When do new fruit trees start growing I planted them last december
They are double Apple and pear
Certified GKH Gardening Expert
It really depends on the climate in your part of the world. Here in the US we plant both trees in spring so they have plenty of time to establish before winter. Not being able to establish before a freeze will certainly kill the trees. They will both show signs of growth very early in the year, usually.
These two articles will help: