[Little Miss Muffet]

in my parents house we have a apple tree for the last 10 years it has only produced fruit on one side then the next year it will produce fruit the other side.
its a very old apple tree and you can not eat the fruit.but i have never come across this before and just wondered if this is comman or can any one tell me why this occurs.

[Aunt Sally]

Biannual bearing on an apple tree is very common.  Growers thin out the fruit in a good year to improve the crop in the bad year.  

Your old tree is probably quite large and a tree is not like and animal (yes really). The right limb does not necessarily know what the left bough is doing  

[Annie]

Wly cann`t you eat the fruits?I agree about the biennial growth but not about the fruit.Do you have any idea about what variety it is and what time of year are the fruit ripe?

[Little Miss Muffet]

the tree is large its also very old i can remember it being there when i was a child so its older than 30 years.
the fruit on it is smallthe apples are about the size of a golf ball and they stay hard and are sour i will get a photo of it in a couple of day and post on here it just looks odd as its like someone has taken all the fruit off one side yet the other side is blooming

[paintedlady]

sounds like a crab apple - they make great wine!

[Aunt Sally]

or possibly quince  :idea:

[Annie]

Sounds like acrab apple to me too,when are the fruit on it and what colour?