Stable manures are undoubtedly the best fertilizers for celery, because they not only supply plant food, but also humus. Irrespective of soil type or location, all growers use manure if it can be obtained at reasonable prices. Horse manure is most generally employed, although cow manure is preferred by some gardeners. The amount of manure to the acre varies from 10 to 50 tons, Many of the most intensive growers, who figure upon gross returns of not less than $1,000 an acre, apply at least 50 tons, but excellent results may be secured with half this amount if supplemented with commercial fertilizers. Ten tons annually on muck lands may produce good results, but the largest profits are seldom, if ever, secured without the free use of stable manures.
Rotten manure is preferred by many growers while others make winter applications of fresh manures. When the latter plan is practiced the manure should be chopped up and thoroughly mixed with the soil by a disk harrow before plowing. The best results from rotten manure are obtained from dressings applied after plowing, the most approved plan being to spread broadcast. Formerly, many growers bedded the manure in trenches or furrows before planting, and some continue the practice. Mulching with manure is described later.
While some sections rely wholly upon stable manure, high-grade commercial fertilizers can always be used with profit. It is customary to use a large percentage of nitrogen. Four per cent can probably be used to advantage in all instances and 6 or 8 per cent would be profitable under certain conditions. Eight or ten per cent of each of the mineral elements should be used. An excellent plan is to use at planting a 4-8-10 fertilizer, and top-dress with nitrate of soda at intervals of two or three weeks to obtain additional nitrogen. The first application of nitrate should not be made until the plants are well established, and then 150 pounds an acre should be distributed along the rows. Two hundred pounds may be used at each subsequent application. Soft or pithy stalks are sometimes attributed to too much nitrogen. It is claimed that the free use of the mineral elements will counteract this effect, producing firmer stalks. Many intensive growers use two tons or more of high-grade fertilizer to the acre, while a ton is a common application, but inadequate for the largest returns.
As previously explained, plants for the early crop should not be set in the open until after danger of severe frosts. In most sections planting should not occur until May 10 or 15. Strong, vigorous plants properly set at this time should produce a marketable crop by August 1. The late plants may be set the latter part of June and throughout the month of July, depending upon variety, soil, weather and climatic conditions.
The ground should be fine, smooth and moist before transplanting is begun. It should also be fairly firm and marked at the required distances. Various forms of markers are employed, but shoe and roller markers are most popular. The roller markers may have pegs to mark the place for each plant, to secure uniformity in spacing. They relieve the foreman of the annoyance of looking after this matter.
Planting distances are extremely variable. If soil is to be used in blanching, the distance between rows must be not less than 3« feet; 5 feet is the more common spacing, especially for the tall green varieties. Sometimes an early variety, as Golden Self-Blanching, is planted in alternate rows. This variety is blanched by means of boards. The distance in this case need not be more than 30 inches. After the early crop is sold there is ample space to blanch the late crop with soil. When boards or other devices are used for blanching the spacing between rows varies from 18 inches to 3 feet. In the most intensive plantations where boards are used, the distance between rows is usually from 20 to 24 inches. The standard distance between plants in the row is 6 inches, although there is a decided tendency to plant closer. Some of the best growers plant the early varieties only 4 inches apart and allow 24 inches between rows. At these distances 65,000 plants are required for an acre.
Double row planting is practiced occasionally. With this method the rows are about 6 inches apart, and either earth or boards may be used in blanching.
When the plants are set very close together both ways, as 8 × 8 inches, or closer, the method is known as "the new celery culture." Like other intensive methods, it is adapted to only very fertile lands where the supply of moisture can be maintained. With this plan there are usually 5 to 10 rows in a bed with 2-foot alleys between them. When all the points are considered, it is better to plant 4 × 24 inches apart, so that a wheel hoe can be used in cultivating. Close planting is not so well adapted to the green varieties because of the greater difficulty in blanching.
Transplanting can be done to better advantage in humid or cloudy weather. The plants should be lifted with care. If the seed beds or flats are watered 24 hours in advance of planting, the plants can be removed with more soil clinging to the roots than if unwatered. Some growers give little attention to this matter and often shake most of the soil from the roots. In this case the roots are usually puddled before setting, or the ground may be watered before and after planting. Dibbers, trowels, or the forefingers are used in making the holes to receive the plants, which should never be set deeper than they stood in flats or beds. Pressing the soil firmly to the roots completes the operation of transplanting.