This section is from the book "The Standard Cyclopedia Of Horticulture Vol2", by L. H. Bailey. See also: Western Garden Book: More than 8,000 Plants - The Right Plants for Your Climate - Tips from Western Garden Experts.
The greatest care should be exercised in procuring seed, for inferior seed may result in pithy or hollow stalks, a poor stand of plants in the seed-bed, seedlings of low vitality, or a large percentage of seed shoots. Only the most reliable dealers, those who have a reputation for furnishing first-class seed of the varieties desired, should be patronized. To make certain of securing good seed, some careful growers import their seed directly from foreign producers, which, however, is unnecessary if the proper precautions are taken in the selection of a responsible seedsman. Practically all of the seed of the self-blanching varieties is grown in France, while most of the seed of green varieties is produced in California. As there is never absolute certainty of securing entirely satisfactory seed, some growers follow the excellent practice of buying in large amounts, sufficient to last several years. Only a small quantity of the seed is planted the first year to determine its real merit, and if found satisfactory there is sufficient quantity on hand to last several years.
If kept in sealed jars in a room where the temperature does not vary greatly, the germinating power will be retained at least six years.
Celery seed is very small. An ounce contains about 70,000 seeds, and with the very best conditions should produce at least half this number of plants. It is not safe, however, to count on a much greater number than 10,000 plants to the ounce, because many of the seeds usually fail to germinate and the plants at first are very small and easily perishable. The seeds are slow to germinate. They should be planted in fine soil which, if possible, should be kept constantly moist but never wet.
Seed for the early crop is seldom sown before the first of March. If checked in growth at any time, there is great danger of the plants producing seed shoots which renders them unsalable. Plants started the first of March will, with proper care, be ready for market in August. Earlier sowing is possible and sometimes desirable, but adequate facilities must be provided to avoid crowding the plants, which invariably results in checking the growth. Some gardeners have found it to be profitable to start the plants the latter part of February, finally transplanting into frames, where the crop is matured.
Seed for the early crop may be sown in the beds of the artificially heated frame or greenhouse. Many growers use flats or shallow plant-boxes, which are placed in the hotbed or greenhouse. While broadcasting of the seed is often practised, it is better to sow in drills 2 inches apart. The furrows should be very shallow, as the seeds should not be covered with more than 1/8 inch of earth. Muck mixed with a small amount of sifted coal-ashes, sand and a little bone-meal, is most excellent for starting plants under glass. After sowing and lightly covering the seed, place a piece of burlap over the bed, and water it. Keep the bed covered with burlap or a piece of cloth until the plants begin to come up. Do not water more than necessary to keep the bed moist. When the plants appear they will need plenty of light, sunshine and fresh air. A temperature of 70° to 75° is most favorable to germination, but 10° lower should be maintained if possible after the plants are up. Higher temperatures, however, will do no harm if the proper attention is given to ventilation.
When the rough leaves appear, the seedlings should be transplanted into beds or preferably flats, spacing the plants 1 1/2 inches apart each way. Stronger plants will be developed if they are set 2 inches apart. The flats may be about 2 inches deep and half filled with rotten manure, the remainder of the space being filled with good rich soil. The manure will furnish ideal conditions for the roots of the young seedlings and make it possible to transplant them to the open ground with blocks of earth and manure so that there will be practically no check in growth. If earliness is an important consideration, this method of treatment is highly important. Young celery plants require considerable nursing, and it will not do to take them from warm greenhouses or hotbeds to coldframes before the season is well advanced. They will suffer even more than tomato plants from low temperature. One of the most successful of our American growers invariably plants from the greenhouse to the open ground, beginning about May 10 .
Spraying the seedlings several times with bordeaux mixture may be the means of avoiding loss from fungous diseases.
Seed for the late crop should be sown in the open ground or in protected beds as soon in the spring as the soil can be prepared. Delay in starting the plants is often responsible for a failure of the late crop. It is not so easy to control moisture in the outdoor seedbeds. If overhead irrigation lines are available, there will be no difficulty in this matter. The beds are often shaded with brush or lath screen. Small beds may be kept covered with moist burlap. When starting on a large scale, the rows may be a foot or more apart. Thinning is often necessary to secure stocky plants. The plants may be set where they are to mature any time after they have attained a height of about 3 inches. Ordinarily seedlings started out-of-doors are transplanted directly to the permanent bed or field without an intermediate shift, although this is an advantage in developing stronger plants with better roots. If the plants attain a height of 5 inches or more before they are set in the field, the tops should be cut back before transplanting.