Mailbox Planter - with clay or without??

[mrbingos]

:) Hi y'all - I just built a brick mail box planter with drainage holes, and was wondering if I should treat it like a pot, ie: not mixing clay in the garden soil, or should I add my Texas black clay in the garden soil mix?

(The foundation of the planter is cement, which we added after teens knocked over our brick mailbox pillar, and I plan to add large rock gravel in the bottom for better drainage.) Thanks for your help! :)

[sandih]

I wouldn't put clay back in a planter box. Use a good quality potting soil with lots of compost.