Delicious crunchy celery (Apium graveolens var. dulce) is a delightful, useful cool season plant that is sometimes tricky to grow. This shouldn’t stop you from giving it a go because commercial non-organic celery has one of the highest pesticide spray residues of any vegetable. At the very least you can grow soup or Asian celery (A. graveolens), which is used mainly for its leaves and narrow stems. It is not crisp or sweet but has a great strong celery flavour, perfect for soups, stews and stir-fries. It is also easy to grow and needs less water.
Celery does not like extreme temperatures, either hot or cold, so in temperate regions sow seed in late winter – early spring and again late summer – autumn. Avoid frosts because a few days of temperatures below 10°C will cause seedlings to bolt to seed. In the sub-tropics seed is best sown from April – August. In the tropics, celery can only be grown in the dry season, so plant seed from April – July. Soak the tiny seed overnight in warm water, then mix with a little sand, sprinkle over the surface of the seed-raising mix and cover only very lightly with more mix. Seed germinates best at soil temperatures from 15 – 21°C but it usually takes 2-3 weeks for green shoots to appear. Water carefully and keep moist at all times. Seed can go into a seedling tray and later be pricked out into small pots, but I like to sow straight into small biodegradable pots that are planted into the garden once the seedlings have been thinned out and reach a reasonable size. Liquid feed with seaweed and fish emulsion at least twice during the 4-6 weeks before planting out. In cooler regions you can sow seed in the next few weeks, so you have seedlings ready to plant out once the last chance of frost is over. Some cultivars worth trying are ‘Golden Self-blanching’, ‘Green Pascal’, ‘Red-stalked’, ‘Stringless’, ‘Tall Utah’, ‘Tendercrisp’,
Celery will grow in most soils but does best in a rich, moist well-drained sandy loam that has been dug over 2-3 weeks before planting and compost, potash and well-rotted manure added. It does best in slightly acid to neutral soil (pH of 5.5 – 7), prefers sun or partial shade and needs some protection from wind.
Whether you buy seedlings, or grow your own, plant your celery once the last chance of frost is over. It is a great ‘fill-in’ crop in a crop rotation system because it doesn’t need to be moved every year. Space plants 20-25 cm apart in a block, this encourages the stems to grow longer, fleshier and slightly more pale, and helps to control weeds.
Celery, although a biennial, is grown as an annual and is harvested before plants begin to flower and stalks become more fibrous. Mulch well and keep well watered to avoid moisture stress. Watering in the morning at ground level will help to reduce fungal problems. While celery is growing rapidly it needs to be fed regularly, I give it some liquid manure, worm juice or weed tea every couple of weeks.
Blanching and harvesting
Blanching (excluding light from the stems) produces sweeter, more pale stalks. If you only use leaves and stalks for cooking then I wouldn’t bother, but if you love to eat it fresh, then certainly try blanching. Some varieties are known as self-blanching and although these do tend to be paler and crisper, they can still be improved by excluding light as well. The traditional method of blanching was to plant seedlings into trenches and gradually hill the soil around the plants as they grow. I find it much easier to wait until the plants are a decent height, then gather the stalks in a bunch and tie loosely. Wrap the stems of each plant in thick paper, cardboard or a milk carton with the bottom cut out, leave the leaves sticking out the top. You can also hill some of the surrounding soil around the plant to exclude more light. Continue to water regularly. After 2-3 weeks, the stalks should be pale and ready to harvest. When picking celery you can either carefully lift the whole plant using a fork, or just harvest single outside stalks as you need them.
Pests and diseases
Celery is relatively pest and disease free. Keep snails and slugs under control, especially if blanching. In humid conditions there may be some fungal problems, but if you remove affected leaves, or whole plants, then this will stop it spreading.
The delicious crunch and flavour of celery makes it perfect for salads and stir-fries and it is an essential ingredient of stocks and soup. Celery is also an important medicinal plant with the seeds, stalks and juice being rich in potassium, calcium, vitamin C, folate and mineral salts. It has been used to treat anxiety, insomnia, arthritis and gout. Celery seed in particular assists in the relief of symptoms of gout, arthritis and rheumatism.