Zinsser Bulls Eye Shellac makes a great pruning sealer

Bulls Eye Shellac is an alcohol-based solution of lac, a natural resin. Dries transparent with a faint, golden cast that is much lighter than oil-base varnishes. Offers many advantages over other clear finishes: it's easy to use, dries quickly, is non-toxic when dry and cleans up easily with ammonia and water.

Great for sealing on trees or where you have pruned limbs.