Agriculture Reference
In-Depth Information
Other plants are
dioecious
. These species
produce male f flowers on one plant and
female f flowers on another. Therefore, it is
necessary to have as least one female plant
and one male in order to achieve fruit
production. Carobs, hollies and pistachios
are all dioecious. Only one male plant is
required to pollinate about five female
plants but this can depend on species and
climate. Suffice it to say, if you are after fruit
production, plant more females than males,
or if you wish to avoid fruit/seed production,
plant only males. This is often the case with
Ginkgo biloba
, the maidenhair tree whose
fruit smells disgusting - not a desirable
attribute in an ornamental tree, so male
plants are preferred. Unless the plants are
produced asexually, we are not
technologically advanced enough to tell
male from female at seedling stage.
Adherents of geomancy and dowsing have
their theories that may or may not be useful.
been selected and interbred resulting in very
different-looking plants (see Figure 2.13).
The cauliflower and the cabbage in Figure
2.13 can be grown from seed and 'come true
from seed' as the saying goes. This is only
because of millennia of seedling selection
and how the seed was produced; for example,
red cabbages were only allowed to be
Seedlings that 'come true' from seed
Some plants, many of them vegetables, are
open-pollinated such as tomatoes, lettuce and
beans. They have closed flowers and therefore
pollinate themselves. No other pollen apart
from their own can enter the flower and
cross-pollinate with it. These are our
inheritance of millennia of selective breeding
by farmers and gardeners.
Some seed-grown plants have been cultivated
for so long that even though they are the same
species, variations of the species have been
selected for different purposes. The species
Brassica oleracea
is a prime example. Cabbages,
cauliflowers, broccoli and Brussels sprouts are
all the same species. These variations have
Figure 2.13
Cauliflower (bottom) and red cabbage (top)
are the same species,
Brassicaoleracea.
Through selective
breeding, they have evolved into very different-looking
plants.
