How to grow celeriac

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.

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. 

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. 

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.

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. 

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.