I grow many plants in hypertufa pots and I find them to grow amazingly well. Perhaps it's the lime in the portland and the natural soil additives of peat moss and perlite. Anyway, I do herb dish gardens and my friends are amazed at how well they do and I sell many of them. Go for it!

lf, your project is feasible. It's no problem to plant anything in hypertufa. The lime will eventual wash out between watering and rain. Very few plants are that sensitize to the lime. It depends on the wood. Throw some planks up, nail the ends together, drive in support stakes along the sides, back fill with soil and your done. Billie