Growing juicy, flavorful tomatoes starts with getting the soil temperature right. As heat-loving plants, tomatoes need warm soil temperatures to thrive at every stage – from germinating seeds to ripening fruit. By optimizing soil warmth throughout the season, you’ll be rewarded with sweeter, more abundant tomatoes.
Why Soil Temperature Matters for Tomatoes
Tomatoes require warm soil to grow vigorously and produce a robust harvest Cool soil below 60°F causes problems like
- Slow, uneven germination of seeds
- Stunted growth when transplanting seedlings
- Poor flowering and fruit set
- Delayed maturity and flavor development
Maintaining the ideal soil temperature in the 65°F to 85°F range allows tomatoes to progress smoothly through each phase of development. Here’s an overview of tomato plants’ soil temperature needs:
- Seed Germination – 70°F to 85°F for fast, uniform sprouting within 6-8 days.
- Transplanting – 65°F minimum, ideally 70°F overnight. Prevents shock.
- Flowering & Fruit Set – 65°F to 80°F for prolific blossoms and pollination.
- Ripening – 70°F to 85°F for even maturity and full flavor.
Check the soil temperature every day with a soil thermometer to make sure you know what the temperature is at the planting depth. Change the time and way you plant to keep the soil in the best temperature range.
Target Soil Temperature Ranges for Tomatoes
Let’s look more closely at each growth stage to get a better idea of what temperature tomatoes like in the soil:
Seed Germination – 70°F to 85°F
Soil temperatures should be between 70°F and 85°F for tomato seeds to germinate well. At these warm temperatures, seeds should sprout within a week. It takes 4-6 weeks for seeds to germinate in cooler soil at 50°F.
Seeds fail to emerge at all below 50°F and above 104°F. Use heating mats when starting seeds indoors to maintain ideal warmth.
Transplanting – 65°F to 80°F
Don’t move tomato seedlings until the soil temperature is at least 65°F during the day, and preferably 70°F or higher. At night, the temperature should stay above 55°F.
If soil is too cold, seedlings suffer transplant shock, showing stunted growth Maintain active root growth with adequately warm soil Row covers can provide extra warmth.
Flowering & Fruit Set – 65°F to 80°F
For prolific blossoms and successful pollination, tomato plants need soil temperatures between 65°F and 80°F. Shoot for nighttime lows above 55°F and daytime highs from 75°F to 85°F.
Extreme heat above 90°F disrupts pollination and causes flowers to blast. Provide shade and ample moisture to cool overly hot soil.
Ripening – 70°F to 85°F
Tomatoes require consistent 70°F to 85°F soil to ripen evenly with full flavor. Cooler temperatures delay maturity and affect taste.
Monitor soil moisture as well for proper fruit fill. Mulching moderates optimal warmth and moisture levels.
Adjusting for Regional Climate Conditions
When determining planting time, consider your local climate. In cooler areas, start seeds early indoors and use season extending covers. Wait for 55°F+ nights before transplanting.
In hot climates, provide shade and wind protection. Water deeply, and mulch to moderate soil temperature. Choose heat-tolerant varieties like Sun Master and Solar Fire.
The microclimate around your garden impacts temperature too. South facing beds warm faster while shaded gardens stay cooler in summer. Group tomatoes accordingly.
Tips for Controlling Tomato Soil Temperature
Here are some techniques for achieving ideal tomato soil temperature:
- Use black or red plastic mulch to absorb heat.
- Install cloches, low tunnels, or row covers to retain warmth.
- Mulch beds to stabilize soil temperature.
- Provide temporary shade covers during hot afternoons.
- Water early to prevent severe midday heat.
- Position plants to take advantage of sun/shade patterns.
- Select disease-resistant, heat-tolerant varieties as needed.
- Check soil temperature daily at 4 inch depth and adjust as needed.
Careful monitoring and adaptive gardening practices will maintain the properly warm soil tomatoes need from seed to harvest. Paying attention to temperature optimizes growth and results in your most bountiful tomato crop yet.
Ideal Soil Temperature for Planting Tomatoes
Soil temperature is another indicator of readiness. Planting in cold soil can result in generally stunted growth and nutritional deficiencies. Wait to plant tomatoes until soil temperatures have warmed to at least 60°F (16°C) – but ideally 65 to 70°F (18 to 21°C).
A finger stuck in the soil is a quick and easy way to tell if it’s warm enough to plant tomato plants. If you cannot keep your finger all the way in the soil for a full minute without feeling uncomfortable, the soil is most likely too cold for planting tomatoes. Of course, a soil thermometer helps too. ( credit: Getty s).
When to Plant for Your Area
Tomatoes are warm-season crops that grow in the spring and summer, with fruit production from summer to early fall, depending on the variety and your climate.
In warmer regions, tomatoes can be grown nearly year-round. Try planting tomatoes early in the spring and then again plant a second late-season crop of tomatoes in July to August.
- In the South, you can plant tomatoes in January and pick them in April or May.
- In places like the mid-Atlantic, you can plant tomatoes in the spring and pick them in late spring or early summer.
- In the Pacific Northwest, you can plant tomatoes in late spring and pick them in the summer.
- Tomatoes grow best in the Northeast and Midwest from late spring to early summer, and they should be picked from midsummer until the first frost in the fall.
Bear in mind some tomato varieties are more cold-hardy than others. The number of days until maturity, which is often written on the seed packet, will help you decide if a certain variety will grow well in your area.
Importance of Checking Soil Temperature Before Planting – Quick Tip
FAQ
What is the best soil temperature for tomatoes?
The second sign for knowing when do you plant tomatoes is the temperature of the soil. Ideally, the soil temperature for the best time for planting tomatoes is 60 F. (16 C. ). A quick and easy way to tell if the soil is warm enough for planting tomato plants is to thrust a finger in the soil.
Will tomato plants be ok in 40 degree weather?
Tomatoes can tolerate temperatures as low as 32°F, but thrive in temperatures above 50°F.
What temperature do tomatoes like at night?
Tomatoes require a minimum of six hours of direct sun daily. They prefer daytime temperatures of 70 to 80°F degrees and nighttime temps above 60°F. Jul 5, 2023.
How often should I water tomato plants?
Tomato plants typically need 1 to 2 inches of water per week, but the exact frequency depends on factors like soil type, weather, and plant size.