RHS Growing Guides
How to grow celeriac
Our detailed growing guide will help you with each step in successfully growing Celeriac.
Getting Started
Looking like a pale, knobbly swede, celeriac won’t win any beauty contests, but it more than makes up for this by producing a tasty crop for the colder months. It’s extremely hardy and can be left in the ground right through to spring – simply dig up plants whenever needed.
With sufficient water and plenty of time, celeriac can provide substantial harvests
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. It is rich in nutrients, antioxidants and fibre.
Month by Month
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Choosing
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 and our Recommended Varieties below.
You can also see many crops, such as celeriac and its close relative celery, in the 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, then 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 limited.
Recommended Varieties
Earlier to reach cropping size than other varieties, has good resistance to disease and bolting.
Heirloom variety, introduced in 1871. Relatively smooth skin and slightly flattened base. Stores well.
A fast-growing, smooth-skinned variety that is quite vigorous, has good disease tolerance and stores well.
Preparing the Ground
Select a sunny or lightly shaded site ready for planting out in late May or early June. Avoid sites that dry out quickly – consistently damp soil is best, but it mustn’t become waterlogged.
Celeriac grows well in rich, moisture-retentive soil, so incorporate plenty of garden compost or other organic matter. If you’re practising no-dig, mulch the soil surface and plant directly into the mulch.
Sowing
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. It’s not usually worth sowing celeriac outdoors in the UK – by the time temperatures are warm enough for the seeds to germinate, the crop wouldn’t have time to mature.
Keep celeriac seedlings indoors, above 10°C (50°F), until at least late May
Sowing indoors
Start seeds off in March, sowing thinly in small pots or modular trays filled with peat-free seed compost. Cover the seeds with just a light sprinkling of compost. 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, taking up to three weeks. Once seedlings appear, move them 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 peat-free multi-purpose compost and water them in well. They can be planted outside once the weather is warm enough, usually from late May – see Planting, below.
Planting
Space celeriac plants 30cm (12in) apart, in soil that doesn’t dry out readily
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 and cover with cloches or biodegradable fleece to improve growth and help keep plants warm, reducing the chances of bolting.
Plant Care
As celeriac plants mature, gradually remove the outer leaves when they fall to 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.
Watering
Celeriac is a moisture-loving plant, so should be grown in soil that is consistently damp, otherwise this slow-growing crop would need a lot of watering over a long period. If the soil does dry out temporarily, then provide a good soaking, rather than watering little and often. See our watering guides below for more tips.
Mulching
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 crown of the plant.
Weeding
Keep the ground weed-free, to reduce competition for light, water and nutrients. See our tips on controlling weeds.
Harvesting
Celeriac may not be a thing of beauty, but it provides tasty harvests all winter
To prepare this rather strange-looking vegetable in the kitchen, remove the small roots and the often knobbly outer skin. Celeriac can grow quite large without turning woody. If you have more than you need, you can blanch and freeze any excess.
Storing
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, then either transplant them into spare ground elsewhere or store them in a cool shed or garage. To store, just twist off the leaves, then place the celeriac in a container of peat-free potting compost or coir. If you have heavy soil or the site is prone to winter waterlogging, dig up and store celeriac in late autumn.
Problems
To grow well, celeriac needs consistently moist (but not waterlogged) soil at all times. Celeriac can be prone to bolting (flowering prematurely) if young plants are exposed to cold temperatures. Slugs and snails might eat the leaves of young plants, and slugs tunnelling into celeriacs is sometimes a problem. Celery leaf miner and celery leaf spot can also affect celeriac. For more on how to tackle these issues, see Common Problems, below.
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