As requested by a little mathematician I put the corresponding subtraction sum on the back of each tree.
Pieces were stored in a little tray with small pieces contained in an empty Branston pickle and cheese snack pot. The counting decorations were mini craft gems and sequins (without sticky backs)
The activity was a real hit and so good for fine motor control, counting those tiny gems on to the trees which had a terrible incline to slip rather frustratingly at times. We ended up doing on a try in the end as carpet made the trees quite wobbly, I think I would use thicker card, laminate or use felt if I were to do it again.
Remember, learning should always be tailored to the individual needs of the child. Addition and subtraction should not be attempted until the child is confident in counting with one to one correspondence, has lots of experience or dealing with numbers in everyday activity, has experience of language such as one more, lots more, take one away etc. in everyday activities and through songs. The child can then begin to deal with problems in play and everyday activity e.g. "We've eaten two biscuits how many are left?" Only when a child is confident with such "problems" can addition and subtraction in this way even be contemplated.
For a printable version of this activity go to TES simply register for free and you can down load for free http://www.tes.co.uk/teaching-resource/Christmas-Tree-Addition-6066768/requestAction/update/