Sow
- MarchIndoors
Sow — Start seed in small pots or modular trays at about 15°C (59°F)
Celeriac
This Allotment Pro editorial draft summarises the cited RHS guide. Check the source and adjust timings for local conditions.RHS source guide
Month by month
Plant out
- Late May–early JuneOutdoors
Transplant — Harden off and plant only after frost danger has passed and temperatures are reliably mild
Harvest
- October–MarchOutdoors
Lift — Ease swollen stems from the ground as required through autumn and winter
1 - Getting Started
Celeriac is a slow-growing member of the celery family, cultivated for its rounded, knobbly swollen stem. Although it resembles a pale root or swede, the edible portion develops at soil level and has mild celery flavour. It can be grated raw into winter salads, mashed, roasted or added to soups and stews.
The crop is extremely hardy and may remain in the ground into spring, but it needs at least six months to mature. Starting indoors in early spring gives plants enough time to build a substantial stem before winter. Once established, celeriac needs relatively little intervention, provided its most important requirement—consistently damp soil—is met.
Is celeriac suitable for your plot?
Celeriac occupies ground through summer and autumn. It performs best where soil naturally holds moisture or where stored rainwater is readily available. Very free-draining ground that dries repeatedly can make this long season difficult and water-intensive. Choose sun or light shade and avoid waterlogged sites as well as drought-prone ones.
2 - Choosing What To Grow
Several celeriac varieties are available as seed, while plug plants offer a convenient but more expensive alternative in spring. Modern cultivars are often selected for smoother skin, easier kitchen preparation, resistance to bolting or disease, and reliable storage. RHS Award of Garden Merit cultivars have performed well in trials.
Recommended varieties
‘Asterix’ AGM
Earlier to reach cropping size than many varieties, with good resistance to disease and premature flowering.
‘Brilliant’
A smooth-skinned variety with white flesh that resists discolouration and stores well.
‘Giant Prague’
An heirloom introduced in 1871, with relatively smooth skin, a slightly flattened base and good storage qualities.
‘Ibis’ AGM
A vigorous, fast-growing, smooth-skinned cultivar with good disease tolerance and storage performance.
‘Monarch’ AGM
Smooth skinned, with succulent flesh, subtle nutty flavour and harvests beginning in September; it stores well.
‘Prinz’ AGM
A large cultivar with smooth skin, crisp white flesh and good flavour, resistant to leaf disease and bolting. ## 3 - Preparing The Ground Select a sunny or lightly shaded site where the soil stays consistently damp without waterlogging. Prepare it for planting in late May or early June. Avoid beds that bake hard or dry rapidly because interrupted growth limits the swollen stem.
3 - Preparing The Ground
Select a sunny or lightly shaded site where the soil stays consistently damp without waterlogging. Prepare it for planting in late May or early June. Avoid beds that bake hard or dry rapidly because interrupted growth limits the swollen stem.
Improving moisture retention
Celeriac appreciates rich, moisture-retentive soil. Incorporate plenty of well-rotted garden compost or other organic matter before planting. In a no-dig system, spread a generous surface mulch and plant directly through it. Organic matter both feeds this long-season crop and helps buffer moisture levels.
Clear perennial weeds before planting and leave enough open ground for 30cm (1ft) spacing. Good air circulation between plants helps foliage dry after rain, while fertile soil beneath them should remain evenly moist.
4 - Sowing
Sow celeriac indoors in March. Outdoor sowing is generally unsuitable in the UK because the soil becomes warm enough too late for plants to complete their six-month growing season. Seeds and seedlings also dislike cold, which may trigger bolting later.
Sowing indoors
Sow thinly in small pots or modular trays filled with peat-free seed compost. Cover with only a light sprinkling of compost, then place in a heated propagator at about 15°C (59°F). Alternatively, cover the container with a clear bag and keep it somewhere warm.
Germination can be slow and uneven, taking up to three weeks. Move emerging seedlings to a bright windowsill, conservatory or greenhouse that remains above 10°C (50°F). Water regularly and do not expose young plants to chilling.
Once seedlings are large enough to handle, thin modules to one plant each. Prick seedlings from shared pots into individual containers of peat-free multi-purpose compost and water them well. Keep them protected indoors until outdoor conditions are reliably warm.
5 - Planting
Plant home-raised seedlings or bought plugs outside after frost danger has passed, usually in late May or early June. Harden them off gradually. If nights remain cold, delay planting because young celeriac is particularly sensitive to low temperatures.
Spacing and depth
Set plants 30cm (1ft) apart in rows 40–45cm (16–18in) apart. This provides room for the broad foliage, swollen stem and air circulation. Keep the crown and stem base level with the soil surface; burying it can interfere with stem development.
Water thoroughly after planting. Cloches or biodegradable fleece help plants establish in warmth and reduce the risk of bolting, but remove or ventilate protection as conditions improve. Check that coverings do not restrict foliage or trap excessive heat.
6 - Plant Care
The central task is maintaining consistently damp soil through the long growing season. If the ground dries temporarily, give it a thorough soaking rather than repeated shallow sprinkles. This encourages deeper rooting and restores moisture through the main root zone.
Mulching and weeding
Apply a thick layer of garden compost or similar mulch to retain water and suppress weeds, but keep material away from the crown. Weed regularly so competing plants do not take light, water or nutrients from the crop.
Encouraging the swollen stem
As plants mature, outer leaves naturally fall towards the horizontal. Remove these gradually to expose the crown and let the swollen stem develop. Take off side-shoots if they appear, along with damaged or spotted leaves. Do not strip healthy upright growth that the plant needs for photosynthesis.
Watch foliage for dry patches, mines or spots that may indicate celery leaf miner or celery leaf spot. Prompt removal of badly damaged leaves and good spacing help keep the crown clean and ventilated.
7 - Harvesting And Storing
Lift celeriac from October through to the following March. The plants are hardy and may usually remain in the soil until needed, developing a stronger flavour over time. Ease each plant out carefully with a fork so the swollen stem is not cut or bruised.
Winter protection and kitchen preparation
In colder districts, surround plants with a thick layer of straw so the soil does not freeze solid and prevent harvesting. Remove the small roots and knobbly outer skin before cooking. Large stems generally remain usable rather than becoming woody, and excess prepared celeriac can be blanched and frozen.
Storing lifted celeriac
If the bed is needed for spring sowing, lift remaining plants and transplant them into spare ground or store them in a cool shed or garage. Twist off the leaves and set the stems in a container of peat-free potting compost or coir. On heavy or winter-waterlogged soil, lift the crop in late autumn rather than risking rot outdoors.
8 - Problem Solving
Most disappointing crops trace back to moisture stress or cold exposure. Keep soil damp but not saturated, maintain mulch, and protect young plants from low temperatures. Slugs and snails can damage foliage and tunnel into swollen stems; celery leaf miner and leaf spot may mark or weaken leaves.
Common problems
Bolting in vegetables
Premature flowering leaves celeriac unusable and is often triggered when seedlings or young plants encounter cold. Maintain temperatures above 10°C (50°F) indoors and wait for reliably mild conditions before planting outside.
Problem sourceCelery leaf mining fly
Larvae tunnel inside leaves, creating pale or scorched patches that eventually dry. Inspect foliage regularly and remove badly mined leaves before larvae complete their development.
Problem sourceSlugs and snails
These molluscs feed on young foliage and may tunnel into the developing stem. Reduce hiding places, protect vulnerable plants and check beneath foliage and mulch in damp weather. Source: Royal Horticultural Society. Structured as an Allotment Pro editorial draft for review; source facts and links remain attributable to the publisher.
Problem source