This section is from the book "Commercial Gardening Vol4", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
For intensive culture such kinds as Chemin or Plein blanc dove (or Golden Paris) are favoured for early crops, while for succession White Plume (Plein blanc d'Amerique) or Pink Plume (Plein blanc a cotes roses) are used. The seeds are sown for early crops in January, and for later crops about the middle of March, in a temperature of 60° to 70° F., the young plants being stimulated to make good sturdy growth by careful syringeings, pricking out when large enough, and by proper ventilation. The Celery plants are useful for planting in succession on the exhausted hotbeds in April, May, and June, after such crops as Radishes, Carrots, Lettuces, Cauliflowers, and Turnips have been cleared. The earliest crops of Celery are blanched by placing dry leaves or litter between the plants, and mats are often thrown over the plants (being kept up by a stout board at each side) to hasten the process.