Celery and celeriac need an extremely rich moist soil with a pH of 6.0 to 7.0. Most home gardeners who grow celery buy 4 to 6-inch-tall seedlings; they can be planted when night temperatures are no longer likely to fall below 40 (lower temperatures make the plants send up inedible flower stalks instead of edible leafy stalks).

A good variety is Michihli. A loose- leaved type, B. chinensis, grows 12 to 18 inches tall and has edible greenish white stalks; a good variety is Crispy Choy. A 10-foot row yields about 12 heads over three weeks.

Chinese cabbage does best in soil with a pH of 6.0 to 7.5. The soil requires special preparation: dig a 2-inch layer of compost or a 4-inch layer of well-rotted cow manure into a strip 12′ to 18 inches wide and 8 inches deep, then add 1 pound of 10-10-10 fertilizer per 10 feet of row.

In most of the U.S. and southern Canada, where frost is expected in winter, sow seeds about three months before the first expected fall frost for harvesting in fall. In regions where winter temperatures rarely fall below 25, sow half the crop in fall to mature in the spring. If Chinese cabbages are sown in spring, they send up inedible seed- stalks as soon as hot weather arrives, even though the plants are young. To sow seeds, group three or four seeds in a spot, setting each group 1/2 inch deep and 3 to 4 inches apart in rows 18 to 24 inches apart. When the seedlings become 1 inch tall, pull out all but the best plant in each group.

When the plants become 6 to 8 inches tall, pull up every other plant, leaving a spacing of 6 to 8 inches. If the soil is very rich, the plants will become overcrowded. When they begin to touch one another, thin again for a final spacing of 12 to 16 inches.

Sow celeriac seeds indoors in regions where frost is expected in winter and outdoors in frost-free regions about 10 weeks before night temperatures can be depended upon to stay above 50. Celeriac matures approximately 200 days after seeds are sown. However, the root is edible at any earlier stage. To harvest celeriac, pull up the plants and cut off the tops; the tender roots may be stored in damp sand for several weeks.