It was painful to see my tomato plants suffer the devastating effects of frost after a cold night. I decided to go some research if I could save my tomato plants and help them recover from the frost.
Even if you are someone who lives in an area that is warm most of the year, you most likely still experience periods of frost in the fall while your tomatoes are still producing.
Tomato plants cannot recover from frost if the plant and fruits are frozen. They can recover from the frost if frost is mild or the temperature just dropped for a short period of time. You need to immediately spray them with water and prune the frozen parts so the plant can recover.
I’ve written a lot more details about my research in the article below. You will find useful tips on how to save your tomato plants from the frost. It will also give you some insight into how to protect both young and mature plants from frost in the future.
Diagnosing Frost Damage to Your Tomato Plants
The first step in addressing your frostbitten tomatoes is determining whether they can be salvaged.
The most prominent marker will be the fruit itself; if the tomatoes have frozen, they must be discarded. A frozen tomato plant may present with frozen dew balls on the fruit or frost between the stems.
Next, take a look at the leaves. The tomato plants are too damaged to be saved if they have:
- Extensive discoloration on the leaves between the veins,
- The plant sags to the ground, or
- The plant presents with soft stems or wilted leaves.
If discoloration is only on the outer leaf edges, the plants will likely survive. Discoloration may appear brown, tan, or black in color.
The stem is the lifeblood of the plant. If the main stem appears healthy, wait a few days and continue caring for the plants as normal. It may present with new growth and if this is the case, the plant should recover fine.
This short video shows great examples of identifying damaged plants versus ones that will recover after a frost.
The following table summarizes the effects of varying temperatures on your tomato plants.
|Temperature||Impact on Tomato Plant|
|Below 33 ̊F||Plant is unlikely to survive unless protected prior|
|33 – 50 ̊F||Plant may suffer damage, but may be able to be saved depending on length of the frost|
|50 – 60 ̊F||Tomatoes may not ripen properly|
|60 – 75 ̊F||Ideal temperature for tomato growth|
|75 – 89 ̊F||Fruit may not ripen, can cause blossoms to drop|
|Above 90 ̊F||Can cause poor crop, especially when combined with high humidity and draught|
Source: Missouri Botanical Garden
How to Save Your Tomatoes Affected By Frost
If the plants are presenting as mildly frosted and not completely frozen, you can try spraying the plants with water in the early morning before sunrise. This will melt the frost and may assist recovery.
Once the frost has subsided, you should prune the affected leaves off of mature plants with gardening shears coated in rubbing alcohol.
Another option is to pinch the stems of the leaves where the healthy plant tissue meets the frostbitten pieces. This will help prevent the further spread of disease and rot.
Saving young tomato plants as well as established plants depends on the protection from further frost.
While tomatoes may survive one frost, the more times the plant is exposed to improper temperatures the less likely it is to ripen properly. This is why it is important to be prepared in advance when faced with the potential of poor weather conditions impacting your garden.
Using a weather app or website which shows historical temperature data can be a great planning resource.
If you are trying to protect your tomato plants prior to the end-of-season:
- Harvest the mature, green fruits,
- Wrap them in paper or cardboard and
- Store in a cool location such as the garage.
This will prevent the crop from ripening. When you are ready to use them, bring the tomatoes out of storage and leave them in a warmer, dry area.
How to Protect Your Tomatoes from Frost
- Keep track of the weather in your area and future frost conditions
- Understand the ideal growing season for your region
- If using containers, move the plants to a safer area
- Cover new tomato plants with plastic containers
- Use tarps, sheets of fabric, or plastic to cover matured plants
- Grow tomatoes indoors using artificial light or a bright enough window
- Keep plants properly hydrated
- Use a thermometer at plant-level to keep track of temperatures
- Use hybrid, frost-resistant tomato plant strains
- Plant your tomatoes in an upside-down, hanging container which can easily be moved
- Use additional heat and light sources such as incandescent (non-LED) string lights to keep your plants warmer
- Spray an anti-transpirant product the night before a light frost
Be sure to remove any coverings the next morning so your tomato plants can warm up in the sun.
Additionally, when using plastic coverings ensure the plastic is not actually touching the leaves of the plant as this will cause the condensation to buildup and freeze the leaves. One way to avoid this is by using a planting cage or stick to create a ‘teepee’ type enclosure with the plastic.
These tips will help protect your tomatoes from lighter frosts which do not last long. Covering tomato plants will not protect them from hard frosts, or frosts where the soil and ground freezes.
These types of freezes usually occur when the planting season is coming to an end and signifies you need to harvest the remainder of your matured tomatoes.
Ideal Tomato Growing Conditions
For the most successful tomato crop, be sure to plant them after the last frost in your region. This is usually in the late spring or early summer months.
According to the United States Department of Agriculture, tomato plants thrive best in plant hardiness zones 10 and 11. This zone is comprised mostly of areas in the Southern United States and parts of California. But tomato plants can be planted anywhere in zones 4 to 9 as well, just by using some extra effort to protect them from the weather.
You can use this link to check your zip code’s plant hardiness zone to fully understand which plants will thrive in your region. Here are some additional tomato growing tips:
- When using a container, ensure it is large enough for your plant – 12 inches is usually sufficient for tomatoes
- Select the right varietal of tomato for your planting area and planned use
- Fertilize every week using compost or organic planting mix
- Use loose, well-drained soil and keep it damp
- Give at least eight continuous hours of sunlight to your plant, but preferably more
- Prune your tomato plant from the bottom to prevent fungus
- Do not plant your tomato plants too close together
- Test your soil pH – The Farmer’s Almanac recommends slightly acidic soil with a pH of 6.2 to 6.8
- If growing from seedlings, harden off the seeds before transplanting to an outdoor garden
- Be aware of various pests and plant diseases and how they present in tomato plants
The Bottom Line for Your Tomato Plants
While it is possible to grow tomatoes wherever you are, more effort may be required to keep your plants safe in regions that experience colder weather.
Using these tips and proper maintenance of your plants can help you avoid the negative effects of frost and cold temperatures, and result in delicious, garden-fresh tomatoes year-round.