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G'day Martin,
You make it hard old mate, where are you, what type of
maple, and where are the maples; in individual pots, separate pots, or all
in one seed bed? My guess is your talking about Jap maples (Acer Palmatum),
or mountain maples as the Japs would call them.
If you want to force the maples on, then plant them in
the ground (after root pruning), and feed and water like mad. You will get
much quicker growth (not that Maples are ever quick), and once the cold
winter drives them dormant you can lift them, pot them, and graft them next
spring. You can even graft them while in the ground, and even give them
another season in the ground to grow on. You will not need much room, as you
can pack them in like onions if you know they will be lifted and root pruned
next season.

China
Wingham
NSW