Next, determine the look you want. Formal or informal? Formal herb gardens are based on patterns and geometric shapes-squares or rectangles, for example-that are divided into smaller, mirror-imaged beds, which are almost always enclosed by low hedges and dissected by paths. Small, compact herbs are usually chosen over tall, showier varieties, and in some cases, entire beds are devoted to a single herb. Formal herb gardens, although beautiful, can be labour-intensive; there are hedges to trim, paths to maintain and beds that must be weed-free to look their best. They can also be expensive to install.
Informal herb gardens are simpler to maintain. Avoid straight lines, squares or rectangles; aim for loose, irregular and adaptable shapes. Informal gardens appear in many guises, including sunny flower borders, shady woodland plots or dry Mediterranean rockeries. Small installations can be tucked into a corner by your front door just as easily as they can be planted in your vegetable garden, and look as pretty in the early stages as when fully mature.
Whatever the garden style, you'll need paths for easy access. These should be between 45 and 60 centimetres wide-double that if two people want to stroll the garden side by side.
Divide the plants from the path with a 15- to 30-centimetre-high edging of brick, wood or stone. Edges also help keep the garden looking tidy even when it needs weeding. Or install a soft border, such as lavender, santolina, dwarf box or germander, keeping in mind how big the plants will be at maturity and that they'll require regular pruning.
Though many herbs are drought-tolerant, it's important to water them regularly while they're becoming established and at the start of each season when they're putting on new growth. Moisture requirements vary from herb to herb, so water at the base of the plant to give each exactly what it needs.
Herbs are relatively resistant to pests and diseases but are not immune to attack. Avoid problems by maintaining healthy soil, raising or buying robust seedlings, properly hardening off plants before planting out and adequately spacing them to encourage air circulation.
Pests to watch out for include slugs, which adore many herb seedlings. Hand-picking at night is the best control. Aphids, whiteflies and spider mites are more often found on herbs grown indoors, but will attack tender outdoor herbs, especially nasturtium, calendula, lemon verbena and scented geraniums. Squashing them by hand or blasting them repeatedly with water usually dispatches them.