How to Grow Celery

Botanical Name: Apium graveolens var. dulce

Plant Type: Hardy Biennial

Celery is a versatile vegetable for the home gardener – depending on how you grow and harvest it.  When picked as an entire vegetable, celery is all about its long, crunchy fluted stems which can be eaten raw and used for dips. When harvested stem by stem, celery is green, peppery, and perfect for soups and stews. Like celeriac, it is high in potassium and its diuretic properties can assist in cases of high blood pressure and joint complaints. When grown for fresh use, stems are blanched (wrapped and covered to preventing sunlight from colouring the stems), but self-blanching varieties are also available. Celery needs constant moisture and some shade in hot areas. Plant in blocks and mulch well.

Celery is a member of the plant family Umbelliferae (producing flowering umbels), its most familiar relatives being carrot, parsnip, dill, and coriander. Wild celery is a biennial, native to the old world and is a bitter aromatic plant once used by the ancient Greeks for medicinal purposes however, through selective breeding throughout the 16^th century, the bitterness was removed and the pleasant tasting, that crunchy peppery celery we now grow spread throughout the world.

Varieties

Celery varieties are classified into three distinctive groups, the familiar stem celery; celeriac (Apium graveolens var. rapaceum), which produces large edible roots up to the size of a large fist; and the leaf or soup celery (Apium graveolens var. secalinum) grown for its leaves, which are used as herbs or garnishes.

Our discussion here will be limited to the stem type. Stem celery varieties are classified as blanching or non-blanching types, because in many old varieties production of light-coloured stems, free of bitterness, required the progressive burying of the stems up to the leaves prior to harvest. For this reason, non-blanching varieties are sometimes referred to as trench celery.

Most varieties of celery available in this country are of the blanching type, though many gardeners still bury the stems to improve appearance and flavour. Varietal selection is very limited in Australia, with choices primarily being made for climatic reasons. Bolt-resistant varieties are particularly suited for cooler climates.

Cultivation

Celery can be sown or transplanted from spring to late summer in temperate regions, and in cold areas is best established during late spring. Some care has to be exercised in establishing plants too early as young plants are frost sensitive, and a sudden cold snap producing temperatures below 10°C can induce plants to bolt prematurely. Add a thick mulch of organic matter around the base of the plants to help conserve moisture, insulate the roots and suppress weed growth. Celery is a shallow-rooted plant with a high demand for water and nutrients so maintain watering as celery does not like to dry out

Growing celery in partial shade can improve the quality of the plants.

The traditional method for growing non-blanching varieties is to construct a trench 30 cm by 40 cm deep into which seedlings are transplanted. As the plants grow, the trench is progressively filled with soil to cover the stalks. Alternatively, gardeners can hill up around the stalks of plants on flat beds as they grow. Surrounding the stalks with soil can make plants more prone to a number of fungal and bacterial diseases, so some gardeners blanch stalks by surrounding them with tubes made of newspaper or brown paper up to one month prior to harvest. Blanching varieties can be improved in quality by hilling up soil or surrounding the stalks with hay.

Close planting in blocks acts as a partial blanch and is probably the easiest method to employ for blanching types.

Sun: Full sun – Part shade

Pollination: Insect pollination

Soil: Celery has a high demand for nutrients such as nitrogen and potassium, so potash or ash should be incorporated into beds prior to planting. The addition of aged manure is also an important part of bed preparation.

Growing from Seed

Sow: either sow direct into well prepared soil or sow into seedling trays for transplanting into the garden or larger pots when hardened off

Ease of Germination: Easy

Germination Temperature:  7-18 degrees C

Germination Time: 12 days

Spacing: Transplant 15-25cm apart

Harvest: 170 days

Yield: 1.1kg per plant

Seed germinates over a wide temperature range, and seedlings will emerge in about 12 days at 15°C. While celery transplants reasonably well, stress during the establishment phase can induce them to bolt.

Plants should be spaced at intervals of about 25cm, though some gardeners have them closer at about 15 cm, in order to produce smaller but more tender stalks. Celery should be grown in blocks rather than rows.

Maintenance and Care

Celery has a shallow root system, so care should be exercised when weeding around plants to avoid root disturbance. Mulching will help to reduce competition for resources and water.

Companion Planting

Good companions: Beans, cabbage, capsicum, cauliflower, cucumber, dill, leek, lettuce, spinach and tomato.

Bad companions: Parsnip and potato.

Pests and Diseases

Celery is fairly trouble-free but watch out for slugs and snails early on. Slugs and snails can cause considerable damage to young plants, so the use of baits or beer traps is recommended when these pests are a problem. Stalks and leaves can be affected by leaf spot and several fungal diseases, particularly in wet and humid conditions. If necessary, they can be controlled with copper-based sprays.

Container Gardening

Celery can be grown in pots, but it is best to use plastic or glazed ceramic pots, rather than terracotta because they are so water sensitive. Growing in pots does have the added benefit of making it very easy to blanch stems by wrapping in them a milk carton or other non-transparent wrap.

Harvesting

Celery stalks can be continually harvested from plants once they have reached a desirable size, and production can continue until very cold weather occurs.

Seed Saving

Seed longevity: 3-6 years

Isolation Distance: 800m

How to Save Seed: Allow a few plants to run to seed. This will occur in the second year, during summer, after at least 10 weeks of temperatures between 4-10 degrees C. Harvest plants as the umbels begin to brown, carefully placing the flowering (seed stalks) inside a pillowcase to catch the seed as it dries. Once dry, the seed is easily removed from the stems and is ready to store or replant.  

Tips and Tricks for Success

• Planting close together like will create a lot of shade between plants and help the stems to blanch.
• always keep celery well-watered, which will reduce the risk of plants bolting or stems turning stringy.
• in areas with mild winters, celery can be over-wintered in the ground by hilling up soil around the stalks and mulching with hay for protection from light frosts.
• celery needs lots of water to be crunchy and refreshing. Water regularly throughout the growing season. An irrigation system or wicking bed is ideal for this thirsty crop.