Paint the entire shoe rack with an exterior wood varnish to seal the wood and protect it from the elements. Let the varnish dry for at least two hours.
Sand away any imperfections with 250-grit sandpaper and apply another coat of varnish. Let this coat dry overnight.
Set the shoe rack in the spot on the patio or balcony that gets the most direct, unfiltered sunlight.
Set one rectangular planter on each level of the shoe rack.
Direct-seed plants for the shoe rack in the spring or start the herbs inside during the winter and transplant in the spring. With the herbs in pots, frost damage is less of a concern than when they are grown on the ground.
Water the shoe rack herb garden whenever the top inch of soil feels dry or if the herbs begin to wilt. Avoid over-watering as the water will spill out from the bottom of the planters and onto the rack, leaving water stains.
Trim fresh herbs whenever you need them for recipes. If a specific herb is growing too large for the container, trim it back and dry the leaves in the kitchen.
Change the soil in the shoe rack planters after the herbs die back in the fall. This way you'll have fresh, nutrient-rich soil for the next season.