Why a Sturdy Wooden Box Beats a Row of Pots

If your garden is a courtyard, a narrow side return or a balcony, you have probably already discovered the problem with individual pots: they dry out unevenly, they blow over in a gust, and they start to look scruffy the moment you forget to water them. A single deep wooden planter solves all three at once. The volume of compost holds moisture far more steadily, the weight keeps it upright, and the timber itself becomes a piece of furniture you can sit a mug of tea on.

Herbs also grow better in company. Grouped planting shades the compost surface, so the roots stay cool through a hot afternoon. For roughly the price of four decent terracotta pots, you can build something that will last a decade and earn its keep every summer.

Choose the Spot Before You Choose the Herbs

Almost every culinary herb wants sun, and most want at least six hours of it. Before you measure any timber, stand in the garden at midday and again at four in the afternoon and work out where the light actually falls. A south-facing wall or fence is ideal, and the warmth it radiates back at night will keep thyme and rosemary content well into autumn.

A few practical points worth checking first:

• Access to water. A planter this size needs a full watering can or two in dry spells. Site it within a hose length of an outdoor tap, or resign yourself to a lot of walking.
• Drainage. Never place it flat against a wall base where rainwater pools, and avoid the lowest corner of a sloping patio.
• Frost pockets. Cold air collects at the bottom of a slope or behind a solid boundary. Herbs in a raised box are more exposed than those in the ground.
• Reach. Keep the box near the kitchen door. A herb planter you have to walk past a shed to reach will go unpicked, and unpicked herbs turn woody.

Making the Box: Size, Timber and Drainage

A box measuring roughly 90 centimetres long, 30 centimetres wide and 25 centimetres deep is the sweet spot for a small garden. That depth matters: parsley throws a long taproot, and mint sends runners sideways rather than down, so it needs soil to travel through.

For the timber, choose untreated larch, oak or cedar if your budget allows, since these weather gracefully and pose no concerns around edible plants. If you use pressure-treated boards, line the inside with a heavy-duty membrane, pierced at the base, so the compost never touches the preservative directly. Boards around 20 millimetres thick give you enough rigidity without becoming immovable.

Fix the sides with brass or stainless-steel screws, which will not corrode in damp compost. Then turn the box over and drill 20-millimetre holes every 15 centimetres along the base, plus a couple in the lower edge of each long side as a belt-and-braces measure. Screw two battens underneath as feet so the base sits clear of the ground and water can escape freely. Without that airflow, a wooden planter becomes a slug hotel by mid-July.

Compost and Planting Up

Divide the box into three sections with thin internal battens, because the herbs you have named want quite different conditions. Use a peat-free multipurpose compost throughout, but amend each compartment individually.

• Mint is the thug of the herb world. Sink it in its own pot, rim above compost level, or give it a compartment to itself and be ruthless about pulling out runners that stray.
• Thyme wants lean, gritty, free-draining ground. Mix two parts compost with one part horticultural grit, and add a handful of grit as a mulch over the surface.
• Parsley is the opposite: rich, moisture-retentive compost with a little well-rotted garden compost worked in, kept consistently damp.

Set the plants so the top of each rootball sits level with the compost surface, firm them in gently with your knuckles, and water well. Leave 20 to 25 centimetres between parsley plants, as they bulk out quickly.

Watering, Feeding and Seasonal Care

Water at the base in the early morning, aiming for the compost rather than the foliage, and check the parsley and mint compartments first — they will dry out long before the thyme does. In a hot spell, that may mean daily watering; in a wet British week, not at all.

Feed the parsley and mint with a diluted liquid seaweed feed every fortnight from late spring to late summer. Leave the thyme alone; rich feeding makes it soft, floppy and flavourless.

Harvest little and often. Pinch parsley from the outer stems, cutting right down at the base rather than stripping the crown. Snip mint above a pair of leaves to keep it bushy. With thyme, take the soft tips only — cutting back into old, woody growth rarely regrows.

Come autumn, cut mint to the ground after it dies back, and sow a fresh batch of parsley in late summer for a spring crop, since parsley is biennial and loses vigour in its second year. Thyme overwinters happily if the box drains well, though in a wet, cold spell it pays to move the planter against a sheltered wall and ease off the watering entirely.

Small Adjustments That Make a Big Difference

If slugs are shredding the parsley, run a copper tape strip around the top edge of the box or set it on gravel feet. If you spot yellowing leaves on the thyme, that is almost always waterlogging rather than hunger — check the drainage holes are clear. And if your parsley bolts in a heatwave, keep picking the outer stems to delay flowering, and keep the compost damp.

One box, three herbs, and a sunny corner within reach of the door. That is a herb garden most small spaces can happily accommodate.