Celeriac has a similar flavour to celery, which is a close relative, but is hardier and more disease resistant. Although it looks like a large rounded root, the edible part is in fact a swollen stem. To grow well, it needs plenty of moisture, and should never be allowed to dry out. Newer varieties tend to be less knobbly, so are easier to prepare in the kitchen.
Jobs to do now
- Harden off seedlings before transplanting outdoors
- Plant out once all danger of frost has passed
Month by month
Start seeds off in March, sowing thinly in a small pot. Place the pot in a propagator at 15–18°C (59–65°F), or cover with a clear plastic bag and keep in a warm location. Alternatively, place in a coldframe in milder areas.
Germination can be erratic. Once seedlings appear, grow on in a frost-free greenhouse or coldframe, although good results are possible on a bright windowsill.
Transfer seedlings to individual small pots as soon as they can be handled. Keep at 15–18°C (60–65°F), as cold temperatures can lead to premature flowering (bolting).
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 keep the area weed free.
As the plants mature, remove the outer leaves when they fall horizontal, to expose the crown and allow it to develop. Remove any side-shoots if they appear.
You can harvest celeriac from October through to the following March. They develop a stronger flavour over time.
To harvest, carefully ease individual plants out of the ground with a fork.
Celeriac is hardy and can be left in the ground until required. It’s best to cover plants with a thick layer of bracken or straw during the cold winter months to prevent the soil freezing and make harvesting easier.
Alternatively, if you want to free up space on the veg plot for spring sowings, you can lift plants in early spring and either transplant into spare ground elsewhere or store them in potting compost indoors with the leaves twisted off.
Celery leaf spot: Brown spots appear first on older leaves, spreading to younger leaves.
Remedy: Use treated seed and rotate crops.
Slugs and snails
These feed on the young seedlings and you'll see the tell tale slime trail on the soil around your crop, as well as on the leaves.
There are many ways to control slugs and snails, including beer traps, sawdust or eggshell barriers, copper tape and biocontrols.
Celery leaf miner
Small larvae tunnel through the leaves, leaving brown blisters. Severe attacks check growth.
Grow under horticultural fleece or mesh. Pinch out affected leaves; do not plant seedlings with affected leaves. Parsnips can also be affected.
The Royal Horticultural Society is the UK’s leading gardening charity. We aim to enrich everyone’s life through plants, and make the UK a greener and more beautiful place.