It is seldom best to sow for the early crop before March 1 in most northern sections., If sown earlier, special care must be exercised to avoid checking the growth before the plants are set in the field, for the fact seems to be well established that any hindrance of growth in seed bed, cold frame or field will be likely to cause seed production the first year. As the plants cannot be set in the open with safety until after May 1, it is difficult to maintain an unchecked growth when the seed has been sown very much before March 1.
Celery seed, being very small and slow to germinate, must be provided with the best conditions in the seed bed. The soil should be fine, moist and not given to baking. Muck is excellent when available. It is improved by the addition of finely sifted coal ashes, some sand and a small quantity of bone meal. If muck is not at hand, use any rich garden soil to which has been added liberal amounts of sand and fine rotten manure.
The seed may be sown in flats or in the soil of the hotbed or the greenhouse. If flats are used, the soil must be moist and well firmed, especially in the corners and along the sides. The seeds are sown thinly in rows 2 inches apart. The furrows are made very shallow, so that the seeds will not be covered with more than 1/8 inch of soil. After the seed is covered a piece of burlap is placed over the flat or the bed and the soil moistened by sprinkling the burlap. If possible, a temperature of about 70 to 75 degrees is maintained until the plants are up. The plants must then have plenty of light, sunshine and fresh air. They should be watered as often as necessary to keep the soil moist, but overwatering must be avoided. Many gardeners cover the beds with cloth while the seeds are germinating. It is an advantage to water between the rows, and thus the foliage is kept dry. The soil should also be stirred occasionally, and the temperature kept sufficiently high to maintain a healthy, vigorous growth. Thinning is done if the plants stand too close together.
When losses have previously occurred from damping-off fungi, the only safe course is to sterilize the soil with steam or formaldehyde. When the latter is used, a mixture of 2 pounds of formaldehyde with 5 gallons of water will give good results. Some growers also sterilize the seed by placing it for a few minutes in a solution made by adding 2 ounces of copper sulphate to 1/2 gallon of water. The seed should be dried thoroughly after this treatment.
When the rough leaves appear, the tiny seedlings are transplanted into flats or beds. An inch and one-half each way is generally ample space, and some growers plant only 1 1/4 inches apart, but if to be held for a longer period than usual, plant 2 by 2 inches apart. Before planting, the flats should be about half filled with rotten manure and then completely filled with a good garden soil containing plenty of rotten manure and some sand if available. The boxes should be kept in the hotbed or the greenhouse until the plants are well established and are making a vigorous growth. Then if the weather is not too cold, they may be taken to the cold frame. This transfer is a critical operation, unless proper care is exercised in providing the right temperature. Young celery plants require about as much heat as tomato seedlings. A desirable precaution against fungous diseases is to spray with bordeaux mixture before taking to the cold frame as well as to the open ground.
Seed for the late crop is usually sown in the open or in protected beds as early in the spring as the ground can be prepared. A moist seed bed is very important. Fall plowing will assist in securing the proper supply of moisture. There are various methods of starting plants out of doors, but if the fundamental principles are understood, there should be no trouble in getting a good stand of plants. There must be a full supply of moisture for not less than two weeks, and the soil must be sufficiently friable to permit the delicate plants to push through to the surface. A liberal proportion of humus will make conditions more favorable.
The land is often thrown up into beds, although this is unnecessary in well-drained gardens. Sowing in drills is much better than broadcasting, because the soil may then be cultivated. The seeds should have a slight covering of fine soil and the beds or rows watered, if necessary. The overhead system of irrigation is especially valuable in starting celery plants in outdoor seed beds.
In some sections it is necessary to start the plants for the late crop in beds protected by board windbreaks and by cloth coverings. In other sections, when the sun is particularly hot, cloth or lath screens must be provided to shade the plants until they are well established.
The rows are generally I foot apart. This provides plenty of space for wheel hoe cultivation until the plants are transplanted. The usual practice is to transfer from the seed bed to ground where the crop is to mature. Some growers prefer to transplant once before setting in the field, and thus secure stronger and more vigorous plants. When this intermediate shift is not made, the plants should be thinned to induce stockiness.
In the North new muck land is usually plowed and sometimes subsoiled in the fall. The winter exposure to frost improves the structure and prepares the soil for cropping the next year with corn or some other cultivated crop. In most instances, celery should not be planted until the second year. Whatever the character of the land, early plowing is important.
Sandy loams and heavy soils require frequent and thorough harrowing. A smoothing harrow and a plank drag or leveler should be used to make the soil fine and smooth before planting.
In making plans for the fertilizing of this crop the grower should bear in mind, (1) that the plants are shallow rooted; (2) that they prefer soils abounding in vegetable matter; (3) that rapid growth is essential to high quality, for plants which grow slowly are not so crisp, sweet and tender.
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.