Growing seasons in the United States are lengthening, offering both advantages and challenges for gardeners. The growing season is defined as the period between the last frost of spring and the first frost of fall, during which most plants grow. Since 1895, this duration has expanded in many states, providing more time for gardeners to cultivate vegetables and flowers. However, it also gives pests more time to thrive.

Analysis from The Old Farmer’s Almanac, America’s longest-running almanac, indicates a general trend of lengthening growing seasons across the U.S., predominantly in the West, parts of the Northeast, and some Southern states. According to the almanac, states such as California have seen their growing season lengthened by over a month.

Climate change is raising global temperatures and altering weather patterns, significantly affecting gardening. Data from Climate Central, based on NOAA records, shows that since 1970, summer temperatures have risen in approximately 97% of major U.S. cities.

States with Significant Changes

The almanac’s map, tracking changes from 1895 to 2023, reveals that California experienced the largest increase, adding about 47 days to its growing season. Washington saw an increase of around 40 days, while Arizona gained about 35 days and Utah added roughly 33 days. Other states like North Dakota and Wyoming also experienced significant extensions, each adding about 32 days.

The increased duration of growing seasons has not been uniform across regions. For instance, while Florida noticed a notable change, Alabama experienced almost no change, and Mississippi gained less than a day. Georgia was unique in facing a decrease in growing season length. Changes have been most pronounced in the West and Northeast, although some states like Rhode Island saw minimal changes despite regional trends.

Recent decades have shown the largest shifts, with global temperatures rising significantly. EPA data confirms that the most substantial increase occurred during the last 30 years of the study period.

Carlos Messina, a professor of predictive breeding at the University of Florida, stated that extended growing seasons can benefit those in northern Florida, although the region might also see more extreme weather, such as hurricanes.

Implications for Gardeners

Extended frost-free periods allow gardeners to pursue a broader range of plants. They can harvest tomatoes later in autumn and successfully cultivate heat-loving crops like peppers. These conditions also facilitate growing flowers or vegetables typically unsuited to cooler climates.

The USDA has noted that the shift in growing degree-days opens up opportunities to try new crops and markets. However, this longer season is beneficial only if temperatures stay within plant growth limits and if there is adequate water and nutrients without excessive disease pressure.

Messina warns that while some plants benefit from warmer conditions, others, such as those susceptible to heat stress or needing chilling hours, like apples, might no longer thrive. Higher temperatures could favor pests, requiring gardeners to be vigilant year-round.

The USDA further notes that longer growing seasons can support multiple insect generations, increasing resistance to insecticides over time, leading to a mixed bag of outcomes for gardeners.

Gardeners’ Adaptive Strategies

To counteract growing challenges, the almanac recommends several strategies. Gardeners should use row covers to protect young plants until pollination is needed. Regular inspection of plants for eggs and damage is crucial. Insects should be managed initially with physical methods, such as spraying aphids with water. Larger pests can be manually removed, and infected leaves should be dealt with promptly.

Beneficial insects are valuable allies. Gardeners should cultivate a mixture of flowers, herbs, and vegetables to attract these helpful species. Avoid using insect sprays unless necessary, as they can harm beneficial insects.

Messina suggests a strategic approach, including adjusting planting schedules and cultivating shorter-maturity plants to mitigate heat stress effects. Irrigation scheduling might also need revision to keep plants cool.

Adapting to a changing climate is challenging. Messina highlighted the need for balance in changing agricultural practices to avoid maladaptation while preparing for future conditions.