On 4/30/2008 3:50 PM, bluesardine wrote:
We have a lemon tree in a pot on our terrace in Spain.
The leaves are turning yellow, it gets enough water, has stones in
bottom so not water logged, situated in bright sun all day.

Any ideas, Pete


Citrus requires excellent drainage. In a container, citrus should have
soil that is always moist but never wet. Stones in the bottom of the
pot are not sufficient. You really need drain holes.

Citrus also needs a slightly acidic soil with nitrogen, iron, and zinc.
Blotchy yellow leaves may indeed indicate a lack of zinc. Commercial
citrus fertilizers are acidic and contain nitrogen and iron, but many
fail to include zinc. You may have to special-order zinc sulfate; a 1kg
or 2kg bag should last for years. A pinch of Epsom salts (magnesium
sulfate) now and then may also be beneficial; it should promote the
branching of new shoots.

Feed lightly and frequently. Always make sure the soil is moist before
feeding and then water lightly right after feeding.

Once the plant seems to be recovering, it should have some phosphorus to
promote fruiting. Phosphorus does not readily dissolve and travel
through the soil; instead, it must be placed where the roots can find
it. Take a length of steel rebar or a thin stick and poke 3 or 4 holes
at least 25 cm into the soil about halfway between the trunk and the
edge of the pot. Fill the holes halfway with bone meal.
(Superphosphate might be too strong for the confined roots.)

See my http://www.rossde.com/garden/dwarf_citrus.html.

--
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 pages at http://www.rossde.com/garden/