A tree who gets a longitudinal cut through the bark and sap wood will heal it through overgrowing from the sides,, since the scar cannot grow new cambium and bark.
Overgrowth takes place from both sides and the resulting wood is called svallved. It s thick cell walls make it very hard and strong and it have been used for ax- and hammer handles, rake heads, ski poles and more. It is mostly used north of Dalälven, where hardwoods as ash, oak and elm do not commonly grow.
You can make svallved by making a longitudinal, fairly wide cut in a trunk, preferably a birch. 20 – 30 years are needed to produce svallved suitable for ax handles.
In the old days it was common practice to regularly prepare svallved for future use. Today it is mostly caused by browsing animals or by forestry vehicles.