At the risk of being spoofed, I have to say your tree is fine. Yellow is the fall color for tridents. Your tree does need more sun than you are giving it, however. Timing on fall color depends largely on how the tree has been kept in its life, and it only slowly adapts to new conditions.

Chris

March is October down under and although Victoria isn't as harsh as some of OZ,(it rains at the MCG even) the trident may be suffering from a bit of heat/dryness stress which has prompted a scraggly look and what seems to be an early-ish leaf drop.

Also not so sure that the Mediterranean type climate you have there is suitable long term for tridents. For instance, acers in general seems to be a problem in Southern California

Tridents don't like to be kept particularly dry - a tad on the damp side is better in fact. I've had acer palmatum go into late summer heat shock and drop their leaves as early as August but come back next spring AOK.

Tridents are not particularly famous for spectacular leaf colour and display in fall although there are techniques to improve the display I believe.

I'd keep it slightly damp over winter and keep an eye on it.

Get worried if no buds start to show round August time or the small branches go all brittle and crispy.

Thanks for the advice. Comforting to hear that it doesn't seem to be serious. I'll speak to my local centre anyway. Can't be too careful, and I'd hate to lose it so quickly!

Geoff

It bears mentioning here that trident maples must be kept outside...