I Learnt How To Grow Celery In The UK As a Commercial Market Gardener & Grew it Outdoors & In Greenhouses and Tunnels. Here Are My Secrets To Great Crops.
If I had to give you one celery growing tip and one only it would be this. Celery, (Apium graveolens), is a marsh plant, you need to grow it as a marsh plant.
In other words celery originated in the fens and marshlands of various parts of the globe. We don’t know exactly when it was first cultivated but Pliny the Elder mentions it and it was found in Tutankhamun’s tomb (died 1323 BC). It later came into garden use in parts of Europe but was only used in England from the 1600s. John Evelyn recommends it in 1699. From then onwards it slowly displaced Alexanders as a garden vegetable in coastal regions.
In its wild form celery grows 1-3 metres high and is a biennial. Though I have had regrowth over three years when kept trimmed hard by constant harvesting. In its cultivated form is is much shorter growing. Celery is very fast growing in the right conditions.
Preparing The Soil For Celery
Being a marshland plant celery needs a very moisture retentive soil, which was a potential problem to me as my soil type was greensand! Outdoors I used to incorporate huge volumes of farmyard manure to my soil before planting celery. And I watered it for an hour or more everyday, EVEN when it rained.
In greenhouses and tunnels I always grew celery after adding large volumes of spent mushroom compost which I used to buy by the bulk lorry load. Again, I irrigated the crop every single day. Celery needs huge volumes of water even when the soil is moisture retentive.
How To Sow Celery
There are approx 17,000 celery seeds to the gram. They are like dust. One sneeze and you’ve lost a few grams of seed. This makes sowing potentially quite difficult as it’s hard to see individual seeds.
So how can it be sown?
The way I did it was to sow in seed trays for transplanting. Firm a moisture retentive compost in to a tray. Mix the celery seed with a carrier such as perlite or dry sand and sprinkle evenly across the moist compost. DON’T cover the seed with compost. Put a sheet of glass over the seed tray to retain moisture. The seed needs light to germinate. Germinate in a light warm place. I used an electric propagator set to 68F. After a few days the seed started to chit and grew like cress.
Once the seedlings have fully developed cotyledons (seed leaves) with the hint of the first true leaf appearing, was the time to transplant into modules. We used compost blocks which we made with a blocking machine. It produces a slab of what looks like a chocolate bar made of compost. The compost blocks/modules were 4cm square, so not huge.
We then carefully removed the seedlings from the seed tray. At this stage they have surprisingly long roots. We then laid the roots over the module and pushed them into the compost with a piece of split bamboo … you could use a long matchstick.
The prices looks rough and ready with some of the long root not fully buried. But if then kept at around 68F the seedling were standing upright the next day and growing away very fast.
A few weeks at this temperature and we had plants with 4-5 true leaves ready for planting.
I am normally against the use of perlite as it is energy expensive to produce and not very sustainable. But I will admit it is excellent for this purpose. In all my years I used it I used just a handful a year so consumed very little.
How To Plant Celery
Celery may start as a minute seed but it grows very rapidly. From weighing just one 17,000 of a gram to amateur plant that can weigh a kilo when trimmed. But few plants get this big as the consumer wants a smaller stick of celery.
The price of celery when sold commercially is per box. All the boxes are the same size but the number of sticks in box will vary depending on the size cut. Often the price of small sticks, cut early in the season, exceeds the value of that same stick if left to grow much bigger. So early in the season we chased the prices and filled the boxes with as many as 32 sticks. Later in the season, the bigger celery meant we could only get 12 sticks in the same box. Transport costs remained the same per box, so early crops made most money.
So we always chased early crops and prices.
This affects the planting system. A big stick of celery takes a lot of space whilst a small stick needs less space to grow in. So under glass or plastic we would plant at a distance of 12×12 inches and cut as soon as we could get a decent size stick. Later crops would be planted further apart. As far as 16X16 inches in my case.
And the earlier the crop was planted the better simply because they were ready to harvest much earlier. So under glass sand plastic we planted in March or April after lettuce crop. Outdoors we also planted in March.
March might sound very early in England. And indeed many years the weather would damage the crop. I’ve seen winds ripped all the leaves from the crop within days of planting. I’ve seen the crop disappear under late snows.
You might think this a disaster. But it wasn’t.
Not a Disaster
99% of the crop just shot up new leaves when the weather improved.
Celery is actually a hardy veg plant when young. BUT once it gets bigger it can succumb to frosts. It contains a lot of water and frost freezes the water and destroys the plant cells. But winter harvest are still possible as I explain below.
To get a succession of harvests we also grew later crops. These were sown and planted much later and were for summer or winter harvest.
Celery for winter harvest either need to be in a heated greenhouse OR, grown outdoors and covered.
Most autumns I would have a crop of 20,000 sticks for winter harvest. We’d cover the growing crops with a permeable sheet, then thick layer of straw, and finish with a plastic sheet that would shed the rain. It was a bit like a ridge tent. This would protect the crop down to around 10 degrees of frost.
When we wanted to harvest we just uncovered the crop and cut it. At Christmas it can be a lucrative crop.
Celery Transplant Shock
Some sources talk about seed not being sown until March out April or the plants could suffer transplant shock or bolt due to cold temperatures. In growing celery over several decades I’ve never experienced either of these problems .
Interestingly the biggest grower of celery in the UK also repeats the problems of transplant shock and bolting. So why did my neighbours and I not experience the same problem?
It’s hard to say. It could be soil type or similar.
How To Grow Celery
Celery needs to be grown in very moist conditions AND it needs plenty of nutrition. It’s one of the crops I fed at every watering. It craves nitrogen if it’s going to grow as fast as the plant can. But of course nitrogen is water soluble and will potentially get washed away with the irrigation.
So I would irrigate heavily with plain water and then give a weak feed in the last ten minutes. We didn’t want nitrogen leaching into the soil as we pulled all our water from a well below our market garden. It made me VERY conscious about leaching and water quality.
How to Harvest Celery
On a garden scale it is easy to grow celery and just harvest a few stalks (petioles) when needed. But commercially it is cut at ground level with a very sharp knife, any dead or diseased stalks removed and then trimmed for length. I made an open-ended box in which to place a dozen sticks of celery and then cut them with a big blade so they were all the same length.
Top Tip. The tastiest part of the celery in my view is the stem between where it joins the root. It is a sweet nutty flavour and very different to the rest of the plant. But its is usually thrown away!
Celery Varieties For The UK
Victorian gardeners blanched the stems of the celery plants by wrapping them in cardboard or similar materials to exclude the light. Sometimes they earthed the crop up like we do potatoes. This gave a white stem in the same way that some other veg are blanched whilst growing. Eg cardoons.
Earthing up made the crop dirty and I’m not in favour of it.
Then came varieties that were self blanching. Plus if the crop is densely planted the light is excluded anyway. The variety I grew, and still grow, is Lathom’s Self Blanching.
There are also green stemmed varieties where the amino is to ensure the stem remains a light green in colour.
Red or pink varieties are grown in some countries.
Fenland celery is a heritage celery variety and is grown mainly in the Fens of Cambridgeshire. The largest grower grows up to 15 hectares a year using very traditional methods tha involve a lot of labour. They don’t plant this variety until June and harvest tin October.
Types of “Celery”
So far I’ve written about stick celery. But there are related species. Leaf celery and celeriac. Leaf celery has thinner stalks. Celeriac is a bulbous root plant with a flavour reminiscent of the stem/root section I mentioned above. There’s also the wild celery that I mentioned at the beginning as being several metres high.
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