The most common climatic factor governing the ability to grow is the depth of cold. Other limiting factors are rainfall, length of the growing season, length of the day at a particular period in the plant’s development, high temperatures, humidity, and amount of light. Some climatic factors are beyond control, but the site, shape of the garden, soil composition, irrigation and nutrients added can be modified to aid plant growth.
Rainfall or the amount of water available to a plant is critical. Deserts devoid of plants because the climate of an area prevents rain. Even in areas of normally sufficient rainfall, the wise gardener will develop alternatives to rainfall so that plants may flourish even when the weather is dry. Bed planting with deep middles to hold water, home drip irrigation system and sprinklers can prevent disaster from occurring if the rainfall is insufficient.
Length Of Growing Season
The length of the growing season determines whether many plants will produce to their full capability. Cotton takes many months to produce a crop. Most tomatoes take about 90 days or three months to produce a crop. It is most important to understand the maturing time for each plant which we attempt to grow. No plant should be started so late in the season that it fails to mature and produce to our satisfaction before the end of the growing season.
Length Of Day
The length of the day (or night) has an important effect on plants. Have you ever wondered why Chrysanthemums bloom in the fall or Poinsettias bloom one year and not the next when grown inside the house? It is because some plants grow and set their bloom buds under a given number of light and dark hours. The Chrysanthemum has vigorous vegetative growth during periods of long days and sets its buds during periods of short days.
Poinsettias are similar. Their vegetative growth comes during long days, and they set their buds during short days. Since they are very susceptible to cold, they will not set buds or flower in the South before the frost in the fall kills the plant. They are grown as a house plant, but if they are given artificial light during the bud development time, the buds will not initiate since the plant’s vegetative growth cycle continues indoors.
High temperatures may be very detrimental to some plants. Peonies, lilacs, and some other plants do not grow well in the South. Often this poor growth is due not just to the heat on a given day but to the accumulation of days of high temperatures. High temperatures affect soil fungi, insects, and diseases also, which may prevent the proper growth of these plants.
Humidity is important in two ways. Very low humidity can retard plant growth by removing water from the plant faster than the roots have the ability to replace it. Santolina is a popular plant which is excellent for hot, dry locations in the garden but which will grow poorly and look very bad in the wetter, shadier areas where the humidity is too high.
There plants for shade and plants for sun. Nature has provided us with a range of plants for almost all conditions. If you are aware of the natural growing conditions each plant requires, you will have much better results. When Impatiens (sultana) are noted as shade plants, don’t put them in full sun. When geraniums or roses are said to require sun, don’t plant them in the shade.