Can I expect good results growing pecans in heavy clay soil where there’s temporary floods in september/october during heavy rain periods? Topsoil is quite rich in humus, then it’s red clay that holds tons of moisture during the fall. I’m not sure if pecans would thrive in such conditions or would they have issues with it. In the summer moisture levels are normal and there’s no standing water.
So I have three choices how to plant pecans in such conditions:
Red clay is not a major problem. I have pecans here at my house planted on top of red clay. Gray clay generally is impermeable to water and air so is not suitable. Pecan is relatively tolerant of short term flooding but would be better if they’re planted in a mound of topsoil at least a foot higher than the surrounding area.
Just adding to the thoughts, red clay is from air penetration of a clay soil with iron content. The iron can benefit pecans quite a bit. However, clay soils often don’t have enough zinc or nickel so do a soil test and find out what is recommended for supplements.
And there’s another place where there’s too little moisture (upland). From what I’ve read, I would expect pecans to do worse there (without irrigation). I’ve heard that shagbark hickories prefer upland. But… what if it’s grafted on a pecan? The roots would still be pecan’s, that are not the best for dry soils, does it make a difference?
Would Shagbark Hickories or Persian Walnuts or other nuts grow there better?
You ask a great question wondering about rootstock such as pecan growing in an upland or otherwise unsuitable area for pecan trees, even though the roots are topworked to a species such as shagbark which is tolerant of some upland growing. I don’t have the answers to this, but have wondered the same things. I think there can be a lot of blind spots and unstudied aspects of nut culturing that need more examination. One of them is the assumption the pecan rootstock is always the most ideal rootstock for hickory. That might only be the case in bottomland/valley/fertile habitats, and further, some cultuvars might do better NOT on pecan. People observe pecans vigor and jump to the conclusion that therefore that means it makes the best rootstock, regardless of nutritional and genetic compatibility issues.
I think a good test study would be the old Benton & Smith nursery in Wassaic NY. The context for these trees (at least most of the remaining ones) is steep, rocky, acidic hills. As far as I know, most all of those hickory selections were grafted onto the wild shagbarks as rootstock, not planted out on pecan or even shellbark rootstock. Is this because they found that the bottomland rootstocks didn’t perform/suffered, or was it simply convenience? I don’t know for sure, but do know that now 75+ years later some of the trees are still alive and producing, so that counts for something.