In article ,
D Z wrote:
Hi,
but what about in an environment with seasonal cycles, such as warm summers
and harsh winters? Would it be possible, as a quirk of nature, for a tree to
flower early in the year (spring), and then again in late summer?

Okay, here's the story. I may not have all the details right, so I
hope the more knowledgable will correct me.

Temperate climate plants that go dormant in the winter and bloom in the
spring have a chilling requirement, which varies not only by species,
but by individual. The plant has to be exposed to a certain number of
hours in a range of cool temperatures above freezing in order to break
dormancy, and in the cases of spring-flowering plants, bloom.
Normally, it takes until spring to accumulate these hours, and the tree
blooms then. Occasionally the weather in the fall may be unusual and
the tree blooms in the fall. The flowers are "wasted" in that there's
no time to develop fruit, and there will be none to bloom in the
spring. Fortunately, this seldom happens, but it's less unusual for a
few flowers to bloom in the fall. It's more common for Prunus spp than
for Malus, perhaps because Prunus spp normally bloom earlier.

An interesting aspect of this is that plants with a low chilling
requirement are not only those that originated in warmer temperate
climates, but some like apricots and walnuts that originate in extreme
continental climates like central Asia, where springs and falls are
short compared to summers and winters, so the numbers of hours in the
particular cool-but-not-freezing range are low. It can be hard to grow
these plants, and especially to get fruit from them in more moderate
but more variable climates because they may break dormancy too early or
even in winter, and have the flowers frozen or even the wood damaged
when the warm spell is followed by cold weather again.

"Charles" wrote in message
.. .

Mine has flowers and fruit most of the time. I'm in southern
California, the tree is a "Dorset Golden."

It's the nature of this type tree in this environment.

A lot of breeding work has been done, mainly in Israel, to develop
apple cultivars with a very low chilling requirement. Some years ago I
looked through a huge, heavy book that listed thousands of fruit and
nut cultivars and included among other data the chilling requirement.
Unfortunately, I can't remember the name or origin of this book. I
wonder if the data is now on the web somewhere.