Plants have evolved all over the world, adapting over the course of time to local conditions, whether temperate or tropical, wet or dry, loamy or rocky, sunny or shady. Plants that failed to find a niche became extinct and vanished. These days, we bring plants from diverse climates and communities into our gardens. Even when we try to design with native plants, we know that they, too, have diversity in their history. Their seeds may well have been brought to the region hundreds of years ago by animals, water, wind, and native people. Each plant species has a range of conditions under which it will thrive, other conditions under which it will merely survive, and unique limitations that will cause its death in hostile conditions.
Heat and cold influence plant survival. Understanding temperature in your garden will help you find the varieties of plants that can thrive for you, especially those plants that normally live for more than a year. Conditions in your garden are influenced by your region's climate, including frost dates, and your garden's unique exposure. Plants can be grown outside their natural climate if you provide warmth to tropical plants in winter (for example, growing a lemon tree in a greenhouse in Massachusetts) or cold to plants from temperate climates in winter (for instance, treating tulip bulbs with weeks of refrigeration before planting them in Georgia). Consider both heat tolerance and cold tolerance before your select your plantings.
Some regions, such as the Midwest, are hot in summer but icy cold in winter; some are either hot or cold all the time; and others are mild or moderate most of the year. In some regions, summers are very dry but winters are wet. Others are changeable from year to year. Even though we cannot do much about local weather, we can observe its patterns and choose plants that are naturally suited.
Within every garden, you can find areas with different kinds of exposure to the elements. These are called microclimates. Even a small deck will usually have several microclimates. The part closest to the house may get more reflected light if it faces west or more shade if it faces north compared to other parts of the same deck. In larger areas, differences are even more pronounced.
Within these special niches, some plants may bloom earlier or longer into the season or be more likely to freeze or overheat. South-facing slopes or sides of buildings tend to have a longer growing season than nearby areas. Spring flowers there may bloom a week or two earlier than those in a cooler part of the garden. Although a south-facing area may be warm on sunny winter days, the rapid drop in temperature from a bright winter day to a cold night may be too extreme for some plants. The cooler, shadier, north-facing exposure is better for marginally hardy plants and those that are prone to drying out in winter.
How windy is your garden? Strong winds can snap off branches and cause plants to dry out faster than they can take up water to replace its loss. When selecting plants for windy areas, try varieties that originated in windy climates because they have developed resistance through strength and flexibility. Leathery, stringy, or waxy leaves are another adaptation. Protection from wind may be needed for other garden plants. Windbreaks, walls, buildings, and berms (raised mounds of earth) help alter wind patterns in your garden.
The USDA's hardiness zone map shows the hardiness zones for the United States and Canada, which will help you chose the right plants for your climate. Go to the next page to see the hardiness zone map.
Looking for more information about gardening? Try these:
- How to Start a Garden: Find out how to get your garden started.
- Planting a Garden: Once the planning is done and the soil is ready, the next step is planting your flowers or vegetables.
- Annual Flowers: Learn about annual flowers, which continue to bloom throughout the growing season.
- Perennial Flowers: Find out about perennial flowers, which return to grace your garden year after year.
- Gardening: Learn the basics of successful gardening.