Plan a herb bed or planter: how many of each herb fits your space, compost needed, plus which herbs to grow together or apart, and how to water and prune them.
Choose your herbs
✱ Best grown in its own pot (spreads or discourages neighbours).
How to use this: Enter your bed or planter size, tick the herbs you want, and the calculator splits the space between them, estimates how many plants fit and the compost you’ll need — then flags any that should be kept apart.
Each herb is given a sensible plant-to-plant spacing (how far apart to set young plants). The tool shares your bed area equally between the herbs you pick, then works out how many of each will fit at that spacing. It also multiplies the area by the soil depth to estimate the compost (potting mix) you need to fill the bed or container.
The single most useful rule for a mixed herb planter is to group herbs by how much water and sun they want:
| Group | Herbs | Conditions |
|---|---|---|
| Mediterranean (drought-tolerant) | Rosemary, thyme, sage, oregano, tarragon | Full sun, free-draining/gritty soil, water sparingly |
| Leafy & thirsty | Basil, parsley, coriander (cilantro), chives, dill | Sun to part shade, richer soil kept evenly moist |
Herbs in the same group thrive side by side. Mixing the two groups in one container is the usual reason a herb planter fails — you can’t keep basil moist and rosemary dry in the same pot.
Always grow separately: Mint (spreads by runners and takes over) and fennel (discourages many neighbours) belong in their own pots.
A raised bed 1.2 m × 0.6 m (about 4 ft × 2 ft), 20 cm (8 in) deep, planted with basil, chives, thyme and rosemary:
Because this mix includes both thirsty (basil, chives) and drought-tolerant (thyme, rosemary) herbs, the calculator will remind you to zone them or use separate pots.
Switch between metric (metres, centimetres, litres) and imperial (feet, inches) at the top. Spacing is shown in your chosen units, and the compost estimate is given in litres, the way it’s usually sold.
Group herbs by their water and sun needs. Drought-tolerant Mediterranean herbs — rosemary, thyme, sage, oregano and tarragon — do well together in full sun and free-draining soil. Leafy, thirsty herbs like basil, parsley, coriander (cilantro), chives and dill prefer richer, evenly moist soil, so keep them as a separate group.
Keep mint and fennel on their own. Mint spreads by runners and quickly swamps its neighbours, so grow it in a pot. Fennel can inhibit the growth of many nearby plants. Also avoid mixing thirsty herbs with drought-tolerant ones in the same container, as you cannot water both correctly.
It depends on the herb. Small herbs like chives and coriander need about 15 cm (6 in), basil and oregano around 25–30 cm (10–12 in), and shrubby herbs like rosemary and sage 45–60 cm (18–24 in). This calculator uses these spacings to work out how many fit your space.
Leafy herbs usually need watering every one to two days in summer to keep the soil evenly moist, more for pots in full sun. Mediterranean herbs prefer to dry out slightly — let the top 2–3 cm (about 1 in) of soil dry before watering again, as they dislike soggy roots.
Harvest little and often. Pinch out the tips of basil and remove flower buds to keep it bushy, snip the outer stems of chives and parsley first, and lightly trim woody herbs through the season with a harder tidy after flowering. Never remove more than about a third of a plant at once.
