Fruit Growing
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The following is an excerpt from
Agriculture Canada Publication 1899/E, Producing apples in Eastern and Central
Canada. For a full copy of this report, check the Atlantic Food &
Horticulture Research Center web site.
Pollination is the transfer of
pollen from stamens of one flower to the pistil of another compatible flower,
which initiates seed formation. There is a positive relation between seed number
and successful competition for available nutrients, resulting in larger fruit
size and an increased probability that the fruit will remain on the tree until
harvest. Seeds are also associated with increased calcium transport into the
fruit, which is in turn associated with greater firmness, delayed senescence and
a reduced incidence of storage disorders.
Apple trees are essentially
self-infertile, so it is necessary to provide pollinizers. For a cultivar to be
considered a good pollinizer, it must produce compatible pollen of high
germinability in sufficient quantities and at the appropriate time.
The pollinizer must bloom at the
same time as the main crop cultivar. It is common practice to plant early
blooming cultivars with others that bloom in early or mid-season, and to plant
late blooming cultivars with those that bloom in mid- or late-season. The date
of full flower, when the greatest proportion of flowers are ready for crossing,
is more important than the date of first flower in determining overlap.
Wind is not an effective
pollination agent. The presence of bees is needed to disseminate compatible
pollen for satisfactory fruit set. Wild bee species are seldom present in stable
or high enough numbers to be reliable. This unreliability is unfortunate because
some species, such as bumble bees, are very efficient pollinators, as they are
active under windy or cloudy conditions and forage indiscriminately over the
orchard. In contrast, honey bees require slightly warmer and calmer conditions.
They also prefer to work flowers of the same species at one time. Honey bees
also generally move to the closest suitable flowers and will therefore remain
within rows rather than moving from row to row. The use of honey bees is
presently the most practical method of increasing the pollination force when it
is needed.
The following steps can be taken to
improve activity:
• Shelter orchards from wind
• Plant pollinizers at
sufficiently close intervals within crop rows or grafted into crop trees
•
Control weeds before introducing bees, as some weeds, such as dandelions, are
more attractive to them than are apple blossoms
• To ensure pollination of
the king blossom, the earliest in a cluster, bring bees into the orchard when
the first blooms are open and leave them until petal fall
• Put in place a
sufficiently high population of bees, as a higher concentration of bees
encourages each bee to travel farther between forages
• Use at least two to
three colonies per hectare in standard orchards, and five colonies per hectare
in high density plantings or in orchards where fruit set has been inadequate
• Place colonies in groups of five to fifteen at about 120m intervals in
areas sheltered from the wind, but if the bloom is light, distribute them
throughout the orchard
• So the hives catch the morning sun, place them with
their entrances facing east or south
• Avoid using any pesticide sprays
during the bloom period because these can adversely affect bee and pollen
viability
• Provide a source of clean water, as casual water sources within
the orchard may be contaminated