How to Grow Seakale
This Cruciferous perennial is a British native which is grown for the petioles which, after blanching, are white and succulent; unblanched they have a bitter taste. It is, sadly, little grown today in comparison with its former popularity.
The principle of cultivation is to grow a good, strong crown which can then be forced in the winter and spring in the open or in heated sheds or houses, to produce the 12 to 20-cm (5 to 8-in) long blanched leafstalks. Seakale is boiled like asparagus and has a crisp, nutty flavour.
Soil and fertilizer requirements
The pre-planting preparations forshould be similar to those made for . Well-drained, sandy loams are best, however, if the crowns are to be lifted in the winter for indoor forcing. This crop does not like acid soils so liming may be necessary but this will also help to reduce the likelihood of club root attack.
Like rhubarb, seakale can be propagated from seed but it takes at least two years before forcing-sized crowns are produced. Seedling variation also occurs and not all plants are identically suited to forcing. It is better, therefore, to propagate the crop vegetatively either by division of existing crowns or by(thongs). Buy crowns from a reliable stockist or from a known source. Root are taken from the main root mass when it is lifted for forcing. Pieces of lateral root which are 0.5cm (1/4in) thick and 15cm (6in) long are ideal for this purpose. Trim the end which was nearest the crown with a horizontal cut and the other end with a slope.
Bundle the cuttings together and heel them in under a cold frame during the winter. By the spring a number of adventitious buds will have formed on the flat tops of the cuttings. Remove all but the strongest before planting. One year is needed before the crowns will be large enough to force.
Planting and crop management
Grow seakale at a spacing of 60cm x 60cm (2ft square) and plant the divided crowns or root cuttings about 5cm (2in) below thesurface. The management of seakale during the vegetative growth stages is, once again, very like that of rhubarb. Weed control; flower stem removal; watering (where necessary); top dressing and mulching are all required if strong crowns are to be built up. Forcing
This, too, is similar to rhubarb and can be done either in situ or in heated buildings. In the former method pots or boxes are placed over the seakale crowns in late winter. Light must be excluded and the temperature inside can be raised by covering the forcing container with fermenting organic manure. For forcing inside the roots must not be lifted until they have received about a month of cold weather to meet the dormancy-breaking requirement. This means that the first forcing will not begin until late November.
Lift and trim the roots sufficiently for 2 or 3 to fit into a reasonable sized tub or box. Workaround the roots and settle them in with a thorough watering. Stand the containers in a heated shed or greenhouse with a temperature of 10-13°C/50-55°F. Much higher temperatures cause thin, weak petioles to develop. Cover the containers with tubs, pots, boxes or black polythene to exclude all light. Water as needed.
More roots should be lifted and brought inside for forcing until February. Forcing will take up to 6 weeks—at the temperatures mentioned—for the earliest liftings but considerably less time in the spring. Roots which have been forced inside are of no further use and should be thrown away. Complete destruction is difficult as they are so easily propagated from root cuttings. Crowns which have been forced in situ should be cleaned up, mulched and top dressed through the next growing season ready for forcing again next year. Strong, healthy crowns may be forced for at least five consecutive seasons.
Cut the blanched petioles when they are 15 to 20cm (6 to 8in) long.
Pests and diseases
Pests are rarely a problem but club root—the same fungus which attacks brassicas—can cause problems especially on acid soils. The presence of violet root rot is indicated by purple fungal threads on the roots while black rot causes the centre of the crowns to rot thus making them useless for forcing.
There are no named varieties of seakale.