A raised bed is one of the best homes for a herb garden. It lifts the plants to a comfortable working height, it warms up earlier in spring than ground-level soil, and — most importantly for herbs — it drains freely, which is exactly what Mediterranean herbs such as rosemary, thyme and lavender need. In heavy clay soil, where herbs in the open ground often rot over winter, a raised bed can be the difference between a herb garden that thrives and one that fails.
A herb raised bed also lets you give different herbs different soil in the same bed. One end can be gritty and lean for the Mediterranean herbs, and the other end richer and moister for basil, parsley and mint — though mint should still be kept in a pot sunk into the bed, because even in a raised bed it will spread. This guide covers building the bed, filling it, laying it out, and caring for it. If you are unsure about materials or soil for your area, check your local extension service for advice.
Building the raised bed
A herb bed does not need to be deep — 20 to 30 centimetres of soil above ground level is enough for most herbs, though 30 to 40 centimetres is better for deep-rooted perennials such as rosemary and for beds built on concrete or heavy clay. Make the bed no wider than about 120 centimetres, so you can reach the middle from either side without stepping on the soil, and as long as your space allows. A bed by the kitchen door, in the sunniest spot you have, will be used far more than a bed at the far end of the garden.
Use untreated timber, stone, or brick for the sides, and avoid treated timber or old railway sleepers that may leach chemicals into soil where you grow food. Line the sides, not the base, if you want to slow rotting, and leave the base open so worms can move in and excess water can drain away. If you are building on concrete, drill drainage holes or leave gaps at the base, and add a layer of coarse gravel before the soil. Our raised bed soil calculator can help you work out how much soil you need to fill the bed.
Filling the bed: two soils in one bed
The clever trick with a herb raised bed is to fill it with two different mixes. For the Mediterranean end — rosemary, thyme, sage, oregano and lavender — use a lean, gritty mix: roughly equal parts topsoil, compost and coarse grit or sharp sand. This drains fast, stays lean, and keeps the flavours concentrated. For the soft-herb end — basil, parsley, cilantro, chives and dill — use a richer mix with more compost and less grit, because these herbs want steadier moisture and more nutrients.
Fill the bed a few centimetres proud of the sides, because the soil will settle over the first weeks. Water it well and let it settle before planting, and top it up if it sinks. Do not fill a raised bed with pure compost — it shrinks, it holds too much water in winter, and it is too rich for Mediterranean herbs. A mix of topsoil and compost, with grit where drainage matters, is the right balance. For quantities, use the raised bed soil calculator and the soil volume calculator.
Laying out the herb bed
Put the tallest herbs at the back or in the centre, and the low, spreading herbs at the front where they can tumble over the edge. Rosemary and lavender grow into woody shrubs and belong at the back of the bed, where they will not shade the smaller herbs. Sage and oregano are mid-height and go in the middle. Thyme, chives and parsley are low and go at the front, where they are easy to pick. Leave room for growth: a rosemary plant that looks small in its first year can be a metre across in three years, and an oregano plant spreads steadily.
Keep mint in a pot sunk into the bed, with the rim a few centimetres above the soil, so its runners cannot escape — even in a raised bed, mint will take over if it is planted direct. Give dill and fennel their own corner, because they grow tall and fennel is best kept away from most other herbs. And leave a small gap for annuals: basil and cilantro are sown fresh each year, so keep a patch of the bed free for them in spring. Our plant spacing calculator can help you work out how many plants fit.
Watering and feeding a raised herb bed
Raised beds dry out faster than ground-level beds, especially in sun and wind, so check the soil regularly in summer. Water deeply, so the moisture reaches the roots, and water in the morning so the leaves dry quickly. Mediterranean herbs in the gritty end of the bed need less water than the soft herbs in the rich end — water the two ends differently, rather than watering the whole bed the same way. Mulch the soft-herb end with compost or straw to hold moisture, but do not mulch the Mediterranean end heavily — a light gravel mulch suits rosemary and thyme better, because it keeps the crown dry and reflects heat up into the plant. Our guide to mulch types explains the options, and the watering calculator can help with quantities.
Feeding is light. A dressing of compost over the soft-herb end in spring is enough for most herbs, and a liquid feed at half strength once a month is plenty for basil and parsley in summer. The Mediterranean end often needs nothing more than the compost it was planted in — over-feeding makes rosemary and thyme grow soft and flavourless. If a herb looks pale and hungry, check the soil with a test through your local extension service before feeding, so you feed what is actually missing.
Seasonal care for the raised herb bed
In spring, clear dead growth, top-dress the bed with compost, and sow or plant the annual herbs — basil, cilantro and dill — after the last frost. Prune rosemary and lavender lightly after flowering, and never cut into bare wood. In summer, harvest little and often, pinch basil to keep it bushy, and water the soft-herb end more than the Mediterranean end. In autumn, take a last harvest of tender herbs before the frost, cut back dead annuals, and leave the perennials standing — their foliage protects the crown over winter.
In winter, the raised bed drains well, which helps perennials survive wet weather, but the roots are more exposed to cold than in the open ground. In cold climates, protect the bed with fleece on the coldest nights, and do not let the soil dry out completely in cold, windy weather. Use winter to plan: note which herbs thrived and which struggled, and move any herb that is in the wrong soil to the other end of the bed in spring. A herb bed is a long-term planting, and a small adjustment each year keeps it productive for many years.
Common mistakes
The most common raised-bed mistake is filling the whole bed with one rich mix, which suits the soft herbs but rots the Mediterranean herbs over winter. The second is planting mint direct into the bed, where it spreads through the whole bed within a season. The third is building the bed too wide to reach the middle without stepping on the soil, which compacts it. The fourth is planting perennials such as rosemary too close together, so they crowd each other within two years. And the fifth is forgetting that raised beds dry out faster than ground-level beds — check the soil in summer, and water the soft-herb end before it wilts.
| Bed zone | Soil mix | Herbs | Water |
|---|---|---|---|
| Mediterranean end | Topsoil, compost and coarse grit, roughly equal parts | Rosemary, thyme, sage, oregano, lavender | Less; let soil dry between waterings |
| Soft-herb end | Topsoil with more compost, little grit | Basil, parsley, cilantro, chives, dill | More; steady moisture, mulch to hold it |
| Mint corner | Pot sunk into the bed | Mint only, in its own pot | Moist; pot prevents spreading |
Frequently asked questions
How deep should a raised bed for herbs be?
Twenty to thirty centimetres of soil is enough for most herbs, though thirty to forty centimetres is better for deep-rooted perennials such as rosemary and for beds built on concrete or heavy clay. Make the bed no wider than about 120 centimetres so you can reach the middle from either side.
What soil should I put in a raised herb bed?
Use two mixes: a lean, gritty mix of topsoil, compost and coarse grit for Mediterranean herbs such as rosemary, thyme and lavender, and a richer mix with more compost and less grit for soft herbs such as basil, parsley and cilantro. Do not fill the bed with pure compost.
Can I grow mint in a raised bed?
Only in a pot sunk into the bed, with the rim a few centimetres above the soil. Mint spreads by underground runners and will take over a raised bed within a season if it is planted direct into the soil.
How do I arrange herbs in a raised bed?
Put tall herbs such as rosemary and lavender at the back, mid-height herbs such as sage and oregano in the middle, and low herbs such as thyme, chives and parsley at the front. Leave room for growth — rosemary can be a metre across in three years.
Do raised herb beds need more watering?
Yes — raised beds dry out faster than ground-level beds, especially in sun and wind. Water deeply in the morning, water the soft-herb end more than the Mediterranean end, and mulch the soft-herb end to hold moisture.