Weather Basics for Organic Gardeners

How cold it gets in Winter and how hot it gets in Summer can help you predict whether a particular plant struggles or thrives in your garden.

A plant that lives one year where winter temperatures ranges between -10F to 20F may live several years where winter temperatures never dip below 32F. If you live in a cold winter climate, you may be able to force an annual to survive a cold winter, but wouldn’t it be better to plant something that doesn’t need so much attention? Knowing your climate zone can help you select plants with more confidence.

Do You Know Your Climate Zone?

Hardiness is the indication of how low a temperature a specific plant can tolerate before it dies. Most garden centers, seed catalogs, or plant Web sites list the hardiness of a plant by listing the climate zones in which it is hardy.

Climate zones are based on dates of first frost and last frost each Fall and Spring, as well as the range of low Winter temperatures. The United States Department of Agriculture defines hardiness zones for the U.S. and Canada. You can use the interactive map at the National Arboretum Web site to identify your state and locate your own climate zone.

Because plants are affected by heat as well as by cold, a zone system that tracks high temperatures was developed by the American Horticultural Society for anyone wondering if their climate gets warm enough for a particular plant.

Sunset Magazine developed its own climate zone maps in the 1950s. Originally covering only the Western states, the Sunset zones are now applied to the entire United States. Unlike the USDA and AHS, the Sunset zones take into account multiple climate factors; length of growing season, timing and amount of rainfall, winter lows, summer highs, wind, and humidity.

Account for Microclimates, Too

Every garden has more than one climate. Just as mountains affect the amount of rainfall received by the land on either side of the mountains, your house, trees throwing shade, the closeness of a flower bed to a fence or foundation, and many other factors can affect the climate from one part of your garden to the next.

Once you find out your general climate zone, examine your garden for differences in light, water, and temperature. Where does the shade fall at different times of day? When rain falls, do some parts of your garden get more rain than others? How do driveways, sidewalks, walls, or fences affect the temperature of the air or soil in some beds?

Make a climate zone map of your own yard, and then make sure that the plants in each of these micro-zones are suited for the conditions.

Use Native Plants For a Perfect Fit

While many plants may grow well in your particular climate, you always have the most success using native plants. Whether trees, shrubs, or flowering plants, native plants are already adapted to your climate because they evolved in that climate. To learn more about native plants for organic flowering gardening, read Native Plants for the Organic Garden, How to Grow A Native Plant Garden, and Installing a Wildflower Meadow.