Roots of growing plants competing for water resources

If you’ve got perennial or shrub-like plants in your windowbox, such as soft fruit bushes, there is no harm digging up the plants at the end of the season to chop back some of the roots and pruning the stems (a bit like bonsai, but not so extreme). This is also a good time to replenish the compost, which will probably need bulking up again with more fibrous, nutritious matter.

Mintmulch
Lemonbalmmulch

 Water loss through plant leaves, particularly on hot or windy days

Try and pack in your plants (within reason), with taller plants at the back, graduating to shorter plants at the front. This will help protect the taller plants from strong winds and also create areas sheltered from the direct sun and wind. Grouping plants together also increases the humidity around the plants – all of which helps to reduce overall water loss. You could also drench leaves from above on hot days (out of direct sun though)