How to Choose the Right Bulbs for Your Garden

Though all bulbs share the same life cycle, different species of bulbs have different climate preferences and characteristics. These differences affect both which bulbs you should buy for your garden and where and when you should plant the bulbs that you do buy.

Climate Preferences

Bulbs have adapted to survive the temperatures in the regions where they grow natively. Different bulbs are described as being hardy to different temperatures. A bulb that can withstand temperatures of 10°F, for instance, is said to be hardy to 10°F. Only bulbs that are hardy to the lowest temperatures in your region will be able to live for many years in your garden. The most popular bulbs—crocuses, daffodils, and tulips—are hardy to harsh winter temperatures (such as those of the Northeast), but some other bulbs are not.

How to Choose the Right Bulbs for Your Climate

The easiest way to tell whether a particular bulb can grow in your region is to use the Hardiness Zone Map developed by the U.S. Department of Agriculture (USDA). This map divides North America into a series of 11 numbered zones based on average low winter temperature, with 1 being the coldest and 11 the warmest. Each bulb is assigned a number based on the coldest zone in which it could survive the winter. So a bulb that’s a 4 could survive the winter in zone 4 of the USDA Hardiness Zone Map, as well as in warmer (higher-numbered) regions.

To choose bulbs that can survive the winter in your region, you need to know the hardiness zone in which you live as well as the specific bulbs’ hardiness ratings, usually found on seed packets, in seed catalogs, plant encyclopedias, and at nurseries. For more on the USDA Hardiness Zone Map, see How to Choose the Right Plants for Your Climate in the Quamut guide to Gardening Basics.

Bulbs as Annuals

Just because a particular type of bulb won’t survive the winter where you live doesn’t mean that you can’t grow it. There are certain bulbs, such as tulips, that you can treat as annuals: plant them for a single growing season, enjoy their blooms, then pull them up after their blooms have faded away.

Hardy Bulbs in Mild Climates

Some bulbs require a prolonged cold period during the winter in order to sprout and flower the following year. For that reason, these bulbs won’t grow naturally in mild climates (zone 9 or above). If you live in a mild climate, you can still get these plants to grow by using a technique called pre-chilling. Even so, when buying spring-blooming bulbs, always make sure to find out whether they’ll need to be pre-chilled to grow successfully in your area.

Bloom Period

Bulbs are also often categorized based on the season during which they bloom:

Spring-blooming bulbs
Summer-blooming bulbs
Autumn-blooming bulbs

Generally, most spring-blooming bulbs are true bulbs, whereas summer- and autumn-blooming bulbs are a mix of true bulbs and other types of “bulbs,” such as corms, rhizomes, tubers, and tuberous roots.

Sun and Shade Preferences

Some bulbs prefer sun, but others can tolerate—or may even prefer—more shade. Based on their preferences for sunlight, bulbs can be divided into three categories:

Full sun: Sun-loving bulbs need at least six hours of direct sunlight per day. Direct sunlight means sunlight during the middle of the day, when the sun is at its most intense, without any filtering or dappling by branches or other intervening objects.
Partial sun: Light-shade or partial-shade bulbs need at least six hours of filtered sunlight per day, meaning sunlight that may be partially blocked by branches or other intervening objects.
Shade: Shade-loving bulbs thrive when they are in shade for much of the day and may even be damaged by too much direct sunlight.

When buying bulbs, make sure that the area in your garden where you plan to grow them offers the right amount of sunlight or shade throughout the day.

Moisture Preferences

Most bulbs prefer well-drained soil that gets a good amount of moisture—some bulbs will even go dormant if the soil is too dry. Other bulbs can not only survive drier climates but actually prefer them.

Soil Preferences

Most bulbs grow best in loamy soil—soil composed of an even mix of clay, sand, and silt—that drains well but also retains some moisture. However, some types of bulbs may also be able to survive in (or even prefer) other types of soil, such as sandier or siltier soil. Before buying bulbs, get a sense of the soil or types of soil found in your garden and then look for bulbs that will do well in those soils. (For more on the different types of soil and ways to improve your garden’s soil, see the Quamut guide to Gardening Basics.)

Acknowledgments & Disclaimer

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The Basics of Bulbs

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How to Buy Bulbs

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