What is this?
That is a £1 coin next to it, it is 10x7cms, 4x3 inches.



I grew it and it is the 2nd off the plant.

Is it a Banana?

Are you in shock or feeling smug you have managed to grow it? (I would be both)

Looks like a large lemon, or it could be a citron.

Neither shock or smug, simply puzzled.
The puzzlement is that it grew on a lime bush/tree I have indoors.

This image is another Lime that is on the same plant and actually was the same branch as the first they were about 2 inches apart until the big one fell off today.



There are several others and they are all lime sized limes, they look like limes and taste like limes. Have obtained a few from it most years.

This is the second big yellow one and assuming it follows the first when sliced the inside will be green and lots of lime juice.

This is the first year it has gone and produced "limes" that look like "lemons".

The colour is not a problem as to maintain "green" limes need tropical heat and humidity as otherwise the turn yellow. Have had a good number of small yellow limes, that tends to be normal. Just now I have big lemon looking limes, and that is not so normal.

Most citrus is grafted. Maybe it came from a branch growing from the root stock?

Very strange; there are lemon lime hybrids - I used to have one - but the fruits are intermediate, not either one thing or the other. Not rootstock because you would see the different branch (plus rootstocks tend to be either poncirus, or really weird and knobbly rough lemon type things). I understand in the US garden centres sell two-in-one-pot lemon and lime combinations, possibly with stems braided together. Could it be that?

Let us know what it's like on the inside.

Failing all else the nice people at the Citrus Centre are very knowledgeable.

Limes tend to be picked unripe when they're green. If allowed to ripen they do turn yellow naturally.