Lacking a persimmon rootstock, you can graft a scion directly on a piece of root. Warm temperature is more important than grafting technique.
This spring I gave away a persimmon sapling I had propagated by bud-grafting Fuyu persimmon onto American persimmon seedling rootstock. In the course of digging it out, some root ends got left in the bottom of the hole, Before I filled in the hole, I reached down and grubbed out what roots I could.
I had three healthy pieces of root, and decided to try an experiment, grafting directly on to them.
Grafting a twig scion onto a section of root is an old technique. It is not so popular in modern times for various reasons.
- Nowadays, nursery rootstocks are generally available, having stem caliper the right size for grafting to twig-sized scions.
- Grafting two twigs together (the scion, and the above-ground section of a rootstock whip) is more straightforward, and easier to mass-produce, than fussing with irregular roots.
- Since the graft is below ground, you have to dig down later to remove the wrapping.
- It wouldn’t work for dwarfing rootstock unless you either jacked the graft up to expose the top of the root, or were satisfied your stock were going to merely act as a nurse roots till the scion grew its own, and you had essentially rooted a cutting.
Still, it’s useful to know this is an option. Sometimes, rootstocks are hard to come by, and it’s worth the extra fussing. It’s easy to buy rootstocks in quantities of hundreds from commercial nurseries. But if you only need one, nobody wants to deal with you.
I matched the root sections by diameter to dormant persimmon twigs.
I joined them by whip-and-tongue grafts.
I wrapped the unions shrink-fit-tight in black electrical tape, my standard wrap for dormant wood grafting. I did the grafts on March 4.
Grafts heal because a tissue called “callus” grows out of the exposed edges of the cambium, and fills in gaps like hot-melt glue. This is somewhat analogous to the healing of broken bones, where a knot forms at the fracture, and then gradually turns into normal bone.
Easy-to-graft species like apples and pears have callus that grows at winter temperatures. By the time the scion is ready to leaf out, the graft is healed, and so it grows. However, other species are difficult because their callus needs higher temperatures, typically at least 25°C (77°F), to grow. By the time the weather gets warm, the scions have shriveled up and died. This difficult category includes nut trees and persimmons.
The Oregon filbert industry relies on a technique called “hot-callusing” to propagate nursery trees. Filbert scion twigs are grafted on rootstocks in winter, when everything is dormant. The weather is too cold for these grafts to heal on their own, but the hot-callus technique is to lay out these across a heat pipe to keep the graft union warm. Example here.
This is fine for a nursery operation, but a lot to set up for merely a few grafts. You can fake it by keeping the whole graft warm. This is a trade off. The graft union gets the warmth it needs, but the roots can shrivel and the top can start to leaf out and lose moisture.
I did the best with what I had. I put the root ends in damp sawdust to stay moist. I enclosed the whole business in a produce bag to retain moisture.
For warmth, I put the setup in my propagation chamber with the tomato starts, about 27°C (81°F).
I got around to checking the grafts on April 21.
One had completely dried out and died.
One, the graft had died, but the root had put up adventitious shoots.
One, in addition to adventitious shoots, was budding out from the scion.
This shows that persimmon root grafts work, to a certain percent, even with slapdash technique, as long as you keep them warm.
I offered the grafted tree as a giveaway, but did not have any takers. I had no place to grow another persimmon tree, so I let it dry up and die.
Rick Shory 