The soil in the container looks muddy and heavy like garden soil. Or, at least it appears so in the picture. If so, I'd say that the tree is having an extremely difficult time accessing air at the root system. Do you think that this is a possibility?

Was this tree moved from its normal location?
Has the soil been changed from what was used for a long time?
Has the amount of light this tree been getting changed?

Thanks to both rhizo and kimmrs.

The plant spent 6 weeks in my sister's home- I don't know in what position, whilst we were in the States (would you believe!). The soil is the same as all summer, but it is very damp, so yesterday I stood the plant on the floor of the conservatory which has gentle under-floor heating, to dry out as I did notice the trunk was wet 1" above the soil level. Should I feed it by spraying what leaves remain? Should I try repotting it- if so what should I use? Thanks

It may be that the tree dropped the leaves because the soil was simply too wet. Until you see new growth do not feed that plant anything because that will simply add to the stress the plant is already under.

Could be a number of things. What temps was it subjected to during it's move back and forth? That, combined with a change of light, change of watering regimen all could shock it into leaf drop. And I agree with rhizo, that looks like very heavy soil. How long have you had this plant?

tj

I planted a lemon tree in early 2008. The leaves are light yellow on ends and curled up. I feed it and I think it getting plenty of water. It gets plenty of sunshine. Please help

Evidently the friend looked at it differently. Was the tree removed to his residence. If so, the loss of leaves is a common result of a changing environment.
I suggest you not change its soil until the plant is ready to add new growth. Then, changing its soil and possibly going up one size of pot, will add to the encouragement the plant will use for spring growth.

AT this time, follow what fertilizer regimen you have done in the past. Citrus are heavy feeders and, much like the African Violet, can be fed with every watering. A fish emulsion or high potassium fertilizer can be given.

Sunlight at this time is very low and your citrus will benefit from being given as much, and as equally, as possible. Place it where it can receive the best light...a southern or western exposure and turn it 1/4 turn every day or so so that the crown receives all the sun it can use.