IMHO they will probable be fine, but I haven't had to prune large branches. My maples (Sugar, Freeman, etc.) all "bleed" allot more than you would expect, but it doesn't seem to harm them. Still if I were you I would not prune any more off.

Arktrees

Hopefully the tree will be alright but wounds take a long time to heal in the early spring, and it may continue to bleed for some time. As you have found out, the sap is already rising, and as far as the tree is concerned it is no longer the dormant season.

There is not much you can do at this time, certainly don't try to seal the cut with anything.

For future reference, I would limit pruning to before the new year, November and December would be good months to choose.

FYI, if you are in a mild climate as I am here, it does not matter when you prune, they will still "bleed" anytime the temp goes up a bit. I did some pruning earlier in the season, then the ground froze, and when the temp rose to a few degrees above freezing, the "bleeding" began again even thought the ground was frozen solid on the surface. So ikea_gw it almost certainly does not matter when you prune in the winter. The key is just don't over do it. You may prune on or two limbs, wait till the "bleeding" stops on warmer days, then prune one or two more. Also probable better if you prune at the start of a few cold days.

JMHO
Arktrees

I'd think you prune shortly after the plant defoliates.

I never experienced bleeding on my maples as I only prune in summer or mid/late fall.

I agree with whaas, it is better to prune when the sap is falling. By the time the sap starts rising again the wound will be at least partially healed to a state where very little (or no) sap leaks out.

Btw I am talking about Japanese maples, I have no experience of Sugar or Freeman maples, these might be different.

So all the books I read about winter pruning Japanese maple are all wrong? It is the coldest time of the year for us here.

As previously stated, in our very mild PNW climate it is not uncommon for JM's to have early sap activity - the rule of thumb is to prune in December/January but that's not always a guarantee that you're going to miss sap bleeding.

I prefer to prune in summer - June is the ideal time. No sap issues and I find it easier to determine what to remove. Dead wood is very obvious and it is clearer what branches to remove to thin or lighten the canopy. I tend not remove any lower branches unless they have been damaged or are somehow conflicting - low branching is one of the characteristics and attributes of many cultivars of JM's and they tend to be attributes I'd prefer to maintain.

Cass Turnbull, the founder of PlantAmnesty and perhaps one of the most skilled and knowledgeable arborists/pruners I've yet to meet has written a very good, concise article on the subject for Fine Gardening, attached below. It is very much worth reading.

Here is a link that might be useful: Pruning Japanese maples

My experience is with the Sugar, Silver, Red and its cultivars.

Like gardengal, I do much of my pruning in June. Many question it but it works out for the better. Late October is my other time frame when I need a better picture of the interior branching structure. Again I took off limbs the size of my head and no bleeding occurred.

I don't understand why you'd prune in Jan for a milder climate. Why not after the plant defoliates?

The old timers used to say, "Prune bleeders ( maples, birch, sweet gum and so forth ) when night temperatures stay above 50 degrees" In my area, that would be April-ish, usually. They were also referring to light, thinning cuts, not major surgery.

On the other hand, people have been punching holes into sugar maples every winter for hundreds of years, so I've also assumed that sap flow per se cannot be too detrimental....

brian

I just pruned two freemanii maples with the temperature here at 40 degrees for the high. They bled profusely, so obviously they are pushing sap. This is the first pruning for these maples after five years in the ground. I, too, read that early winter would be a good time to prune and avoid bleeding...NOT SO, even though it's cold out there. It doesn't feel right to prune when trees are in leaf (mostly because that's when I want to look at and admire them), so next time I'll prune right after leaf drop.

Where is everyone getting this info? I read that late summer, early fall, early winter, late winter and early spring are the times NOT to prune Maples.

Prune early summer, late summer or late fall. No one should be able to argue this.

Well techincally you can prune a maple at anytime.

You can of course prune a maple at any time, even when the sap is rising. The 'bleeding' of sap is more of an issue for the one pruning rather than the tree - it can be rather startling just by quantity but it is not harmful to the tree. Reports or rumors of maples "bleeding to death" are alarmist and untrue. Early to midwinter is a recommended time - generally the sap has descended and is not active at that time, but it does depend somewhat on location and climate. To avoid any bleeding sap issues, prune in late spring or early summer after foliage elongation. Even immediately after leaf drop is not ideal - pruning stimulates growth and if the tree is not well into dormancy, mild temperatures at that time could encourage a flush of new growth that can be damaged with cold.

Often a combination of pruning times works best - light pruning during early dormancy when it is easiest to see the tree form without leaves and a harder pruning late spring/early summer to lighten the canopy or remove major limbs.