At a glance
Rosemary is one of the most straightforward and most rewarding herbs to grow in a UK garden. Plant it in a sunny well-drained position, prune it once or twice a year, and it will produce fragrant, usable sprigs every month of the year for a decade or more. A mature rosemary plant in full flower in early spring is also a beautiful and valuable plant for early pollinators – the blue-purple flowers are among the first abundant nectar sources available to bees emerging in February and March.
The only way to reliably fail with rosemary in the UK is to plant it in poorly drained soil or a shaded position. Rosemary is a Mediterranean plant that evolved in hot, dry, rocky conditions – it hates wet roots and shade in equal measure. Get the drainage and the sun right and it is effectively an evergreen, year-round, low-maintenance herb that earns its place in the kitchen garden simply by being there.
Why rosemary thrives in the UK
The UK climate is not as reliably warm or dry as a Mediterranean summer but it suits rosemary reasonably well in most areas. The key factor is frost hardiness – most commonly grown rosemary varieties are fully hardy in the UK down to around -10°C, surviving all but the most severe UK winters without protection. In northern Scotland or exposed upland areas in winter, a sheltered south-facing position against a wall provides valuable extra warmth and protection.
Planting rosemary
Plant rosemary from March through to September, from pot-grown nursery plants. Spring planting gives the best establishment – the plant has the full growing season to develop a root system before its first winter. Plant in a position receiving at least six hours of direct sun per day. Rosemary planted in partial shade produces less aromatic growth and is more prone to legginess.
- 1Prepare the planting hole in free-draining soil – dig a hole twice the width of the pot. If your soil is heavy clay, improve drainage by mixing in grit or sharp sand at a ratio of roughly one part grit to three parts soil. Avoid adding compost – rosemary grows better in lean, poor soil than in rich, fertile ground.
- 2Plant at the same depth as in the pot – avoid burying the stem. Rosemary planted too deep is prone to stem rot. Plant at the same level as the nursery pot, firm gently around the roots and water in well.
- 3Space plants at least 60cm apart – mature rosemary plants spread to 60-90cm or more. Give them space from the start – overcrowded rosemary does not dry out properly between rains and is more prone to fungal problems.
Rosemary in containers is perfectly successful but needs very free-draining compost. Mix standard multipurpose compost 50:50 with horticultural grit or perlite for containers. Standard multipurpose compost alone retains too much moisture for rosemary in a pot. A terracotta pot is better than plastic as it allows moisture to evaporate through the walls.
Soil and drainage
Rosemary’s number one requirement is free-draining soil. Waterlogged roots in winter are the primary cause of rosemary death in UK gardens – a plant that survived several winters can be killed in a single wet winter if the drainage deteriorates or the plant becomes established in a low spot where water collects.
Do not add compost, manure or fertiliser to rosemary planting holes or as a mulch. Rosemary evolved in poor, alkaline, rocky soils – rich fertile conditions produce lush, sappy growth that has poor flavour and is more susceptible to frost damage. The leaner and drier the soil, the more aromatic and flavourful the rosemary.
Pruning for productivity
Annual pruning keeps rosemary productive, compact and long-lived. An unpruned rosemary becomes woody and bare at the base over time, producing most of its growth at the tips of increasingly long, sparse stems. Regular pruning prevents this and keeps the plant bushy and dense.
The main annual prune takes place after the spring flowering period, typically April to May. Cut back each stem by around one third, cutting into the current year’s soft growth. Do not cut back into old woody stems – rosemary does not regenerate from old wood. A second light trim in late summer removes any leggy growth and tidies the plant without interfering with winter hardiness. The critical rule: always cut back to where there is still visible green growth. If you cut into old wood the plant will not recover from that stem.
Harvesting and using
Harvest rosemary by snipping young, soft stem tips with sharp scissors or secateurs. The soft new growth at the tips is the most flavourful and tender. Avoid cutting into older woody stems during harvesting – save those cuts for the annual prune. Rosemary can be harvested year round in a UK garden, though growth is slowest in mid-winter. The plant produces the most aromatic and flavourful growth in summer after a warm, dry period.
Fresh rosemary stores well in the fridge wrapped in a damp cloth for one to two weeks, or can be dried by hanging in bundles in a warm, airy place. Dried rosemary loses some but not all of its flavour – it is a reasonable substitute in cooked dishes but no substitute for fresh when used as a garnish.
Common problems
A well-positioned rosemary plant in free-draining soil and full sun is one of the most reliable and rewarding herbs in the UK garden. Plant it once, prune it annually and it will provide an abundant, fragrant harvest for the kitchen year round for many years to come.
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