You can still graft onto rootstocks that have come out of dormancy as long
as the scions are still dormant. If the rootstocks have gone too long
without any buds leafing out though it can lower your chances of success,
in my experience, if I recall. If you whip and tongue grafted earlier you
can do another whip and tongue graft lower on those that didn't take but it
would be much better to use new rootstocks. You can also chip bud using
dormant scions but my experience has been weak after- growth. I don't like
re- grafting the same rootstocks in the same year, but I have done it with
some success.
I have kept scions dormant at about 31 degrees up into June. (I have also
frozen them and kept them into July. Freezing them is very risky though,
you probably have to do it when they are in primary dormancy, in the late
fall, and freeze them in a large amount of water with no contact with air
or the sides of the container.)
As far as apple and pear and plum you can graft on dormant roots, apricots
and peach actually do better if the rootstock has begun growth. You can
even grow out some suckers from the peach and apricot rootstocks and whip
graft them to your dormant scions, that is if you can keep your scions
dormant that long. You should protect the new apricot and peach grafts with
a plastic cover and slowly allow them to harden off once the grafts have
taken. Pears and apples will callus at low temps from the high thirites and
above, 50 degrees being ideal in my opinion. Apricots callus best in the
upper fifties and plums in the seventies. Peaches alos I believe in the
seventies and even eighties.
Good luck
Kevin B.