Doesn’t the forest have to be already growing to offset my emissions?
That is correct; forests absorb CO^₂ during their periods of growth and a newly planted forest will obviously take some time to get going. Therefore if you wish to offset your emissions within a year, forest has to be planted a few years previously. This is precisely what Trees for Travel has done so that their customers can ‘hire’ a part of that forest in order to offset their CO^₂ emissions. This procedure is verified by both a certification organisation and a bank. Trees for Travel’s partner organisations use the income to plant extra forest, which can be ‘hired’ out in the future.  This results in more and more forest being planted that absorbs more and more CO^₂. This approach can be compared to the work of an emergency aid organisation; after a disaster, money is raised for tents, blankets and food. In reality, these supplies have already been purchased and stored in a warehouse by the aid organisation, ready to be dispatched immediately to the disaster zone. The donations are actually used to buy new emergency supplies that can be used for the following disaster. The replanted forests can be likened to Trees for Travel’s warehouse; while the disaster is the greenhouse effect.