When to Plant Tomatoes & Peppers
Every spring when the weather turns warm it can be tempting to jump the gun and plant our tomatoes and peppers too early. However, just because it is getting into the 60s, 70s, or even 80s during the day doesn’t mean that it is the right time to plant heat-loving vegetables like tomatoes and peppers. There are a couple of things to keep in mind – overnight temperatures and soil temperatures.
Even though the chance of a frost is fairly minimal after mid-April, we are still frequently getting down to temperatures in the mid-30s to mid-40s overnight. Tomatoes and peppers will not be killed by these temperatures, but they will be shocked and potentially damaged by exposure to those temperatures. Planting tomatoes and peppers without any protection from overnight temperatures will result in little to no growth until the weather is consistently warmer. Plants that are set out in early May will quickly catch up with plants set out earlier because of the difference.
Even more important that overnight temperatures is the soil temperature. The soil typically is slower to warm up than the air, and tomatoes and peppers need a soil temperature of at least 55 degrees F (and they really prefer 60 degrees F). Cold soil has the same effect (and sometimes a bigger effect) than cold air. Not only will the temperature shock the plants, it can also induce a phosphorus deficiency. If you observe a purple coloration to the leaves or stems of your plants, that is phosphorus deficiency. Usually it is not due to a lack of phosphorus in the soil but to the cold temperatures that prevent the plants from absorbing the phosphorus.
It is very easy to test your soil temperature to see if you are ready to plant. Just find a thermometer that will measure the right temperature range and stick the probe about 2-3 inches into the soil in late morning. This will give you a good average soil temperature in your garden.
Ways to Plant Earlier
Normally, I just wait to plant until the conditions are right in early May. However, if you want to plant earlier, there are a couple options. Many home gardeners like to use different types of water teepees to keep the ambient temperatures warmer around the plants. You can also choose to warm the soil by using clear or black plastic spread over the soil. Tomatoes and peppers can be planted right through the plastic. The warmer soil temperatures will enable the plants to grow more quickly in the spring.