Celery is not the easiest crop to grow, although self-blanching varieties, which do not need earthing-up, have made growing celery less laborious. Traditional or Trench varieties are earthed up not simply to whiten the stalks but the process of drawing the celery up to the light improves the flavour and reduces the stringiness.
Self-blanching varieties are therefore somewhat inferior in taste and crispness to traditional trench varieties and they cannot be left in the ground during frosts but they do make celery growing more accessible to all gardening skill levels.
Soil & Growing Position
Choose a sunny spot and for self blanching varieties, dig in some manure in the spring in a block approximately one metre square. Alternatively, celery can be grown in a raised bed, once again mix in plenty of manure into the soil. By planting close together in a block, the celery is drawn upwards by the lack of light, making them more tender. Trench varieties, as their name suggests, need to be grown in a 'celery trench' which should be prepared in April and allowed to settle prior to planting. Prepare the trench in the following way: Dig a trench 15" wide, 12" deep and fork the bottom of the trench. Add a layer of manure in the bottom followed by layer of soil up to 3" below surface level. Prior to planting, rake in a general fertiliser.
Sowing from Seed
Celery seed is the smallest seed of all vegetables and can be very slow to germinate, taking up to three weeks, which is a good enough reason to buy seedlings. Sow seed between mid-March and early April in seed trays or in pots using a fine seed compost. Sow thinly over the surface and lightly press down with a seed tray tamper. Do not water from the top but rather by filling a container with water and then placing the seed tray in it, allowing it to suck up water from underneath. Then cover with a thin layer of vermiculite and put in a heated propagator until the seeds have germinated. Checking daily to ensure the compost doesn't dry out and water accordingly. Remove from the propagator once the seeds have germinated.
Growing on & Young Plants
Transplant into 3" pots or cells once the seedlings when large enough to handle and have formed some proper leaves. Once the plants are around 8cm tall, they can be planted outside but will need hardening off first by putting in a coldframe. Plant out at the end of May to early June. Plant self-blanching varieties 8-9" apart in a block and trench varieties 9" apart in the trench and water in very well.
Crop Care
Trench varieties will need blanching in August, once the plants are around 12" high. This is acheived by removing any side shoots, putting newspaper around the stalks and tieing loosely. Then fill the trench in with soil. In late August, moist soil should be mounded up against the stems and again in September, leaving only the tops of the foliage visible, being careful not to drop any soil into the celery hearts. Cover the foliage tops with straw or fleece if a frost is forecast.
Water regularly and thoroughly, particularly during dry weather as celery is essentially a bog plant, meaning that it enjoys constant moisture. Feed with a liquid feed during the summer. Once the plants have become well established, apply a light dressing of a high nitrogen feed such as Dried Blood and this will help improve crops.
Harvesting
Harvesting begins between August and October and continues up to the first frosts for the self-blanching varieties. Start with the outer plants, lifting with a trowel and being careful not to damage the surrounding plants. Trench varieties grown for winter use are ready from October onwards, up to Christmas for white types whilst coloured varieties will run into January.
