University of Vermont Extension
Department of Plant and Soil Science
Summer News
Article
PLANT
BREEDING
FOR GARDENERS
Dr. Leonard Perry, Extension Professor
University of Vermont
Many new flowers have been created
by home gardeners including those in such large groups as iris, roses,
daylilies, and gladiolus. Creating new
selections at home through plant breeding is simple for many flowers if
you
know a few basic principles.
New flowers in home gardens can be
selected from sports or mutations of existing plants, selecting new
varieties
that arise naturally through crossing by wind and bees, or by
controlled
“crosses”. The latter is what “plant
breeding”
means. The crosses refer to the
controlled placement of pollen from one flower onto the receptive part
of
another, called the “stigma”. The stigma
is generally the thicker central structure in the center of flowers,
often
shaped like a tube or narrow vase.
To be successful, a cross must be
made when the pollen and stigma are at the right stages.
Generally when the pollen is ready, so is the
stigma. The main indicator of this is when
the flower is ready to open, or just opens.
The stigma often may be moist or sticky at this time in order to hold
the pollen once transferred by bees, or by you.
The easiest way to transfer pollen
is by a toothpick. You’ll find the
pollen on the “anthers”—the flower parts on very
slender stalks called
“filaments” that surround the central stigma.
Sometimes these may be on the sides of flowers as in roses or
lilacs. Just rub some pollen on the
toothpick from one flower (the male parent) and transfer it to the
stigma of
another (the
female parent). Or you can pick the male
flower and then rub its anthers onto the stigma of your female parent.
Timing is crucial, as once a flower
opens, if both pollen and stigma are present it may go on and cross
before your
controlled cross. To avoid this, just as
the flower is opening or even before it opens on the female parent
you’ve
chosen, slit the petals and remove the anthers.
This process is called “emasculation”.
Then, to further avoid pollen coming from another flower not of your
choosing onto this one, cover the flower with a small paper bag held
with paper
clip. Remove the bag to make your own
pollination, and then recover to avoid any further contamination by
foreign
pollen.
If your cross is successful, a seed
will soon begin to from. Harvest seeds when
ripe, which usually is when the seed covering or pod begins to change
color or
turn brown. Then sow as you would any
other flower seed. Sowing fresh seed
often is best, and avoids many germination and dormancy problems.
Keep in mind it may take a year to several
from sowing to bloom.
Be aware that flowers vary, with
some only having a male or female part.
Many of our newer hybrids, especially of annuals, may be sterile or
unable to be crossed if they don’t have the needed flower
parts. Petunias are often “male sterile”, having no
viable pollen. Others such as marigolds
or chrysanthemums may be difficult to work with. You may need a
hand lens for some such as
sweet peas, or tweezers to hold the filaments such as with
gladiolus. Daylilies and lilies are generally large and
easy to work with, good plants to start your plant breeding.
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Perry's Perennial
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