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 ⅛ 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 « 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 1¾ 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.