As soon as it is in the ground it will grow much much faster. It will grow to about 50-60 foot - so ensure it is 30 foot from your (or anybody elses!) house - because the roots will probably reach that far. Other plants will suffer from lack of moisture under it too. Also think about what the view will be from any windows near it - you don't want to block all the light out of a room in twenty years time. It is always worth putting a lot of thought into where a large tree is planted. It can cause problems with neighbours and/or the sale of your house if you don't. If you decide your garden is not big enough why not donate it to a local school, park or old peoples home, that way you and others get to appreciate its lovely shape and form over the years.