When it comes to planting tomatoes – there is one big mistake that stands far above all other miscues when it comes to getting your plants off to a fast start and keeping them healthy and productive – and do you ever need to avoid it! Unfortunately – many gardeners make it each and every year.
One thing is for sure, every gardener looks forward to planting tomatoes. There’s just something about those first warm days of spring that makes us eager to dig in the dirt and get a head start on the growing season.
But when it comes to tomatoes, jumping the gun can be one of the biggest miscues you can make. In fact, as it turns out, planting your tomatoes too early and before the soil gets warm enough is a surefire way to slow their growth, weaken their health – and invite a host of problems that can plague them all season long!
The Big Tomato Planting Mistake – Planting In Cold Soil!
If you’ve ever put tomato plants in the ground too early, you may have noticed they just kind of sit there. They don’t grow much. Even worse, their leaves often start to look yellow. The end result is that they still look the same size two to three weeks later – and far less healthy than when you first planted them.
Why? Because tomatoes hate cold soil. Many gardeners center their concern around trying to plant after the last expected frost date. While it’s important to avoid frost, what really matters even more is the temperature of the soil tomatoes are planted in.
As you will see below, allowing the soil to first warm up can make all the difference between a slow, disappointing crop – and a lush, productive tomato patch!
The Right Soil Temperature Matters – More Than You Think!
Tomatoes are a warm-weather crop. In fact, they originated from tropical and subtropical regions. Because of that, they thrive best when air temperatures and the soil temperatures are both warmer.
So how warm should the soil be before planting? The minimum soil temperature for planting tomatoes should be right around 60°F. Ideally, however, the soil should be somewhere between 65°F and 70°F at planting time. Anything below that, and the plant’s root system will struggle to develop properly.
Why Planting In Cold Soil Is A Big Mistake With Tomatoes
When tomato roots sit in cold soil, they can’t take in nutrients efficiently. Growth slows to a crawl, and the plant focuses all of its energy on survival instead of thriving.
In cold soil, the roots often stop growing entirely, waiting for the soil to warm up. This, in turn, delays everything – from flowering to fruiting, and your overall harvest. Even worse, stressed-out tomato plants are more vulnerable to pests and diseases.
Cold-stunted plants are like magnets for trouble, from fungal infections to pest infestations like aphids or cutworms. Last but not least, if there is a late cold snap – the already cold soil can frost and freeze even faster! In the end, planting early for a fast start often ends up doing more harm than good.
Letting Your Soil Heat Up
Tomatoes won’t die from being planted in 55°F soil, but they certainly won’t thrive. Just because the daytime highs are in the 60s or 70’s doesn’t mean your soil is ready.
For more on tomatoes – listen below to our podcast below on how to fertilize for success!
Keep in mind that soil warms much more slowly than air. You might have a string of sunny afternoons, but the soil a few inches down is still chilly, especially after a cool night. That’s why it’s so important not to go by feel, guesswork, or the calendar alone.
Some years spring comes early, other years it drags its feet. But the best way to know for sure is to use a soil thermometer! Affiliate Link: 4-in-1 Soil Temperature / pH / Moisture / Light Meter
A soil thermometer is one of the best inexpensive tools a gardener can own. You can find them at most garden centers or online – and they take only seconds to use. And do they ever keep you from making the big tomato planting mistake of putting your plants in too early!
To get an accurate reading, simply push the thermometer 3 to 4 inches into the soil. This is about the depth where your tomato roots will start growing.
It’s important to always check the temperature in the morning, since that’s when the soil is coolest. You’re looking for a consistent reading of at least 60°F, and ideally closer to 65°F or above for optimal planting.
Helping Your Soil Warm
If the soil is still too cold, it’s simply better to wait. Give it a few more sunny days, or consider warming the soil artificially. Some gardeners use black plastic mulch or row covers to help trap heat and bring the soil temperature up a bit faster.
Even though it might seem counterintuitive, planting tomatoes later, once the soil has warmed, often results in faster growth and earlier fruit than planting them early into cold soil. Remember that the sooner the roots take hold, the sooner the plant can grow upwards, start flowering, and begin setting fruit.
Plants that are put into warm soil grow rapidly, with lush foliage and strong stems. They’re better able to fend off pests, bounce back from wind or transplant shock, and are much more likely to produce a heavy yield.
In contrast, early-planted tomatoes often fall behind and take weeks to catch up. That is – if they ever do at all!
A Few Other Big Tomato Planting Mistakes To Avoid
Once you’re confident your soil is warm enough, here are a few other planting tips to make sure your tomatoes get off to the best start possible:
Harden Off Your Plants
If you’ve grown your tomatoes from seed indoors or purchased them from a greenhouse, take a few days to harden them off before transplanting. Gradually introduce them to outdoor condition. This helps prevent transplant shock and strengthens the plants. See: How To Harden Off Tomato Plants Before Planting.
Plant Deep for Strong Roots
Tomatoes can develop roots all along their stems, so plant them deep. Bury two-thirds of the plant, removing the lower leaves if necessary. This encourages a stronger root system, which means better support and more access to nutrients.
Water Deep and Mulch Well
After planting, water your tomatoes deeply to encourage roots to grow downward. Once they’re settled in, mulch around the base with straw, compost, or grass clippings. Mulch helps regulate soil temperature, keeps moisture in, and reduces competing weeds.
Stake Or Cage Early
Last but not least, support your plants right from the start. Install stakes, cages, or trellises at planting time so you don’t disturb the roots later. Proper support keeps fruit off the ground and reduces the risk of rot or pest damage.
Here is to letting your soil warm up – and avoiding the big tomato planting mistake of planting too early!
Simple Garden Life
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Simple Garden Life is a website dedicated to keeping gardening fun, simple and enjoyable! We publish two new articles each week along with a new garden podcast episode every two weeks. This article may contain affiliate links.