Planting Tomatoes When the Soil is Too Cold

When planting seeds or transplants it is important for the backyard grower, community gardener or urban farmer to keep track of soil temperatures, as the soil is where the seed will germinate and where the roots are located.  It is not uncommon to have a large difference in soil temperature in relation to air temperature, especially early in the season.  A grower can get fooled into thinking the time is right for planting based on a warm sunny spring day when the soil temperatures are not actually at the point ready to plant.  I see tomatoes planted each year in April or early May that have been planted too early.

When planted before the soil warms up, phosphorus is not able to be taken up by the plant, even if enough phosphorus is present in the soil.  This manifests in a purple discoloration of the tomato leaves, especially the older leaves near the bottom of the plant.


The purple coloration is from anthocyanin, the same pigment that gives blueberries its color.  Phosphorus is a critical macro-nutrient that assists seedling growth and vigor.  These tomato plants are at risk of further disease or insect damage due to being stressed from nutrient deficiency.

To remedy this, you need to deliver phosphorus to the plant.  The best way would be to use a foliar feeding of a water soluble fertilizer containing phosphorus applied to the leaves, top and bottom.  This should be done early in the morning before the tomatoes stomata close. (the pores on the leaves).  Once the soil warms up the tomato will start to take up phosphorus if enough nutrient is present.  You may need to foliar feed until this occurs.

It is important for the backyard grower, community gardener and urban farmer to monitor soil temperatures to ensure that seeds and transplants go into the ground at the correct time to maximize production success and minimize potential problems.

Ohio State maintains a website with soil temperatures at all of the OARDC stations.  Click here for the link to check soil temperature in your part of Ohio.


6 thoughts on “Planting Tomatoes When the Soil is Too Cold

        • Terry, I am unsure if that would work. Water is a very rapid and efficient thermal conductor. It could rapidly warm then provide a conduit to cool. I would recommend that you put either clear or black plastic over the site a few weeks prior to planting to warm the soil a few inches deeper.

  1. Planting your tomatoes in the middle of a swath of porous black landscape cloth will more fully capture the rays of the sun to heat the soil. In addition, it will also make it unnecessary to hoe away unwanted grass and weeds. If you use an auger bit to create the plant holes just, auger a row of holes each one 2 to 3 ft. apart, clear the dug soil into a yard wagon or container, roll the landscape cloth over the holes, by feel of the edges of each hole cut X opening into the opening and fold back place your plants into the holes and backfill the extracted dirty, smooth out and tamp down the soil and pin the X flaps back into flat place, and mulch 18” out and around each plant. You will also well serve indeterminate plants if you keep elevating the growing vine ever higher onto an overhead trellis system of your own simple design. Also, if you are as silly as I am about enjoying growing tomatoes you may want to go out and talk to them several times a day—and also nip off the sucker shoots that grow between leaf shoots and the plant’s stem

    • By the way, I tack down all of the edges of the landscap cloth with platic pegs that are usually sold somewther near the cloth.

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