On 8/24/2009 9:19 AM, Alistair Macdonald wrote:
Last year and the year before my mature (about 20 years old) Victoria plum
tree produced barely half-a-dozen fruits. This year I have harvested over
300 delicious plums. What, if anything have I done right, or do the
elements take the credit?



Some fruit trees develop alternating-year bearing. In a year of
abundant fruit, so much of the tree's nutrients are devoted to producing
fruit that little new fruitwood grows for next year's crop. In the
following year with scarce fruit, ample nutrients are available to
produce fruitwood for next year's crop.

Three things you can do to break this two-year cycle.

1. Prune the tree while it is dormant. Shorten new branches, and
remove some older branches. You don't have to cut as severely as if it
were a peach tree, but you want to cut enough to slightly reduce the
amount of fruitwood.

2. Feed the tree well just as the flower buds begin to swell. Don't
over-feed, but be generous. Feed again lightly after all fruit has been
picked.

3. When fruits begin to form after flowering, remove about half of the
immature fruit. Do this thinning when the fruit is about the size of
small cherries, uniformly throughout the tree. Thinning should increase
the size of the remaining fruit. However, the pits will not be any
larger; and it's the pits that require extra nutrients. The fruit flesh
is primarily carbohydrates, which are easy for a plant to produce. The
pits contain protein and oil, which are more difficult. With fewer
pits, more nutrients can be directed towards new fruitwood.

--
David E. Ross
Climate: California Mediterranean
Sunset Zone: 21 -- interior Santa Monica Mountains with some ocean
influence (USDA 10a, very close to Sunset Zone 19)
Gardening diary at http://www.rossde.com/garden/diary