Tomatoes and Timing

By Michael Rohwer

For the past few years, I’ve been growing vegetables in an open plot behind my house, much like my family did as I grew up. It was easy to know when to begin planting in Michigan. Once the snow was gone it was time to plant.

Now that I live in a warmer part of the country, I’ve discovered something: I’m not a very good gardener. Without the telltale snow to tell me winter is or is not here, I needed to seek advice from native gardeners to know when to plant my tomatoes or how long the growing season is expected to last. Both of these questions depend on when the last spring frost occurred and when the first fall frost comes. I asked my local garden store’s experts and turns out it’s all changing!

EPA’s Climate Change Indicators in the U.S. Report also shows that the final spring frost is now occurring earlier than at any point since 1895, and the first fall frosts are arriving later. So the length of the growing season in the U.S. is increasing at both ends. The average length of the growing season in the lower 48 states has increased by about two weeks since the beginning of the 20th century (see image 1) and the first fall frost has arrived about two days later (see image 2). Since my tomatoes need to be planted after the last spring frost, it looks like I’ll need to start planting them earlier and earlier.

This may seem like great news for tomato-lovers like me, but changes in the length of the growing season can actually have both positive and negative effects. Moderate warming can benefit crop and pasture yields in mid- to high-latitude locations, yet even slight warming decreases yields in seasonally dry and low-latitude regions. A longer growing season could allow farmers to diversify crops or have multiple harvests from the same plot. However, it could also limit the types of crops grown, encourage invasive species or weed growth, or increase demand for irrigation. It sounds like I need to keep a close eye on my garden to adapt to these changes!

About the author: Michael Rohwer is an ORISE Fellow supporting the communications team in the Climate Change Division within the Office of Air and Radiation. When he’s not pursuing a career in protecting human health and the environment, you can find him enjoying gardening and sports.