If you only ate one meal a week, do you think you would grow as tall as you would otherwise? How long could you last without water or air? We all have basic requirements necessary to maintain a healthy body. These include oxygen, water, carbohydrates, and other nutrients. Plants are no different. They require these things as well, and it is the job of the horticulturist to make sure that they get them.

We get our oxygen from the atmosphere. So do plants, but it must first diffuse into the soil because they respire or “breathe” with their roots. For this reason, there must be a balance of air and water in the soil. Many plants die from overwatering because they do not get enough oxygen. On the other hand, if the plant does not receive enough water, it wilts and eventually dies because it accesses nutrients from minerals dissolved in the water and because water is necessary for photosynthesis.

We get carbohydrates from eating plants. Plants, however, make their own carbohydrates with photosynthesis. Photosynthesis runs on solar energy, which is used to combine carbon dioxide and water into the sugar called glucose. It happens in the green-pigmented chloroplasts found in the parenchyma cells of leaves (Figure 4.1).

The duration and intensity of sunshine; the quality of the soil; and such environmental factors as temperature, annual rainfall, humidity, and wind are all variables that affect plant growth. As you may have noticed, not everyone requires the same amount of food or water. Also, some of us actually like cold weather, whereas others prefer the heat. The specific cultural requirements of a plant in a vegetable garden are different from those of a plant in the wildflower meadow, as are those that evolved in alpine versus tropical versus desert environments. Cultural requirements for sunshine, soil quality, water, and climate are described below.