Celery has a reputation as the most difficult thing in the vegetable garden, and it is only half deserved. Nearly every failure comes down to one of two mistakes, and both are made early: the seed goes in too deep, so nothing ever appears, or the young plant is checked by cold and spends the summer building a flower stem instead of stalks. Get those two right and most of what is left is a watering can.
It helps to know what you are actually growing. Apium graveolens is a marsh plant. Wild celery — smallage — grows in brackish ditches and on salt marshes around the coast, in ground that is never dry and often barely drained. Almost everything the cultivated forms do makes sense once you hold that picture in mind. This guide covers sowing the light-hungry seed, avoiding the cold check that causes bolting, the difference between trench celery, self-blanching celery, cutting celery and celeriac, and how to lift and store the roots in November.
- Sow February–April under cover · celeriac by mid-March for a long enough season
- Germinate 14–21 days at 15–20 °C — surface-sown, because the seed needs light
- Space 25–30 cm apart · self-blanching types in blocks, 23 cm each way
- Harvest Celery from August · celeriac October–November, before the hard frosts
A marsh plant in a vegetable bed
Celery has shallow roots and broad, thin leaves. It loses water quickly and cannot go and find more. That one fact explains the stringy stalks, the bitter edge, the hollow hearts and the plants that run to flower in July — all of them are the signature of a plant that went short of water at some point, usually during a few days in June that nobody noticed at the time.
So the groundwork matters more here than for most crops. Dig a generous quantity of well-rotted compost or manure into the bed over winter; the old habit of growing celery in a trench existed for exactly this reason. Our guides to preparing your soil and composting cover the groundwork, and once the plants are in, the aim is roughly twenty litres per square metre a week in a dry spell, with a mulch to hold it there. Read watering your garden and mulching and weed control before you sow rather than after. Celery is also notably salt-tolerant, a legacy of those coastal ditches, which is why it shrugs off seaweed feeds and coastal gardens that defeat other vegetables.
Why celery seed so often fails to come up
Celery seed is minute — roughly 2,500 seeds to the gram — and, unusually for a vegetable, it needs light to germinate. Sow it on the surface of damp, fine compost, press it down with a flat board so that it makes proper contact, and leave it uncovered, or give it the thinnest possible dusting of vermiculite. Most packets that "never came up" were simply buried. Cover the tray with a clear lid or a sheet of glass to hold the moisture, keep it at 15–20 °C, and expect two to three weeks. Above about 25 °C the seed goes dormant rather than faster, so an airing cupboard is the wrong place for it.
If nothing appears, work through how to germinate seeds and why seeds are not germinating. Seed starting indoors covers the trays, lids and light levels you need in February, and leggy seedlings explains what to do when the first ones stretch. Celery seed stays usable for about five years in cool, dry storage — see how long seeds last and understanding seed packets.
The cold check that causes bolting
This is the part that catches people out. Celery and celeriac are biennials: the plan is a plant in year one and flowers in year two, and they decide which year it is by counting cold. A young plant held below about 10 °C for ten days or more reads that as a winter gone by, and goes straight to a flower stem in midsummer — tough, hollow and finished.
Two rules follow. Do not sow before February, however keen you are, because a seedling raised in an unheated greenhouse in January is precisely the plant that bolts. And do not plant out until the nights are reliably above 10 °C, which in most of Britain means the last week of May or the first week of June — later than almost anything else you will be hardening off. Take a full fortnight over it, as our guide to hardening off seedlings sets out, and if a cold snap is forecast after planting, throw fleece over the row; cloches, fleece and cold frames covers the options.
Sowing celery and celeriac, step by step
- Surface-sow in February or March Scatter thinly on damp seed compost, firm, do not cover. Celeriac needs the longest season of the three, so get it in by mid-March; celery can follow in late March or April. Everything tagged for February and March sowing is gathered on one page.
- Prick out at the first true leaves One seedling per module, held by a leaf and never by the stem — celery stems are brittle and a crushed one rots. Deep modules give the roots somewhere to go while you wait for June.
- Grow them on cool but not cold Around 15 °C is ideal. Warmer and they get soft and leggy; colder and you risk the vernalisation that leads to bolting. Keep them evenly watered — a celery seedling that wilts once never quite forgives you.
- Plant out from late May, 25–30 cm apart Self-blanching celery goes in a block rather than a row, 23 cm each way, so the plants shade one another. Celeriac is planted shallow, with the crown sitting on the surface: the swelling is a stem base, not a root, so it must never be earthed up. Container growers should use a pot of at least 25 cm — see container gardening from seed.
- Water hard and feed fortnightly Celery is one of the few crops where over-watering is almost impossible. A liquid feed every two weeks from midsummer keeps the stalks thick and the celeriac swelling — see feeding and fertilising.
Celery, celeriac — or cutting celery?
Celery (var. dulce)
Grown for thick, juicy leaf stalks in an upright head.
- Pascal, Golden Self Blanching and organic Tall Utah 52-70 in our range
- Trench types need blanching; self-blanching types are planted in blocks and left alone
- Cut from August to the first real frosts — it is not hardy and will not stand the winter
Celeriac (var. rapaceum)
The same species bred for a swollen stem base rather than stalks.
- Monarch and Dolvi, both smooth-skinned and slow to discolour
- Needs a full 30 weeks, so it is the one to sow first and never to rush
- Lifted in late autumn and stored in damp sand until March — much the better keeper
There is a third form that deserves more attention than it gets. Cutting celery, or leaf celery — var. secalinum, sold as Gewone Snij and Amsterdamse Donkergroene — makes no stalk and no root worth eating, but produces armfuls of intensely flavoured leaf that goes into stock, soup and stuffing. It is grown exactly like parsley, needs no blanching, tolerates light shade and stands outside all winter. If celery proper has defeated you twice, start here: it is the easiest plant in the whole Apium graveolens range and it lives happily among the herbs rather than in the vegetable bed.
Blanching, lifting and storing
Blanching excludes light from the stalks so that they stay pale, tender and mild. With trench varieties such as Pascal you wrap a collar of cardboard or thick newspaper around the bundled stalks about three weeks before you want to cut, leaving the leaves free, and top it up as the plant grows. Self-blanching kinds do most of the work themselves when planted in a block, though the outer row always stays greener — tuck straw around the edge of the block if you mind. Whatever you use, check under the collars for slugs, which regard them as accommodation; common garden pests covers the defences.
Celeriac wants the opposite treatment: pull off the lower and side leaves from August so the crown sits clear of the soil, and scrape the earth back from its shoulders to let the swelling expand. Lift from October, before the ground freezes hard — the roots take a touch of frost and are the better for it, but not a prolonged one. Trim the leaves and whiskery roots, and pack them in damp sand in a cool shed alongside your carrots and beetroot, as set out in storing root vegetables over winter.
One warning about neighbours. Celery is in the carrot family, so carrot root fly will attack celeriac just as readily as a carrot, and celery leaf miner blisters the foliage of both. Fine mesh over hoops solves the first; picking off blistered leaves solves the second. Do not follow carrots, parsley or parsnips with celery in the same ground — see crop rotation made simple. Leeks make a much better neighbour, and want the same rich, damp soil.
Common mistakes
- Covering the seed. Celery needs light to germinate. Surface-sow, firm, and resist the urge to rake soil over it.
- Sowing in January. An early start does not help. A seedling that gets cold enough for long enough will bolt in July whatever you do afterwards.
- Planting out in early May. Celery is one of the last things to go outside, not one of the first. Wait for nights above 10 °C.
- Letting it dry out once. A single check in June is what makes stalks stringy and bitter in August. There is no fixing it later.
- Earthing up celeriac. The swelling is a stem, not a root. Buried, it grows whiskery and small instead of round and smooth.
Frequently asked questions
Why is my celery stringy and bitter?
Almost always drought, and almost always weeks before you noticed. Celery that runs short of water builds tough fibre in the stalks and concentrates the bitter compounds in the leaf. Blanching softens the flavour of trench varieties considerably, and picking the inner stalks rather than the outer ones gives you the mildest part of the plant, but the real answer is more water, earlier, and a thick mulch.
Can I sow celery in autumn?
No — this is a February-to-April crop and nothing is gained by trying. Cutting celery is the only member of the family worth sowing late, and even that wants to be in by the end of August. If you are looking for something to fill the bed now, what to sow in September and the September sowing list have the alternatives; put celery on the calendar for February instead.
Do I have to blanch celery?
Only if you are growing a trench variety and want pale, mild stalks. Self-blanching types like Golden Self Blanching and Tall Utah are bred to do it themselves in a block planting, and cutting celery is never blanched at all. Green, unblanched celery is perfectly edible — just stronger and more assertive, which is exactly what you want in a stock.
Will frost spoil celeriac in the ground?
A light frost will not; celeriac takes several degrees below zero and the flavour sweetens a little. What ruins it is a long freeze that catches the exposed shoulders, or leaving it in heavy wet soil into the new year, where it rots. Lift through October and November, trim, and pack it in sand. Stored that way it will still be firm in March, long after the celery has gone.
Celery rewards patience more than skill. Sow it on the surface, keep it cool but never cold, plant it late, water it far more than feels reasonable, and it will give you something the supermarket cannot: stalks with flavour, and a celeriac that keeps until spring. Because it is a biennial, saving your own celery seed takes two summers and a plant left to flower; if you want to start seed-saving this month instead, a cucumber left to go yellow on the vine ripens its seed in the same season. Browse the celery, celeriac and organic celery ranges, the whole Apium graveolens species, everything else in vegetable seeds and organic vegetables, or work through the rest of our growing guides.
