Show-off celery

There are so many things that can and do go wrong when growing celery, but don’t let that put you off, a good specimen is a delight to behold! This difficulty is exactly why the NVS and the RHS award 20 points (the highest available) to trench or blanched celery and 18 points for self blanching celery.

Celery, in its natural habitat, is a bog plant, so should be grown in a rich, high organic matter content growing medium, which must never be allowed to dry out, especially in summer and early autumn when they are reaching maturity.

Seed sowing

Celery is grown from one of the smallest of vegetable seeds. As the seed is too small to space out individually, it is sown broadcast, as thinly as possible, on a tray of multi-purpose compost. The tray is given a good watering before sowing and I do not cover the seeds with compost. I just press them lightly into the compost.

The seeds need heat for germination, so they go into a propagator or on a soil warming bench. They take about two weeks to germinate, and when they are large enough, I transfer the seedlings into small pots (used cups from vending machines are ideal and cheap!).

Another alternative is to sow the seeds into multi-cell trays, a few seeds into each cell. When they germinate, they are reduced to one plant in each cell. The time of sowing depends on the date you require them for showing or eating. A sowing in early February will give you mature plants in August. If you need them for September, you do not need to sow until late February. If you want to spread the maturity dates, it may be advisable to make two sowings a month apart.

When the plants are too big for the small pots, they are potted on into four or five inch (100 to 125mm) pots. In April the plants are hardened off in a cold frame and then planted out eighteen inches (450mm) apart when all likelihood of a frost has passed.

The most important thing to remember when growing celery, is that in their wild state they are bog or streamside plants and therefore need a lot of water. Another thing is that they are one of the slug’s favourite meals. For suggestions with how to deal with them, see pests and diseases guidance below. As regards feeding, I usually give two or three feeds of a seaweed fertiliser in May and June, and a feed of phostrogen in July, because this has a higher potash content to harden the growth. 

One problem with celery is heart rot which can be devastating. I think it can be caused by too much feeding with nitrogen which softens growth, which is why I have suggested high potash feeding towards the end of its growth cycle. Also, what I have suggested about preventing the plants from sweating, should help to prevent this problem. Medwyn Williams recommends watering the plants with a 2% solution of Calcium Nitrate, trickling the solution onto the foliage and into the heart of the plant. The Calcium he says, hardens the tissues in the heart and thus helps to prevent heart rot. 

Harvesting

It is advisable to leave the celery as near to the show date or use date as possible before lifting because it can go limp if left out for very long. You will need to lift them with a fork pushed right under their flank. They have quite a large rot system which is normally cut with a knife into a wedge shape. The plants need to be washed thoroughly, paying particular attention to between the sticks. Remove completely any sticks which are damaged, hoping that there are not too many!.
 
   

Pests and diseases

Slug damage is probably the number one pest of celery, evidenced by bitten, brown edges at the base of the leaf stalks. Non-chemical measures include the use of nematodes (trade name "Nemaslug") or using sharp grit sprinkled around the base of each plant as slugs find it difficult to travel across grit. It doesn't kill them just stops them damaging your celery plants. Frogs and birds love slugs so if you have a pond nearby let the frogs do the work for you. Traditional methods include slug pellets as a first course of action. Chemical pest controls are no longer recommended, but as a last resort for  show celery, a liquid slug killer is effective when applied form above, helping to get rid of eggs and young slugs in the heart of the plant.

Celery leaf minor, this is becoming a serious pest, the maggots leave tunnels in the leaves, and a bad attack can almost remove all the sap in the leaves. In the past insecticides would have been used, however this is no longer recommended due to the impact on pollinators. Contact sprays have little effect as the leaf skins protect the maggot, so the best solution is to remove the leaves with maggots by hand.

Bolting or premature flowering is evidence of stress at some stage in the growth of the plant, particularly prevalent as a result of underwatering. Also avoid planting too early or in cold soil. Once the seed head is seen the plant has completed its life cycle and is not fit for eating.

Heart rot has been discussed earlier, and finally;

Celery leaf spot is becoming more prevalent, and currently I don’t think there is a control that we can buy as amateur growers that will control this disease.
 
 

Cultivars (or varieties most commonly grown)

 Self-blanching cultivars, although useful, are easier to grow, although seldom, if ever, grown for the show bench. Must be grown in a block so they blanch each other, I also use scaffolding boards round the outside of the block to blanch those grown at the edge of the block. Useful varieties include, Victoria, Lathom self-blanching, Loretta and Octavius. These also mature up to one month earlier than the trench types.

Those grown for exhibition are almost without exception trench cultivars. “Ideal” has been the standard cultivar for many years, but more recent ones are Evening Star, supplied by Medwyns of Anglesey, as seed and seedlings and a new variety introduced in 2018 is “Discovery”, seed supplied by Select Seeds of Derby. I grew this as a trial last year and it performed very well for me, but you must start the blanching process early. If a pink variety tickles your fancy, than “Giant Red” is the one to go for.

Points for celery:

About David Allison

David Allison is Horticultural Adviser at The National Allotment Society. 

With a farming background, David is vice chairman of the RHS fruit, vegetable and herb committee and accredited RHS floral judge. He is also Chairman of the Vegetable Trials Forum at the new RHS Gardens at Bridgewater and an accredited National Vegetable Society judge and lecturer - amongst other things!