It's a complaint that's as old as the hills:
My avocado tree is tall and green and
healthy but it doesn't want to bear fruit.
The possible reasons for this are:
You planted a pip: Trees grown from seed
can take up to 15 years to start blooming
and bearing fruit (or can even not bear at
all), while grafted nursery trees will reward
you with fruit within 3-4 years.
You have the only tree in the
neighbourhood: Avocado trees produce
perfect flowers which at different times are
first female (therefore 'receiving' pollen)
and thereafter male (releasing pollen).
When flowering occurs it's important to
have both types of flowers in order to
improve pollination. Therefore, the more
trees in the area, the better.
Your tree is 'normal': Even avocado
farmers complain about erratic crop with
fewer and smaller fruit. Researchers are
currently investigating the effects of climate
change (also at micro level), as well as new
grafting and pruning methods.
Growing tips
Plant a grafted tree: The most popular
varieties, which are available from local
growers, are 'Fuerte', with it's thin, green
skin, the more nutty 'Hass', which turns
purple-black when ripe, and 'Ryan'.
Avocado trees have a relatively shallow
root system, and the soil should therefore
be loose, sandy and fertile, but above all
should drain well. The trees need a lot of
sunlight, particularly when the flowers start
forming, and don't do well in regions that
experience strong winds during flowering
or when the fruit are still small. Frost
should also be avoided.
Plant a pip: Wash the pip and insert three
toothpicks into the top third (the pointed
end facing up), so that you can suspend
it over a glass or vase of water, with the
broad base facing downwards. Keep the
vase on a windowsill where it will receive
a lot of light (but the minimum of direct
sunlight) and regularly top up the water so
that the bottom third of the pip is always
submerged. After 2-3 weeks the pip will
begin to crack and during the following
month will first produce a root and then a
stem. When the shoot is 10-15cm long and
the roots have become thicker, you can
pinch out the growth point and transplant
the pip into a pot containing one part
sand, two parts potting soil and one part
compost. Incidentally, avocado trees are
also attractive house plants.
Pests and plagues
If you detect any illness or insects,
discuss this with your nursery. If the
leaves turn yellow, it's likely that the tree
is receiving too much water (allow it to dry
out for a few days). If the leaves turn brown
and brittle at the tips, it's possible that the
soil is too salty.
Sources
www.avocado.org
www.thegardenhelper.com/avocado.html