How Late Is Too Late To Plant Tomatoes In Your Garden? Here's The Truth

Whether you got your garden off to a late start or are just hoping to multiply your harvest, you might find yourself wondering if it's too late to plant tomatoes. This is not a silly question to ask, since planting these summer veggies at the wrong time is one of the most common mistakes when transplanting tomatoes. However, the answer isn't a straightforward one, and it depends on both the length of the growing season in your location as well as the tomato variety you're hoping to grow. It may be too late for you by late summer, or you may have until the fall.

Tomato plants are cold-sensitive and will be killed by frost, so they can only be grown in the warm growing season between the last spring and first fall frosts. When gardeners plant tomato seedlings in spring, it's usually one or two weeks after the last local frost date, to get plants off to an early start. However, the best time of year to plant tomatoes also depends on local weather conditions. Daytime temperatures should be between 65 and 75 degrees Fahrenheit, with nighttime lows no cooler than 60. Likewise, the soil temperature is also important — for optimum production, it should be at least 60 and ideally closer to 65 to 70 degrees Fahrenheit. 

It's easy to measure the soil temperature with a soil thermometer or check an outdoor temperature gauge on a given day, but gardeners must still consider the looming risk of frost as well as the number of days to maturity before relocating tomato transplants to the garden. All of these factors will determine the latest possible date you can plant your tomatoes.

When determining whether it's too late to plant tomatoes in your location, you'll need to find out your first average fall frost date. You can find this date by using an almanac or entering your zip code into an online frost date calculator. Now count back from that date to the current date to find out how many frost-free days are left in your growing season.

Next, find the number of days to maturity for the type of tomato you want to grow. You can find this number by looking at the seed packet. The average range is 65 to 90 days, though some early varieties can be harvested in as few as 50 days from transplanting. If there are fewer than 50 days left in your warm growing season, it is likely too late to grow even these quick-maturing tomato varieties, like 'Early Girl'. Depending on your growing zone, that 50-day-until-frost mark could be anywhere from August to October. 

You can use these calculations not only when checking to see if it's too late to plant tomatoes, but also earlier in the growing season when using another of the handiest hacks to remember when growing tomatoes: staggering your harvest window. Keep in mind that the estimated frost date is just an average — sometimes frost comes earlier, sometimes later. So if the number of warm days you have to grow tomatoes is almost or just barely enough, you might consider taking measures to extend the growing season, such as using floating row covers.