Landscape-gardening, like architecture, has developed intoll as the artist makes them on canvas, but uses natural objects in his pictures instead of paint and canvas.
=Market-Gardening.= Formerly market-gardening was done on small tracts of land in the immediate vicinity of large cities, where supplies of stable manure could be used from the city stables. But with the great increase in the population of the cities, these small areas could no longer supply the demand, and the introduction of commercial fertilizers and the building of railroads enabled gardeners at great distances from city markets to grow and ship their products. Hence the markets, even in winter, are now supplied with fresh vegetables from regions where there is no frost. Then, as spring opens, fruits and vegetables are shipped from more temperate regions. Later vegetables and fruits come from the sections nearer the great cities. This gradual nearing of the supply fields continues until the gardens near the cities can furnish what is needed.
[Illustration: FIG. 82. STRAWBERRY-GROWING IS AN ART]
The market-gardeners around the great Northern cities, finding that winter products were coming from the South and from warmer regions, began to build hothouses and by means of steam and hot-water pipes to make warm climates in these glass houses. Many acres of land in the colder sections of the country are covered with heated glass houses, and in them during the winter are produced fine crops of tomatoes, lettuce, radishes, cauliflowers, eggplants, and other vegetables. The degree of perfection which these attain in spite of having such artificial culture, and their freshness as compared to the products brought from a great distance, have made winter gardening under glass a very profitable business. But it is a business that calls for the highest skill and the closest attention.
[Illustration: FIG. 83. SETTING PLANTS IN A COLD-FRAME]
No garden, even for home use, is complete without some glass sashes, and the garden will be all the more successful if there is a small heated greenhouse for starting plants that are afterwards to be set in the garden.
=Hotbeds.= If there is no greenhouse, a hotbed is an important help in the garden. The bed is made by digging a pit two feet deep, seven feet wide, and as long as necessary.