Hello UBC world, Has anyone experience of grafting black walnut rootstocks? I have excellent technical references to guide me but as local opinions go, can confirm that its not easy after two attempts with 50+ plants. Can anyone relate optimal timing with leaf-burst (eg. 2 weeks before etc) Thanks
Re: Garfting (black) walnuts Griffon, I do all my walnuts after the rootstocks have completely leafed out. I use, for most grafts, a technique similar to the 'sap-stopper modification of the Gray graft'. It's really just a simple bark graft, but rather than completely severing the rootstock, you cut 3/4-7/8 of the way through the stock, and break the top over, leaving it attached, so that it can serve as as 'sap-drawer' or 'pressure-relief valve' of sorts. Then, I make a vertical incision downward from the point where the rootstock was (mostly) beheaded, make a long, sloping cut in the basal portion of the scion - just as you would for a simple whip/splice graft - shave a little bit of the lateral edges to expose more cambium, gently lift the edges of the incision in the rootstock bark and slide the scion down into the slit. Have a look at my buddy Joe's bark grafting tutorial here: http://citrus.forumup.org/about500-citrus.html This is how I do them - with the added incorporation of leaving the top attached & broken over. Once the graft is callused and growing well, I'll come back and cut off the broken-over top of the rootstock. Walnuts tend to bleed excessively, and you either need to use this technique, or cut off the rootstock at whatever height you intend to make your graft - and then wait until they stop bleeding(may take as many as 7-10 days, sometimes) to make your graft.
Lucky, thats valuable info thanks! I haven't come across this method before. If my comprehension is correct, choice of scion (rather than bud) makes material less vulnerable later timing (than 'winter') ensures the rootstock is truly active ... and temperatures will be higher (important for walnuts). I presume that scion material must be refrigerated, as for earlier methods. I'm interested to note how much protective wrapping is specified in the tutorial; firstly for mechanical reasons, then anti moisture loss. For the latter, I have thought of using a small poly or selophane bag; is there a reason why this might not work? Otherwise, I'm fascinated to note difference in opinions as to where the cambium resides after rootstock prep cuts; critical to your scion prep detailing. Moderators; tried to edit my typo in the title. Can this be changed?!
Re: Garfting (black) walnuts Griffon I wrap with Parafilm, as Joe did - starting at the bottom and moving up - but I wrap the entire scion(I usually try to use a 2 or 3-bud stick, but have used 1-bud pieces when I've had extremely limited material. Then, I wrap with a budding rubber - but I start at the bottom and wrap up - then back down again, if I have a long enough rubber. I collect dormant scionwood in Feb/early March, and keep it refrigerated until ready to use. I suppose a plastic bag over the top of the graft might work OK to control/maintain humidity. Come to think of it, I think one of my friends in MI uses a plastic bag - and a brown paper lunchbag over that.
