I always recommend waiting until all chances of frost are gone before planting tomatoes here in North Texas. Tomatoes are extremely frost sensitive. Even if frost doesn’t kill them, it can severely damage foliage. Planting early is very risky.
Yet, some plant tomato seedlings as early as the third week of February in North Texas in order to give them a headstart. Is planting tomatoes early a smart strategy or risky mistake?
Comparing planting times
This year, I plan to conduct an experiment by planting a few tomato plants during the third week of February and protecting if frost threatens, and then planting the rest after last frost when there is no longer threat of frost.
Experience tells me that planting before last frost doesn’t actually give the plants any kind of advantage because they are growing in such cold temperatures and soil, and there is a strong likelihood that a freeze will cause severe damage even if plants are covered. I also believe that waiting to plant them later gives them more time to grow in protected conditions, thus giving them an advantage over earlier planted seedlings.
What the research says
Research shows that the age of a tomato plant at transplant matters.
A 2013 study found that seedlings with 7-8 leaves at transplanting produced 26% more fruit than tomato seedlings transplanted at 5-6 leaves, and that tomatoes started producing earlier when transplanted with at least 7 leaves.
This same study also found that older transplants started to flower and fruit faster than younger transplants. Tomatoes transplanted with 9-10 leaves flowered 8-12 days earlier than those with 5-6 leaves and 3-4 days earlier than transplants with 7-8 leaves.
Researchers concluded that transplanting a tomato seedling earlier had no positive effect on tomato fruit yield, earliness, or fruit size.
What about temperature?
Not only are tomato transplants younger/smaller when planted before the last frost, but they are planted when temperatures are still very cold.
A study published in the Journal of Plant and Soil found that tomato seedlings planted when air and soil temperatures were below 50 degrees had low concentrations of nitrogen, potassium and magnesium among other nutrients, while later plantings had adequate nutrition. When soil is cold, tomatoes can’t properly take up nutrients as they grow. As a result, nutrient levels in the plant become very low.
What you should do
Because my number one priority is your success, I would never encourage you to plant tomatoes before mid-March unless you have a good number of years growing tomatoes under your belt, or you are willing to risk the death of your tomato seedlings.
Action steps
- Start tomato seedlings indoors between January 15 and January 31, or purchase transplants when available in nurseries.
- Once indoor-started tomato seedlings outgrow the cell tray, pot them up into 2.5″ to 3″ nursery pots and harden off by gradually exposing them to outdoor conditions.
- For both indoor-started and purchased transplants, keep them in their pots until mid-March or until there are no more chances for a freeze in the forecast. Move potted seedlings indoors whenever freezing temperatures occur.
- Transplant out into the garden – ideally the seedlings will have at least 7 or more leaves at this point – and keep frost cloth handy in case of a late freeze.
Test results
I will update this post at the end of the spring growing season to let you know how the early-planted tomatoes fared compared to later-planted tomatoes.
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References
Gent, M.P.N. Effect of planting date, ventilation and soil temperature on growth and nutrition of tomato in high tunnels. Plant Soil 145, 81–91 (1992). https://doi.org/10.1007/BF00009544
Javanmardi, J., Rahemi, M., & Nasirzadeh, M. (2013). Physiological and Reproductive Responses of Tomato and Pepper Transplants to Low-Temperature Conditioning. International Journal of Vegetable Science, 19(3), 294–310. https://doi.org/10.1080/19315260.2012.726956
J., Jankauskienė & Brazaitytė, Aušra & Bobinas, Ceslovas & Duchovskis, Pavelas. (2013). Effect of transplant growth stage on tomato productivity. Acta scientiarum Polonorum. Hortorum cultus = Ogrodnictwo. 12. 143-152.
Dufault RJ. 1998. Vegetable transplant nutrition. HortTechnology. 8:515–523. https://doi.org/10.21273/HORTTECH.8.4.515.
Maynard, E. T., Guan, W., Langenhoven, P., & Hoagland, L. (2024). Tomato Seedling Performance in Commercial Organic Growing Media. HortTechnology, 34(1), 80-91. Retrieved Jan 30, 2025, from https://doi.org/10.21273/HORTTECH05244-23
- Early Tomato Planting: Smart Strategy or Risky Mistake? - January 29, 2025
- Starting Seeds Indoors: Common Problems - January 25, 2025
- Freeze-Damaged Plants: What to Do Now? - January 10, 2025
