do the same thing but are active at
different times of the season. For early
pollination, Mason bees can be consid-
ered, and for mid-late season pollination, Leafcutter bees will
do the job. These smaller bees can crawl right inside of even
tiny flowers that some of the other types of bees cannot get
into. As the name implies, though, Leafcutter bees will “cut”
holes out of leaves to use in their nests. If leaf crops are raised
in conjunction with crops needing to be pollinated, Leafcutter
bees may not be the right choice in that instance.
Other beneficial insects released or nurtured in greenhouse
environments can help with pollination as well. Many predatory
and parasitic insects that growers may rely on for biological
pest control will often inadvertently aid in pollination.
Ladybugs, green lacewings, and a whole slew of other flying
and crawling “good guys” scour plant surfaces and undersides
for their next meal or haven for their next generation of progeny.
As they travel, they trample through pollen and nectar in
blossoms. Pollen sticks to their legs and wings, so they deposit
some elsewhere as they go about their business. Of course,
these insects should not be considered for their pollination
contribution alone, but they do provide a value-added service.
“ B e e s a r e o f t e n t h e a n s w e r. ”
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Maximum Yield