Growth on Victoria Plum tree

I have a Victoria Plum in a pot on the patio, it is in good health, provided first plums last year and is carrying plenty of young plums now.  However, it seems to have a thick stubby growth developing - not like a new shoot, but like a wart on the side of the tree.  Does anyone know what this is and how to deal with it?  

Hi Tony,

If they are definitely attached to the trunk, it could be a type of fungus (probably a young bracket fungus which hasn't opened yet, like Phellinus pomaceus, common on plums) but these generally only affect old or stressed trees.  If it is that, I'm not sure what you can do other than cut them off and keep the tree well fed and watered.  It might kill the tree eventually, but that could take many years.  If they are woody, it might just be the trees reaction to damage or a canker.  Personally, I'd take a sharp knife to it. 

Thank you bob,i thought i,d cut it off but was,nt sure.What is a canker exactly? Its a shame because the tree is young flowered very well and carries lots of small friuts,i;d hate to lose it.

Cankers are caused by fungi or bacteria.  Basically, the tree grows a lump around the infection in an attempt to control it.  As the tree is otherwise healthy, keep feeding it and it may well recover or at least last for several more years.  Good luck with it Tony!