Is 46 Degrees Too Cold for Tomato Seedlings? (2024)

FAQs

Can tomato seedlings survive 45 degrees? ›

Low Temperatures

Although tomato plants can survive temperatures down to 33 degrees Fahrenheit, they show problems when temperatures drop below 50 degrees F, according to the U.S. Department of Agriculture Research Service.

Temperatures below 50 degrees Fahrenheit can prevent the seedlings from growing.

Tomatoes need to be kept well above freezing to survive. There's no point trying to put them outside – or even into a greenhouse – until your last expected frost date has safely passed. Temperatures below 10ºC (50ºF) can result in slow growth and problems with flowering and fruiting.

Tomatoes' Temperature Range

Although mature plants might survive light frosts, temperatures below 40 F damage flower and fruit production, making tomatoes perennial only in U.S. Department of Agriculture zones 12 and up.

Tomato plants are also susceptible to chilling injury at temperatures between 0 and 5° C. Chilling can cause stunted growth, wilting, surface pitting or necrosis of foliage, and increased susceptibility to disease. Low soil temperatures also stunt plant growth and prevent root development.

Low Temperatures

Temperatures below 55 degrees Fahrenheit are too low to grow a healthy tomato plant, says The University of Arizona Cooperative Extension.

Our recommendation would be to remove the cold protection covering once temperatures are above 32 degrees. If you leave the covering on when it gets warm and the sun is shining brightly, it may get too hot inside the cover and stress out the plants.

If you're wondering at what temperature threshold you should be bringing your plants, there's a short answer: when nighttime temperatures reach 45 degrees (F), it's time to bring your plants indoors.

To keep your tomato plants productive for as long into autumn as possible, they will need to be covered up each evening when temperatures dip below 50°F (10°C).

How do you know if a tomato plant is too cold? ›

Symptoms of Tomato Cold Damage

Newly transplanted tomatoes may have olive green and yellowing leaves, with a purplish underside. Leaves on more established tomato plants will turn black and wilt. These blackened leaves may be pinched off, but leaves that are still green will recover when warmer temperatures return.

Tomato plants are surprisingly resilient. Depending on the extent of the frost damage, your young toms may come back even stronger! If they are beyond recovery, replace them and know, you are not the first gardener to lose a plant or two to the weather.

An important temperature to remember: tomatoes can be planted in the garden when the soil temperature reaches 60 degrees Fahrenheit.

Seedlings, with their tender new leaves, often give up the ghost when temperatures dip to 32-33°F. Tropical plants have differing low-temperature thresholds. Some keel over when temps fall to 40°F; others crumble at 35°F. Other plants are just hardy by nature and can withstand temperatures as low as 18-20°F.

Tomatoes are warm-weather plants and are very fragile at this stage of growth. Hardening off should be done on clear or overcast days (no rain), when daytime temperatures are at a minimum of mid-50 degrees, with little to no wind.

Be sure to bring them in each night. And use those plant parenting instincts—don't put plants outside if temps are forecast to dip below 45°F, or strong winds or snow are expected.

The night time temperature should not go below 55 degrees Fahrenheit (13 degrees Celsius). Lower temperatures make your plant suffer, thereby stunting growth a bit.

Yes, 46F is cold to most people in normal circ*mstances. Room temperature is usually taken as 68F - 72F which is the range of temperature most people feel comfortable.

4) Using Bottom Heat for Seed Starting:

Tomato seeds should germinate within 5-6 days if you can keep the soil temperature around 80º F. Peppers take a little longer with a little higher temperature (7-8 days at 85º F).

In their native tropical growing range, tomato plants are perennials that live for many years. In cold climates, however, they do not survive winter outdoors because they are not frost-tolerant. Because of this, most gardeners grow tomatoes as annuals.

How do you keep tomato seedlings alive? ›

I did some research and found out that houseplants need to be taken indoors before overnight temperatures dip below 45 degrees. Most tropical plants suffer harm from temperatures below 40 degrees.

This varies by the specific plant, but in general, 32 degrees Fahrenheit will damage most frost-sensitive plants. Frost can form at higher temps, however, when the dew point drops below 45 degrees Fahrenheit.

When temperatures are consistently warm in fall and winter, take advantage and keep the plants hydrated. Avoid watering when temperatures are below 40°F or when sustained freezing temperatures are expected within 24 hours as this water will freeze and not be available to the plants.

So, keep an eye out for your local weather forecast and get your plant coverings ready when temperatures are forecast to dip to 32 degrees F and below.

You'll want to move your houseplants indoors before night temperatures get below 45°F. Any colder, and you're likely to see damage, especially on tender new leaves and stem tips.

Surround plants with water-filled bottles, which will absorb heat during the day then release it at night, warming the air around your plants. This is especially effective within a greenhouse, tunnel or cold frame. You can also fill plastic bottles with hot water on cold nights to protect seedlings.

WHEN TO BRING PLANTS INSIDE. As a general rule, tender plants should be brought in when nighttime temperatures are below 50 to 55 degrees F, even if they are hardy for your zone. A plant's roots are more exposed when planted in a container versus in the ground.

Drape clear plastic or garden fleece over recently sown blocks or rows of young seedlings. Individual plants can be protected with squares of plastic or fleece cut to size, or by using purpose-sold cloches. Alternatively, make your own from clear plastic drinks bottles.

Use a Cover to Protect Tomatoes

When frost or temperatures are in the forecast for overnight (mid-30s or even 40ºF), cover your tomato plants with clear plastic or a tarp. If you face an extended cold pattern, consider using quality frost protection regularly.

How do you protect tomatoes from cold nights? ›

Tomato seeds need bottom heat in order to germinate. If you have a seedling heat mat, place the tray on the mat, plug it in and leave it on until the seeds start to sprout. Some people place their tray on a warm spot on top of their refrigerator, or somewhere else warm in the house.

Tomato seedlings do not need heat after germination unless soil temperatures dip below 60°F (15°C). Tomatoes grow best when daytime temperatures are 70 to 85°F (21 to 29°C) and nighttime temperatures are 60 to 70°F (15 to 21°C), so seedlings will benefit from added heat in cold, wintry conditions.

Tomato plants can be placed outside once all risk of frost has passed, but they will do better if kept in a greenhouse or indoors overnight until the summer when daytime temperatures are no lower than 17C.

Plant tomato seedlings outdoors when overnight temperatures remain above 50 degrees Fahrenheit. Don't rely solely on the average last frost date, however. Generally, tomatoes can go outside about a week or two after the last frost in an area, but this isn't a strict rule. Weather conditions can vary from year to year.

It takes about six to eight weeks to produce transplants of tomatoes and peppers from seeds grown under indoor lights. ANSWER: It takes about six to eight weeks to produce transplants of tomatoes and peppers from seeds grown under indoor lights.

One of the odd things about seedlings is that, as much as almost all seeds need warmth and stable temperatures to germinate well, once they germinate (once leaves appear), they grow best in cooler conditions and actually prefer it when temperatures drop at night.

Slow growth: Have patience. When seedlings seem to be taking forever to grow, it is usually due to low temperatures or inadequate nutrition. Over-watering: Many growers harm their tomato plants by over-watering. Soggy soil may cause your tomato seeds to rot.

Brushing plants helps them grow stronger, stockier (though shorter), and more able to withstand transplanting into the garden. You can help strengthen a growing tomato plant by making it move! There are two ways you can give your tomatoes a workout: brush them and blow air on them.

Can tomato seedlings survive cold? ›

Sun-loving tomatoes can suffer outdoors during spells of cold weather, with ideal temperatures from 18-24°C and no lower than 13°C. If it is too cold there might be poor pollination, curling of leaves and the fruits might be scarred, with holes.

To keep your tomato plants productive for as long into autumn as possible, they will need to be covered up each evening when temperatures dip below 50°F (10°C).

Maintaining room temperature above 60ºF will get the job done, but there are also seedling heat mats, heat lamps and many other tricks that farmers and gardeners have concocted to speed up the process.

The temperatures at which tomatoes thrive are between 55 and 85 degrees Fahrenheit. Check plant tags for information on the varieties you plant, but by and large, tomatoes will not set fruit when temps hit 85 degrees, and may have trouble setting color in the heat.

When do you put a fan on seedlings? Immediately after seed germination, we begin to run oscillating fans on low over our seedlings.

Use a Cover to Protect Tomatoes

When frost or temperatures are in the forecast for overnight (mid-30s or even 40ºF), cover your tomato plants with clear plastic or a tarp. If you face an extended cold pattern, consider using quality frost protection regularly.