Harry Harrington covers wound sealing on bonsai, rarely using sealants in 30 years except for resinous species like pines and junipers. For others, he applies putty and covers it with foil to block sunlight, protect from slugs, and speed callus formation. Large wounds heal in three to four years.
Chapters
Some of you will know already that I don't bother to use any wound sealants when making large wounds on my bonsai. Actual dieback from a large wound is very, very rare. In fact, I can't think of an instance where I've created a wound that's died back in nearly 30 years of doing bonsai. Where I do use something to seal a wound is on resinous species like Pines, juniper, or spruce, where a thin layer of Vaseline is enough to stop the, the wound bleeding. The tree I'm working on here is an acer palmatum, and it's midsummer. I've just created the wound, and this is the best time to create a large wound because callus formation is very quick anyway. However, with some species such as beech and acer palmatum, it is kind of expected as trees that do callus well anyway. That there's a full callus over the entire wound, and this can take several years to actually form. This is where wound sealants do come into their own, because callus formation is always stronger when you protect the callus itself from the sunlight. And then an opaque wound sealant over the wound, specifically the cambium layer, will really speed up callus formation. Now, this is a little trick I've been using in recent years, is to cover the, the wound with a putty wound sealant, and this will block out a lot of light, but a layer of foil over the top blocks out even more light. So the putty's gone on here, the— on this newly made wound. The cambium layer will naturally be healing itself anyway, but I want to really get that callus formation. So a small square of foil is cut and it's placed over the top of the wound sealant. The wound sealant's great for actually holding that foil in place, and it will protect the The wound sealant from being eaten by snails and slugs. The foil is also really good to just form around the, the trunk and stay steadily in place. I estimate a wound of this size to take around 3 to 4 years to heal over completely. Much depends on how quick I can get the tree to grow. And then of course the foil and wound sealant can be removed. And if you look at the trunk from the front of the tree, you can see what I'm trying to aim for— a nice healing over and a nice smooth transition between the lower trunk and the upper trunk.
