In order for the graft to take, contact must occur between the cambium layer of the scion and the cambium layer of the rootstock. If this doesn't occur it leads to graft union failure.
|The contrast between a failed graft (top shoot) and a successful graft (bottom shoot).|
This photo series shows fail of the graft to make a union with between the cambium layer of the graft (scion) and the host vine (rootstock). Symptoms of this are sudden wilting of the grafted bud and also shifting of the union under the grafting tape. Prior to the the graft bud developed normally and was 7-10cm long.
|Callus is the white tissue that forms on cut surfaces.|
Note that there is only a very thin line of callus tissue linking the graft to the rootstock. When the graft is unwrapped it easily slips out.
Unfortunately, the graft union has ceased to take. When this happens, the flow of nutrients from the rootstock to the top growth (scion) stops completely and the top growth will deteriorate.
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