Looking like a pale, knobbly swede, celeriac won’t win any beauty contents, but it more than makes up for this by producing large, reliable crops during the colder months. It’s extremely hardy and can be left in the ground right through to spring – simply dig up plants whenever needed.
Although the edible part of celeriac resembles a rounded root, it is in fact a swollen stem, with a mild celery flavour. This versatile veg can be grated raw into winter salads or cooked and mashed like potato, added to stews and soups, or sliced and roasted. Rich in nutrients, antioxidants and fibre, celeriac is particularly good for the digestion, bones and heart.
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There are several varieties of celeriac available. Some are less prone to bolting (premature flowering) or resistant to disease, and newer varieties tend to be less knobbly, so are easier to prepare in the kitchen.
Look in particular for varieties with an RHS Award of Garden Merit (AGM), which shows they performed well in trials, so should grow and crop reliably – see our list of AGM fruit and veg for recommended varieties of celeriac and other crops.
You can also see many crops, such as celeriac and its close relative celery, in the fruit and veg plots at most RHS gardens, so do visit to see how they’re grown, compare different varieties and pick up inspiration and tips.
What and where to buy
Celeriac seeds are available in many garden centres and from online gardening retailers.
If you don’t have the time or space to sow celeriac indoors, or you only want a few, plug plants are available in spring, mainly from larger online retailers. However, plug plants are more expensive than buying seeds and the choice of varieties is very limited.
Celeriac needs at least six months to mature, but the seeds and young plants don’t like cold temperatures, so it should be sown indoors in early spring, to get it off to a good strong start. It can then be transplanted outside once temperatures warm up in late spring or early summer. Cold weather at this stage can cause celeriac to bolt, so take care not to plant it out too soon.
It’s not usually worth sowing celeriac outdoors in the UK – by the time temperatures are warm enough to sow, the crop wouldn’t have time to mature.
Growing celeriac from seed indoors
Place in a heated propagator at 15°C (59°F) or cover with a clear plastic bag and keep in a warm location.
Germination can be erratic and slow (up to three weeks). Once seedlings appear, move the pot or tray onto a bright windowsill or into a conservatory or greenhouse where the temperature stays above 10°C (50°F). Anything cooler can lead to premature flowering (bolting) later in life. Water seedlings regularly.
As soon as the seedlings are large enough to be handled, thin out those in trays to one per module and transfer those in pots into their own individual pot filled with multi-purpose compost and water them in well.
Start to harden off young celeriac plants towards the end of May, gradually acclimatising them to outdoor conditions.
You can then transplant them into the ground once all danger of frost has passed in your area – usually in late May or early June. Young celeriac plants are sensitive to cold at this stage, so delay moving them if temperatures are still low.
Space the young celeriac plants 30cm (1ft) apart, in rows 40–45cm (16–18in) apart. They like plenty of space and good air circulation. Take care not to bury the crown – the stem base should be at soil level. Water in well.
Protect the young plants from slugs and snails.
Covering them with cloches or fleece will improve growth and help to keep them warm, reducing the chances of bolting.
Regular and generous watering is the main priority. Also, as celeriac plants mature, gradually remove the outer leaves when they fall horizontal, to expose the crown and allow it to develop. Remove any side-shoots if they appear, along with damaged leaves, particularly any with dry patches or spots, which could be caused by celery leaf miner or celery leaf spot disease.
Celeriac is a moisture-loving plant, so keep the soil constantly damp – it should never be allowed to dry out.
Cover the ground with a thick layer of mulch, such as garden compost, to hold in moisture and deter weeds. Just be careful not to bury the plants’ crown.
Keep the ground weed-free, to reduce competition for light, water and nutrients. See our tips on controlling weeds.
Celeriac is hardy and can usually be left in the ground until required. It develops a stronger flavour over time. In colder sites, spread a thick layer straw around the plants to prevent the soil freezing, which can make harvesting tricky.
To prepare this rather strange-looking vegetable in the kitchen, remove the small roots and the often knobbly outer skin. (Smoother-skinned varieties are easier to clean and prepare.) Celeriac can grow quite large without turning woody. If you have more than you need, you can blanch and freeze any excess.
Celeriac is a versatile vegetable – it can be served raw, diced or grated into winter salads, or cooked in various dishes, including hearty stews. It can be steamed and mashed like potatoes, or sliced and roasted. It has a subtle, nutty, celery-like flavour.
If you haven’t harvested all your overwintered celeriac by spring, but need to free up space on the veg plot for new sowings, you can lift them and either transplant them into spare ground elsewhere or store in a cool shed or garage – just twist off the leaves, then place the celeriac in a container of potting compost or coir.
When growing in heavy soil or sites prone to winter waterlogging, it’s better to dig up and store celeriac in late autumn.
To produce a good-sized crop, celeriac needs plenty of water at all times, so make sure the soil never dries out. Plants may need watering several times a week in summer. Dig lots of garden compost into the ground before planting. Also mulch the soil around the plants with a thick layer of garden compost to hold in moisture.
Celeriac can be prone to bolting (flowering prematurely) if young plants are exposed to cold temperatures. So keep them indoors until late May or early June, harden them off carefully, then protect with cloches or fleece for a few more weeks. Choose bolt-resistant varieties too.
Young plants are also vulnerable to slugs and snails, so take steps to deter or control them.
Celeriac can be affected by celery leaf miner and celery leaf spot. To minimise problems, remove any leaves that have dry patches or spots, and avoid growing celeriac in soil where celery or celeriac have been grown in the past few years – see our guide to crop rotation.
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