Vertical planting challenge

The herb wall we planned was much anticipated, but it needs irrigation to really hit the mark.

The plan for the wall here was a herb wall - a deep green haven for bees and a plentiful supply of herbs for the cafe. However, the posts are small and not retaining water enough despite having troughs within the pots. We’re not sure what will grow here without an irrigation system. Any ideas for what plants love dry soil?

MINT, OREGANO, CHIVES AND BASIL FOR THE CAFE

The herbs are wilting after a day, only the woody herbs like rosemary and thyme are surviving the heat of the balcony. Any ideas of how to retain the moisture in the soil?