Grape/Maple bleeding

My understanding is that if large cuts are made in the late winter/spring on grapes in particular they may literally bleed to death. Is there a technique or sealant that will allow this type of work at times other than fall?

Interesting question @SekiBonsai
I can only guess at an answer.
When I have cut Japanese Maple at the wrong time, the sap flows fairy quickly from the time of cut. I only cut small twigs, but was worried enough to use liquid cut past to seal.
I also know that petroleum jelly can stop sap on a pine
Looking at grape vines, I have often seen a waxy seal applied to cuts.
It’s almost as if the sap in vines and maples is under pressure?
Potentially, could a wound be cauterise with a hot blade? I have no idea.

You do not say where you are. Timing is important…
(Just my understanding…) after freezing in late Fall/winter, heavy trim the grapevine… ( maples too… ever collect maple syrup sap?) The liquid cut seal is a good choice, if you feel the need. Small trees might use up all of their resources…? Note: cut to a bud or two…
Commercial Grape vine trimmers use nothing. They take the vine back to the main limbs every year., and then re-tie vines for maximum production.
.BTW… kiwi vines bleed in spring. Do them as above , too. Ya, its under crazy pressure…
Cut seal…?
Note : The grape vine workshop at the 2018 Portland Bonsai meet heavily pruned in September with no sap bleed…
Hope this helps.
Hot knife…no.:roll_eyes:

The friend I am helping is in the Philly PA area. I am in TX…

May not strictly apply to bonsai, but we farm 31K vines for our wine production. We expect sap bleeding from fresh cuts when weather heats up. With vines in the ground, this is not a problem at all and may contribute to slight (desirable) devigorizing. With my bonsai grape vines, I do the pruning in the dead of winter (January in Oregon) before sap flow begins. The wounds heal without cut paste and don’t bleed. Our vineyard vines generally start pushing buds (become active) in mid to late March, sometimes as late as mid-April. Advice: prune early to avoid the spring flush of water and nutrients…but wait until fully dormant (after hard freeze) to avoid removing beneficial carbohydrates that are moving back into the vascular system.