How to grow celeriac

Inspired by a helpful YouTube guide. We based this walk-through on Charles Dowding's detailed video "Celeriac how to grow and make bulbs | Sowing dates | Soil and spacing || Charles Dowding", which covers sowing dates, spacing, and the no-dig approach that keeps roots developing well. Charles grows in Somerset, so his timing suits the south of England closely. Worth a watch before you sow.

1. Sow indoors in late February or early March

Celeriac needs a long growing season - plant out in May, harvest in October. That is roughly six months in the ground, which means starting under cover while the weather is still cold.

The seed is tiny. Sow it on the surface of moist compost in a small pot or module tray. Do not cover it with compost. Celeriac seed needs light to germinate, so press it down gently and leave it exposed. A windowsill above a radiator is fine. Germination is slow - allow two weeks.

2. Prick out once the true leaves appear

The first leaves are seed leaves - small, oval, not quite what the plant will look like later. Wait for the true leaves, which are more jagged and celery-like. That is your cue to move each seedling into its own 7cm pot.

Handle the seedlings by the leaves, not the stem. They are fragile at this stage and a bruised stem usually means a dead plant. Use a pencil or a dibber to ease roots free. Keep them in a light spot and water regularly.

3. Pot on as the plants grow

If plants look root-bound before planting-out time, move them into 9cm or 10cm pots. Celeriac does not like to sit in a tiny cell for too long. That said, do not go too large too early - you want the roots to fill the pot.

Keep the plants well watered but not waterlogged. A liquid feed every couple of weeks from April onwards helps build strong plants before they go out.

4. Harden off over two weeks

Celeriac raised on a windowsill or in a warm greenhouse is soft and not yet ready for a Kent spring. Hardening off means gradually introducing the plants to outdoor conditions - cooler air, wind, lower night temperatures.

Start by putting trays outside in a sheltered spot for a couple of hours each day. Increase the time over a fortnight. If a cold snap is coming, bring them back in. Do not rush this step. Plants that skip it tend to check badly once they hit the ground.

5. Prepare the bed with plenty of compost

Celeriac wants rich, moisture-retentive soil. The ideal is ground that has had compost worked in, with no large air pockets for roots to fall into. Remove stones where you spot them.

If your soil is sandy and free-draining, add extra compost. If it is heavy clay, that is actually not bad for celeriac - it holds moisture, which is what the crop needs. A thick mulch of compost over the surface suits the no-dig method well and keeps moisture in.

6. Plant out after the last frost - usually late May in Kent

Mid-May is the safe bet for Sandwich and East Kent. If a late frost is forecast, wait. Celeriac plants are not delicate but cold snaps in May can set them back by a couple of weeks.

Space plants 30–35cm apart each way. Plant them at the same depth they were in the pot - do not bury the crown. Firm in gently and water well. The roots do not like to shift once planted, so get the spacing right first time.

7. Water consistently throughout the season

This is the single most important thing once plants are in. Irregular watering - dry spells followed by heavy rain or sudden irrigation - leads to poor bulb development, cracking, and hollow centres.

In a dry summer, aim for a thorough soak once or twice a week rather than a quick splash daily. The goal is to keep the soil evenly moist down to root depth. A mulch of compost or grass clippings around the plants helps retain moisture and suppresses weeds.

8. Remove lower leaves as the bulb swells

As the season goes on, the swollen base of the stem - the bit you eat - pushes up above the soil surface. Removing the lower, older leaves a few at a time encourages the bulb to develop and allows air to circulate.

Do not strip the plant bare - it still needs plenty of leaf to keep growing. Just take the ragged, yellowing outer leaves as they appear. Tidy is fine. Stripped is not.

9. Harvest from October, leave in the ground until needed

Celeriac is hardy enough to leave in the ground through a mild UK winter. In Kent the weather is generally kind, and roots left in the soil stay fresh longer than any stored inside. Lift as and when you need them.

If a severe frost is forecast, cover with a thick layer of straw or horticultural fleece. Roots can handle a degree or two of frost but prolonged hard freezes will damage them. On balance, it is better to lift the lot in late November if a serious cold spell looks likely.

When to call a handyman

Growing celeriac is a gardening job, not a handyman one. But if your veg plot needs raised beds building, a greenhouse base laying, or a new compost bin constructing, that is the kind of work Richard can help with in and around Sandwich.