Why coastal gardens suit Mediterranean herbs

If you garden within sight or sound of the sea, you already know that some plants sulk. Delphiniums flop, roses battle blackspot and anything that craves rich, damp soil looks thoroughly miserable by August. Herbs are the happy exception. Rosemary, thyme and sage all come from rocky hillsides where the sun beats down, rain drains away within minutes and the wind never quite stops. That is not a bad description of a seaside patio, which is exactly why these three thrive in containers by the coast.

There is one catch, and it is the salt. Windborne salt burns tender leaves and dries compost faster than inland conditions ever would, so the trick is to work with the coast rather than against it. Choose the right plants, plant them in gritty, free-draining compost, and resist the instinct to water little and often.

Choose the right pot and compost

Drainage is everything. A herb sitting in soggy compost will rot at the crown long before drought ever troubles it, so start with a pot that takes drainage seriously. Terracotta is ideal because it is porous and lets roots breathe, but any container will do provided it has generous holes in the base. Aim for at least 30cm across for a single rosemary, and larger if you want to group plants together.

Stand every pot on feet, bricks or pebbles so water can escape freely. If you use saucers, empty them after rain. Then mix your compost:

• Two parts soil-based compost to one part horticultural grit for rosemary, which resents disturbance and likes a firm, lean root run.
• Equal parts multipurpose compost and grit for thyme and sage, which are a little more forgiving but still hate wet feet.
• A handful of slow-release fertiliser stirred through at planting time. Coastal herbs are not greedy, and overfeeding produces soft, flavourless leaves.
• A top-dressing of gravel across the surface. This keeps the collar of the plant dry, suppresses weeds and stops rain splashing soil onto the leaves.

If you can, raise the pot on a low wall or bench. Air moving underneath keeps the compost from staying saturated after a downpour.

Planting up and getting established

Plant in spring once the worst of the cold has passed, or in early autumn while the soil is still warm. Water the pot thoroughly, then leave it alone for a fortnight. New roots need to search for moisture, and a plant that is watered every day will simply build a shallow, lazy root system that collapses the first time you go away for a weekend.

Space plants so that air moves between them. Rosemary grows upright and can reach a metre in a good pot; thyme spreads and will happily trail over an edge; sage forms a bushy mound. Give each one room rather than cramming them together for instant effect, and pinch out the tips of thyme and sage after planting to encourage branching.

Watering and feeding without drowning the roots

The single most common mistake with coastal containers is kindness. Herbs from Mediterranean hillsides are adapted to drought, and a rosemary that is watered daily will yellow, drop leaves and eventually give up. Instead, water deeply but infrequently — soak the pot until water runs from the base, then wait until the top few centimetres of compost are genuinely dry before doing it again.

In a windy seaside spot that might mean every second or third day in high summer, and barely at all in spring and autumn. Push a finger into the compost, or lift the pot: a light pot needs water, a heavy one does not. Water in the morning so any splashes on the foliage dry before evening, which reduces the risk of fungal problems.

Feed sparingly. A dilute liquid seaweed or tomato feed once a month from May to August is plenty. Stronger feeding encourages lush growth that is soft, pale and low in the aromatic oils that give these herbs their punch. Stress, in moderation, is what makes them taste of something.

Wind, salt spray and shelter

Shelter matters more than anything except drainage. A rosemary in a gale will be stripped of leaves and battered into a tatty shape, and salt spray scorches tender new growth. Aim for a spot that gets six hours of sun and some protection from the prevailing wind — against a south-facing wall, beside a shed, or behind a low hedge or fence.

If your patio is fully exposed, group pots together so they shelter one another, and consider a woven or slatted screen rather than a solid one. Solid barriers create fierce turbulence on the sheltered side, which can do more damage than the wind itself. Rinse salt off the foliage with a can of fresh water after a storm, ideally in the evening so the leaves do not scorch in strong sun.

Harvesting and looking after them through winter

Pick little and often, taking no more than a third of any plant at once. Snip thyme and rosemary tips with scissors, and harvest sage leaves from the top of the stems to keep plants bushy. Regular cutting keeps herbs compact and productive, and flavour is at its best just before the plants flower — pinch out buds to extend the harvest.

Winter is when coastal containers are won or lost. Move pots against a warm wall, raise them clear of the ground, and cut back on water dramatically. Rosemary and sage will take a light frost if their roots stay dry, but thyme can be lost to a wet January far more easily than a cold one. Check drainage holes before the rain arrives, and resist mulching in autumn. Come March, a light trim and a fresh top-dressing of grit will set them up for another season of proper, pungent flavour.