Plant Pollen and Pollination FAQs
Birds do it. Bees do it. And, nowadays we do it-- - pollinate our plants
that is. In case you did not know, the nation's Honey Bees have been devastated
by a major parasitic disease, along with overuse of pesticides. Farmers always
relied on Mother Nature and these little critters to do the pollination task.
Now, humans often need to play a supporting role. A number of companies are
thriving on the business of bringing bee hives into commercial farms and
orchards, to perform the task of pollinating crops.
While honey bees have been the major pollinators, there are also many insects
that act as pollinators. Some insects also perform the pollinating task in
search of nectar, while others actually eat the pollen.
One of the most frequently asked questions on the topic of gardens is around
pollination, in particular pollination problems.
Types of Pollinating Flowers:
Some fruits and vegetables are self pollinating. Self pollinators have both
male and female parts on the flower. Wind or insects spread the pollen easily,
from within the flower. This makes the pollination task easy, and good fruit
set is more often assured. An example of this is tomatoes.
Other plants produce both a male and a female flower. This requires bridging
a much larger distance to bring the male pollen to the stamen in the female
flower for pollination to occur. This is where the impact of a declining
bee population has been most seriously felt.
Identification of Male and Female Flowers:
Assuming all has gone well, your plant will begin to form flowers. In most
plants, the pollen laden male flowers will come out first. (Doesn't that
sound familiar?). They will often proliferate a few days, to as much as two
weeks, before the first female comes upon the scene. New growers worry that
perhaps there is something wrong with the plant, as no females have appeared.
This worry is heightened when talking with experienced growers, who invariably
will be a week or so ahead of the novice grower, and boasts of vegetables
and fruit already growing on their plants. Never fear, your plant will develop
female flowers, with tiny fruit attached behind them.
Male Flowers (below) are on a stem that is fairly thin, and usually
extends up above, or out from, the branch or vine. The center stamen contains
the pollen. Pollen is mature, if it readily comes off the stamen and onto
your finger.
Female flowers (below) are easily identified. A tiny baby fruit or
vegetable is located between the stem and the flower. The baby fruit is more
visible on larger fruits and vegetables, like cucumber or watermelon. The
female flower will be close to the vine, and the stem is noticeably shorter
than the male stem. In the center is a the "stigma", which must receive the
pollen in order for the fruit to develop. In the pictures below, the first
one is an immature female, and the second picture is a mature female with
an open flower ready to accept pollen.
Is Plant Pollination Occurring?
The affirmative answer is apparent several days later, when the female flower
has died and fallen off, and the tiny fruit beneath it begins to grow. The
presence or absence of Honey Bees and other insects is a clue to whether
pollination is occurring.
If pollination did not occur, the baby fruit or vegetable will shrivel and
die.
Poor pollination can also occur. Pollination needs to be made to all segments
of the female flower. If not, the fruit will not reach it's maximum potential,
and the number of seeds will be reduced.
There are other factors that affect good pollination, or "fruit set". Among
them are fertilizer imbalance, plant stress caused by too much or too little
water, and excessive heat or cold.
Also see: Poor Plant Pollination - causes and
cures
Nature's Way:
While the honey bee population is down, many other insects are pollinators.
Any insect that is attracted to the flowers on your plants are potential
pollinators. They only need to travel in the right sequence from male flower
to female flower.....the other way does not work.
Important: If pesticides are used, you are killing off the pollinators
in your area. If you use them, stop a week or two before the flowers emerge.
Do not resume spraying insecticides until the flowers are done blooming.
Remember, pesticides will kill off the pollinators, including the Honey Bee.
Hand Pollination:
Jokes about hand pollination abound, both in the internet, and in the field.
Does anyone object to helping their plant to have sex? Okay, with that said,
on to the learning....
By pollinating the flowers on your plants by hand, you assure a number of
things. First, you use pollen from a male plant you select (versus Mother
Nature- -random?). This eliminates cross and undesirable results in future
crops from the resulting seed. Second, it assures pollination of the female
flower, although nothing is nature is an ironclad guarantee. Third, it increases
the likelihood of pollinating all segments of the female flower. Multi-segmented
stigmas exists in the flowers of many plants. Proper pollination of all segments
makes for bigger and better fruit, and seed development in vegetable crops.
Step by step:
-
Time pollination for the first day that a female flower opens it's bud. You
can usually tell the night before when it is ready to open.
-
Pollinate the plants in the early morning. The flowers will close in the
afternoon, or towards evening.
-
Select a male flower. Pull off the petals to expose the Stamen, which contains
the pollen.
-
Make sure the pollen is mature. Touch the stamen with your finger, to see
if tiny specks of pollen come off on your hand.
-
Using the stamen itself (some growers opt to transfer it to a soft paint
brush), gently rub the pollen onto the inside stigma of the female flower.
Make sure to come in contact with all segments of the stigma.
-
Hand pollination is now complete! Was it good for you?(Ooops. Sorry, I could
not resist!).
Also see: Hand Pollination
Cross Pollination:
Cross Pollination from one plant of the same variety to another, is good
and healthy for a species. It is natures' way of ensuring the survival of
the species over time. Cross pollination of one variety to another variety
in the same family may be good, if you are experimenting with, or attempting
to create new varieties or disease resistant strains. But, it can be bad,
if you are trying to grow a pumpkin and a cross with a Zucchini accidentally
occurs.
In the first instance, cross pollination in nature exists to broaden the
gene pool of a particular species, be it animal (including humans) or plants.
The broader the gene pool, the more likely a subset of the population will
survive some future disease or bacteria. Botanists use cross-pollination
to seek and maximize a certain desired genes' occurrence in the population.
This includes disease resistance, size taste nutritional value, etc. The
resulting hybrids are made broadly available in agriculture. While enhancing
certain traits of the species, cross pollination in the latter case is narrowing
the gene pool, and thus increasing the risk to long term survival.
The popularity of "Heirloom" seeds draws upon a variety of almost forgotten
or lost strains of a species. They are very popular with avid gardeners who
seek to grow something different from the normal, something neighbors and
friends don't have.
Cross pollination across varieties of the same species is undesirable
in some cases. The cucurbita family ( squash, pumpkins and cucumbers) for
example, are notorious at cross pollinating. This is very common if you have
a variety of related plants species in your garden. It is also possible for
your neighbors' Zucchini pollen, to be carried by insects to your garden
and cross with a squash. The nearer the plants, the greater the likelihood
of cross pollination. The only way to avoid this problem, is to make sure
there are no cross-pollinators growing in the vicinity of your garden, a
difficult task for home gardeners who want variety. As a result, you will
likely live with an occasional half breed.
Saving and using seed from your garden is common among growers. If you suspect
cross pollination of your plants, buy fresh seed. The fruit of your current
crop will grow true. The cross is carried in the genes of the seed, and will
show up in plants of the next generation. If two or more of your fruit prove
to be a cross, pull up and discard the plant (unless by chance, you like
the result).
Also see: Cross Pollination
Fruit Set:
Fruit Set refers to the overall process of pollination and early growth of
a fruit or vegetable. Proper fruit set has occurred after pollination as
described above. But other factors affect the proper setting of fruit. The
emergence of male and female flowers is an important part of this process.
Your fertilization program can impact this. Early in your plants' life, an
emphasis on placed upon Nitrogen to promote leaf, vine and root growth. But,
too much nitrogen for too long a period may cause your plant to delay the
flowering process. If this seems to be the case, first check with other growers
in your area to see if their plants have begun to flower. Once you decide
your flowers are late, stop putting any fertilizer with nitrogen on your
plant for a week or two, and add more phosphorous.
A few other factors can affect fruit set. The most common is a mid summer
heat wave. High day and night time temperatures will cause plant stress.
The tiny pollinated fruit may abort as a result. A heat wave can also deter
bees from their job, making hand pollination more important. If your fruit
is shriveling and dying and you are in the middle of a heat wave, don't worry
or panic. As soon as the weather cools you will see new females appear and
successful pollination should occur.
While you can not completely cross out plant disease as a cause of poor fruit
set, it is far less likely. If your plant is visibly healthy, is growing
well, and you can find no evidence of disease, this is most likely not the
cause of poor fruit set. If you identify a disease problem, vigorously attack
the problem. Once conquered, you should find successful pollination and growth
even though it will be later in the season.
Related Topics:
Poor Pollination - causes and cures
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