I’m new to Apple growing (3 Cummins trees, Liberty, Freedom, Williams’ Pride, all in 3rd year on semi-dwarf rootstock), so apologies if this is a basic question. As I was getting the trees ready for winter I noticed something odd at the base of one of them. See pictures below. It’s a bulge in the trunk near the original graft union. I was thinking maybe crown gall, but it doesn’t really look like other pictures I can find of crown gall. It normally has a white spiral-wrap trunk guard around it, which I moved up for the picture. Am I looking at a burr knot here? It does have some roots growing off of it, but is pretty smooth in parts as well.
Looks like a burr knot to me. Also, your landscape fabric or whatever that is too close to the trunk.
What exactly is the rootstock? MM111 makes burr knots a lot.
I had growths like that on quite a few of my apple trees that I kept the white spiral plastic on for over a year. Sort of looked like knobby knees. After discussing with others, I removed the plastic and filed down some of the growth earlier in the summer. I ended up whitewashing the trunks instead. It happened in all 5 trees that were wrapped, so Im sure that is the common denominator.
Thanks for the advice! I was wondering if the spiral-bound wrap was problematic because it does have sharp edges. This gives me an excuse to whitewash.
@ribs1 I’ll back the landscape fabric off all 3 trees. I haven’t mulched there, only had the fabric with stone over it. Do you suggest keeping the stone away as well? In spring I’ve been pulling the fabric/stone away to spread compost around the base (away from trunk), then re-laying the fabric/stone.
I have the same problem on a couple of the trees that I have used spiral wrap on. I very likely left it on too long. Last two trees that spiral wrap was not used on, do not have that problem. Most are on G11.
I have seen the burr knots on some of my trees as well. I will have to re-examine what rootstocks seem affected, I used the white spiral guards on them and the vast majority of my trees no not have the burr knot issue. So I would have to question the part about the white spiral guards being an issue. At least at my location. I would also think the issue may be with certain apple varieties.
@MikeC, I may be totally wrong, but history leads me in that direction. Some of the burr knots even have a twist to them that could be the result of a spiral cover. Maybe it is the rootstock, unsure?
True, I am not sure if the spiral covers make a difference. If they did I would think all my apple trees would have them since I used them on all of mine. I will take an inventory here in the spring to see what is and is not affected with burr knot. There are not too many I have that have gotten burr knot. Plus did I plant them too deep, not deep enough, etc…
