Cold Hardiness of Different Bombacaceae as Rootstock

[Loxahatchee Adam]

With it being Floss Silk season, I've been going around finding trees with unique flowers and either getting cuttings for grafting or marking them down for later.   In the past, I've successfully grafted Floss Silk onto Ceiba pentadra (Kapok), Ceiba speciosa (or whatever hybrid of floss silks it is), and onto Pachira aquatica.   I'm going to plant several around a lake here that occasionally floods, which is why I've been grafting some onto Pachira aquatica...they can go completely inundated several feet over the ground and are fine.   I have one planted in a seasonal flooded area and it shoots out pneumatophores from the trunk.  Kapok trees also have much more flood tolerance than Floss Silks, but not to the degree of Pachira aquatica.

For the dryer areas, there is more flexibility for rootstock Kapok vs Floss Silk....just what seedlings I have large enough for rootstock at the time.    I live in current zone 10a, old 9b, in far western Loxahatchee.     My preference for some areas would be Kapok as rootstock vs Floss Silk, as they handle wet better and are less spiny (horse/people areas).  Sometimes the cohesive spiny trunk looks better though.   My concern is- I don't want to use Kapok if they may end up being less cold-hardy during a future freeze event.  Usually the concern is freezeback above the graft and the rootstock turning into the new tree. For this, if the rootstock dies, then the top of course goes with it.  

Do any of you have experience with Kapok and Floss Silk of a similar size and in the same weather conditions going through a freeze event to compare?  I've looked back through old freeze damage reports on here, but there's no way to know if they are fresh 3 gal plants or 25 ft tall to compare.

 

[fastfeat]

Interesting and likely useful choice of Pachira aquatica esp. for Florida. Might consider P. glabra ("good-luck/moneyplant") as well. Probably more cold-tolerant and smaller species that might add dwarfing characteristics.

In CA, C. speciosa is used as a rootstock for select cvs. and also for Bombax ceiba.