I was wondering how high everyone positions their graft union above the surface when planting. Here’s a photo of a graft I did in 2017, B118/Liberty. The tree is doing very well. Will this be an issue though. I always tried to keep the graft union a little bit above ground, in case it failed, so that I could have room for a bud graft. Thoughts?
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High enough that the scion does not start to root because it would nullify the rootstock it is growing on.
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Looks good.
I grow on M7 rootstock and have had a rash of Burr Knot. So in my most recent plantings, I buried right up to the graft union. Of course it just struck me within the past few days why I have an outbreak of burr knot. I protect my apple trunks the same way you do, and the darkness and moisture under the pipe creates the right environment for rooting. I’ll be protecting my “above ground” rootstocks differently next year.
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They always told me, “About 4”…" But they also told me to mulch my apple trees. I believe now this is contradictory. Mulching raises the ground level and with time may bury the graft union unless you leave a 4" deep depression around the trunk. I try not to make any such effort and use plastic mulch instead. You may wish to consider using organic mulch and therefore set the graft union much higher — perhaps 8" or more above grade at time of planting. I doubt that this has any implications for suckering or strength of the union or cold tolerance of the root stock, but I could be wrong.
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That’s a lot of mulching to create a 4" deep humus layer. In the humid regions it’s probably best to lay off the mulch after trees are established in most soils, at least on free-standing root stocks. Nothing contains more available water than pure humus and that reservoir may be welcome during droughts, but on normal rain years it can bring down brix of fruit some.
I don’t think scion rooting is as common as the literature suggests- depends on the variety and certainly N.Spy, Gala and other ones that have burr knots on bark would be likely to root out if exposed to soil, but I’m not at all sure that the majority of varieties would. I’ve seen commercial orchards where trees were planted too deep without any symptoms of excessive vigor.
Of course, varieties vary a great deal on vigor anyway. I doubt a Goldrush on 111 would be affected at all if the scion rooted- I think it would still put most of its energy in fruit production.
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