Is this root or trunk on my Asian persimmon!?

[Mossy Dell]

I have a question about what is upper graft wood, and part of the trunk, and what is root on an Asian persimmon. I got this potted plant mail order this summer. The grafted sapling's trunk came straight out of the pot, no root flare. Leaves became yellowish, and I gave it some Fertilome Root Stimulator, very low Nitrogen, Phosphorus, and Potash. It had little response, though all other struggling plants have really responded.

THEN I re-potted it in a bigger pot, to grow more till fall. This revealed a buried 3"+ section of much darker wood and then a slight flare and roots. That's the graft wood, I thought. There were no roots coming from the black formerly buried trunk part. I potted it with that black wood out of the ground. The leaves stayed yellowish. I gave it more Fertilome to little effect. The yellow leaves may be a completely separate issue, of course.

Yesterday, I planted this tree out. I split the difference, burying about 1"+ of the dark graft wood, as it seems to me. There were no roots coming from the dark wood, more support for a trunk that got planted too deep. But again, it stayed black and it and the tree did not change after 2+ months above ground.

The picture shows the black trunk base and the clear line between the bottom black part, which I think is the graft, and the lighter brown trunk. I can bring in some more soil if the black should be buried. Or I can lift it if more of the black should be out of the ground. I have written the nursery but have gotten no response yet. Help!
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[Chuck]

The black part is the after effects of being planted too deep. The graft union is that slightly larger diameter part slightly above the soil level. The tree is still planted too deep as the root flare is not exposed. That black color is not a good sign. I would drench the soil and the blackened part with 1/2 cup of 3% hydrogen peroxide per gallon of water in hopes of stopping that black fungal growth.

 

[Mossy Dell]

The black part is the after effects of being planted too deep. The graft union is that slightly larger diameter part slightly above the soil level. The tree is still planted too deep as the root flare is not exposed. That black color is not a good sign. I would drench the soil and the blackened part with 1/2 cup of 3% hydrogen peroxide per gallon of water in hopes of stopping that black fungal growth.

Thanks so much, Chuck. That was my sense when I uncovered it. But it was sent by Stark Bros and I thought they'd know what they were doing. Fact is, the probably bought it from a grower.

I will lift it tomorrow!

 

[Mossy Dell]

Oh, and I'll try the hydrogen peroxide treatment too. Great suggestion, Chuck, great information. I bet that's why this tree has been struggling. Makes me think I may be too late to save it. But I'll try.

 

[Marck]

Whether to bury or expose a graft union can be a contentious issue, though in some cases either option can give good results. This seems to be the case with the Asian Persimmon (Diospyros kaki), so you may have good results with the grafteither buried or exposed, though local soil and climate conditions could change that.

Overall for all grafts, the decision to bury or expose at least partly depends on the reason the plant was grafted in the first place.

Many plants are only grafted because it is the easiest or most economical way to propagate them. For these types of plants, cuttings either root with great difficulty or grow too slowly, making propagation from cuttings not feasible for commercial production. Later at planting time, Some growers prefer to bury the graft union of these plants so that they will then produce roots directly from the scion. This may also prevent dieback to the graft union which can be a concern, especially in colder climates. Rosa and Paeonia grafts are often treated this way. Also some growers of roses and peonies have now mastered cutting propagation to the point where grafts are no longer needed.

Other times, a plant is grafted partly for the characteristics of the rootstock, which may be either a selected cultivar or an entirely different species. In this case burying the rootstock often is not recommended because the benefits of the rootstock may be lost or compromised. Such rootstocks can deliver either increased size or dwarfing, increase growth so trees fruit younger, or give greater tolerance for different soil types. For example some fruit tree species have different recommended rootstocks for sandy soil vs. clay soil.

In the specific case of Asian persimmons (Diospyros kaki) grafting seems to be done mostly for propagation reasons, though different types of rootstock can affect the scion differently. Diospyros kaki seedlings can be used for the rootstock, though currently the Date Plum (D. lotus) is the most popular rootstock, partly due to seed availability. American Persimmon (D. virginiana) is also sometimes used.
Which one of these species makes the best rootstock seems to be another subject of debate among fruit growers, and the answer may depend on the scion cultivar.

By the way, Diospyros lotus and D. virginiana are also interesting fruit trees worth growing, though the fruit is smaller than that of D. kaki.

Also, the buried part of trunk will usually be darker due to staining by humic compounds in the soil. It is not clear to me from your picture and description that there is any rot or fungal infection.