Experience counts for more than anything else in determining the proper dates for sowing different kinds of seed. A great many factors must be considered, but one of the most important is market conditions. When will a given crop be most likely to command the best prices, and how many weeks or months will be required to get the crop ready for that particular time? Weather conditions must be regarded. Lettuce, cauliflower, cabbage, onion, radish, spinach, and peas may be sown as soon in the spring as the ground can be prepared. This will not do for pepper, eggplant, tomato, bean, melon, squash and seeds of other tender plants, for these must not be planted in the open until the ground is thoroughly warm and there is no danger of frost.
It is always better to sow after rain rather than before, and this is especially true in the heavier soils. The soil soon bakes after a rain, and a hard surface crust is fatal to the germination of delicate seeds. Such crusts exclude air, and thus prevent the necessary physical and chemical changes in the soil, and make it difficult for the tiny plant to force its way through the soil to the light. If heavy rains fall soon after sowing, the crust can often be broken to advantage by rolling as soon as the ground is dry enough. It is usually desirable to sow in freshly stirred soil, because of better moisture conditions.
Many questions must be taken into account when determining the proper amount of seed to use on a given area. Among them may oe mentioned: (1) The viability of the seed or its power to grow. This should be previously determined, and the rate of sowing regulated accordingly. (2) The date of sowing. It may pay to take chances in planting some crops, as beans and sweet corn, before the ground is warm enough to make certain of a high percentage of germination. By using seed freely a good stand may be secured (3) The physical character of the soil. More seed should be used in heavy soils, because the percentage of germination will be necessarily less than in light soils. (4) The size or vigor of the young plants. Carrot and parsnip seedlings are very delicate and feeble; and many may be lost before they are well started. Therefore the safe practice is to insure a good stand by heavy seeding. (5) If to be transplanted, the time when this work will be done should be considered. The seed may be sown much more freely if transplanting is to occur in about three weeks from sowing. (6) The demand of the market. At times the market may demand small carrots, onions and other products, or exactly the reverse, and sowing must be regulated accordingly. (7) It is rather expensive to thin some crops. For example, the thinning of onions is very slow and tedious, and therefore great care should be taken to sow just the right amount of seed. (8) Ravages of insects. Insects are usually very destructive to certain plants, as melons and cucumbers, and by using plenty of seed there will be greater certainty of saving enough plants to make a satisfactory stand. It generally pays to use seed freely and thin when necessary.
This is an important operation in growing many garden crops, and it is often practiced in starting plants under glass, but more frequently in open-ground culture. Thinning is a process of selection; the weakest plants should be discarded, and only the most vigorous left to mature. This is one of the strongest arguments for thinning. Thinning secures a uniform stand. Because the operation is tedious and expensive successful gardeners endeavor to avoid it as much as possible by the even distribution of the proper quantity of seed.