Celery growing guide: from seed to harvest.

1. Know what celery likes Celery needs:

• rich soil
• constant moisture
• steady growth
• plenty of feeding
• cool to mild conditions

The big secret with celery is this: never let it get checked in growth. If it dries out, gets cold, or struggles, it can turn stringy, tough, or bolt.

2. When to sow In the UK, sow celery seed:

• indoors: February to April
• under cover in a greenhouse/polytunnel: March to April

Celery has a long growing season, so it’s usually started early indoors.

3. How to sow the seed Celery seed is tiny and can be slow to germinate. Sowing method

• Fill trays or modules with fine seed compost
• Firm lightly and water
• Scatter seed thinly on the surface
• Do not bury deeply — celery seed needs light to germinate
• Just press it gently onto the compost, or cover with the faintest dusting of vermiculite
• Cover with a clear lid or propagator top to keep humidity in

Temperature for germination

• Best at around 18–21°C
• Germination can take 10–21 days, sometimes longer

Keep compost moist, not soaked.

4. After germination Once seedlings appear:

• move them into bright light immediately
• keep them cool but frost-free
• avoid leggy growth

If sown in trays, prick them out once they are big enough to handle:

• transplant into modules or small pots
• hold seedlings by the leaves, not the stems

5. Potting on As plants grow:

• move them into larger modules or pots if needed
• keep them growing steadily
• never let them become pot-bound
• water regularly

A weak liquid feed every week or so helps once they are established.

6. Hardening off Before planting outside:

• harden off gradually over 7–10 days
• put them outside in the day and bring them in at night at first

Do not plant out too early. Cold weather can trigger bolting.

7. Planting out Plant out when:

• risk of hard frost has passed
• plants are sturdy and well rooted
• nights are no longer very cold

In many UK areas this is usually:

• late May to June

Spacing

• Space plants about 9–12 inches (23–30 cm) apart
• Leave 12 inches (30 cm) between rows

For self-blanching celery, slightly closer spacing is often fine.

8. Best growing position Celery likes:

• full sun or light shade
• sheltered conditions
• moisture-retentive, fertile soil

Before planting, enrich the ground with:

• compost
• well-rotted manure
• organic matter

Celery is a hungry crop, so rich soil makes a big difference.

9. Watering This is the most important part. Celery needs:

• constant moisture
• never to dry out

Water deeply and regularly, especially in dry spells. Mulching helps hold moisture in. If celery dries out:

• stems become stringy
• growth stalls
• plants may bolt

10. Feeding Feed regularly through the season. A good approach:

• add compost or manure before planting
• then use a nitrogen-rich liquid feed every couple of weeks during active growth

Celery loves rich feeding.

11. General care Keep plants:

• weed free
• well watered
• well fed

Remove any yellowing outer leaves as needed. Watch for:

• slugs on young plants
• aphids
• heart rot or poor growth from lack of water
• bolting after cold stress

12. Blanching celery Some celery varieties need blanching to make stems paler and milder. To blanch: Around 2–3 weeks before harvest:

• draw stems together gently
• wrap with cardboard, paper, or similar material
• leave the tops exposed

Do not trap lots of wet material around the stems, or they may rot. Many modern varieties are self-blanching, which makes life easier.

13. Harvesting Celery is usually ready:

• from August through October, sometimes later

You can:

• cut individual outer stems as needed
• or lift the whole plant when mature

Use a knife at the base, or lift with a fork.

14. How long it takes From sowing to harvest, celery usually takes about:

• 4 to 5 months
• sometimes a little longer

It’s not quick, but it’s worth it.