On Mon, 31 Jan 2005 17:50:18 -0000, "andrewpreece"
wrote:

Last year, for the first time ever, I had a red berry on my Magnolia tree.
There are no other Magnolias in the immediate area, and I am wondering if
the berry appeared because some errant bee had visited a Magnolia some
distance away and then managed to pollinate a single flower on my tree?

I ask because I think that this year I would like to collect some pollen
from anothe Magnolia and see if I can get more berries on my tree ( I think
it would increase the attractiveness of the tree, which is actually rather
dull except in spring ). Of course, I'd only be able to pollinate a few
flowers but it would be an interesting experiment, if it works I might get a
second Magnolia for pollination.

Andy.

Treseder ('Magnolias', Faber&Faber 1978) says:

"When the flowers open, the reproductive organs become fully exposed
and the stamens split and shed their pollen, but by this time the
stigmas have withered and become dry for they are usually only
receptive while the flowers are closed....... It has been found that
they are largely pollinated by flower beetles (Nitidulidae species)
which crawl between the overlapping tepals into the warm sheltered
environment of the flower chamber, and it is probable that other
insects likewise seek food and shelter there. It seems likely that
they can only assist in pollination when they have previously visited
older flowers and become smeared with pollen."

and

"Fertilisation does not occur until the pollen grains have germinated
on the receptive surfaces of the stigmas and the male nucleus cells
have fused with the female egg cells in the ovaries within the
carpels. In magnolias there appears to be a critical temperature for
pollen germination and with some magnolias this could be as high as 70
to 80 deg.F, an air temperature seldom if ever attained in British
gardens in April and May. While lower temperatures are apparently
adequate for pollen germination on many of the Himalayan species, some
of which begin to bloom among deep snow drifts in their natural
environment, one rarely finds fertile fruit cones in British gardens
on such magnolias as M. stellata, M. denudate and M. liliflora, or on
any of the American species, some of which can produce quite
spectacular displays of fruit cones in the eastern states of America,
as do the Asian species just mentioned."

and

"Apparent self-incompatibility recorded.....for a wide range of
magnolia species, is more recently attributed to the absence of
pollinating beatles at the brief and critical period of pollen
shedding."

From the above, I conclude that the flowers are only receptive to
pollen while closed or possibly for a very short time after they open.
Pollination is by insects that enter the flower before it opens, and
the British climate is not conducive to successful pollination. The
flowers may or may not need pollen from other specimens.

How all this fits with your magnolia setting a seed pod last year I'm
not sure. Perhaps the spring was particularly warm. Whatever it was
that caused the pod to set, it doesn't seem as though you could count
on it being a regular occurrence, whether by self pollination or by
pollen from another specimen.


--
Chris

E-mail: christopher[dot]hogg[at]virgin[dot]net