Lisbon summer is unkind to herbs. Forty degrees, a south-facing balcony, two travellers who forget to water for ten days at a time. Our balcony has been a herb graveyard most years, but last summer three pots survived. The trick was not better attention. It was better species, the right pots, and a single idea about watering that I should have figured out years ago.

Why terracotta beats glazed

Glazed pots are pretty and waterlogged. Terracotta breathes. Excess water leaves through the walls, the soil dries evenly, the roots get oxygen. In a forty-degree week, glazed becomes a kettle. Terracotta becomes a damp cellar. Mediterranean herbs are cellar plants, not kettle plants.

Three terracotta pots in a row on a sunlit balcony, each with a bushy aromatic herb — rosemary on the left, bay in the centre, oregano on the right Save
Three pots, three survivors.

There is a tradeoff: terracotta needs watering more often than glazed. But more often than what — that is the question. The right answer is not a schedule. It is a finger.

What lived and what didn't

Survived: rosemary, oregano, bay laurel. Died: basil, parsley, coriander. Pattern: the woody Mediterranean herbs lived, the soft annuals died. Rosemary asked for water once a week. Oregano was indestructible — we found it leaning against the railing one morning and stood it back up; it grew. Bay laurel slow but steady; one good leaf a month, all summer.

Close-up of a thriving rosemary plant in terracotta with new shoots and a few woody stems, against the texture of Lisbon plaster Save
Rosemary, the easiest plant we have ever killed.
“Mediterranean herbs are cellar plants, not kettle plants.” — Mira
  • Rosemary, oregano, bay, thyme, sage — woody Mediterranean herbs survive heat and forgetting.
  • Basil, parsley, coriander, chervil — soft annuals need water every other day. We will not be growing them again.
  • One herb per pot, not three. Companion planting in pots is romance; survival in pots is solitude.
  • South-facing balcony? Use the morning light, shade-cloth in the afternoon. Forty degrees direct cooks roots through terracotta.

How to do it

Pick the right pot.

Terracotta, 25 cm minimum, with a saucer. Sit the saucer on small pebbles so the pot does not stand in water — drainage failure kills more herbs than drought.

Pick the right pot.

Mix the soil.

Half potting compost, half horticultural sand. Not builder's sand — that has lime. The mix should fall through your fingers, not clump.

Plant deep, water once.

Set the herb at the same depth it came in the nursery pot. Water generously, then leave for a week. Roots chase moisture downwards, which is what you want.

Finger-check daily, water by feel.

Two-centimetre finger test. Most days you will not water. The day you do, water until it runs out the bottom and stops. Half-watering is the worst of both worlds.

Frequently asked

Can I grow basil at all?
Yes, but accept it as a six-week plant. Basil exhausts itself by midsummer no matter what you do. Replace from the supermarket pots in mid-June if you cannot live without it.
Do I need feed?
Once at planting, then once a month with a weak organic feed. Mediterranean herbs are happier hungry; over-feeding makes leaves big and flavour weak.
What about winter?
Bay and rosemary survive a Lisbon winter outdoors with no protection. Oregano cuts back to woody stems and re-shoots in March. Move thyme and sage to a sheltered spot if there is frost in the forecast.
Why did my parsley die?
Three reasons, in order of likelihood: not enough water, too much sun, the soil drained too fast. Parsley is a temperate plant pretending to be Mediterranean. We do not pretend any more.

In closing

The balcony smells like rosemary by June and bay all year. We snip and cook, snip and cook, and the plants are bigger in October than they were in June. The trick was admitting that some herbs are not for forty-degree balconies and that a finger is the only watering schedule worth following. The graveyard cleared up nicely once we stopped putting basil in it.