Should I Pour Milk onto My Tomatoes?
Photo: C. Gibson
Probably not.
The dreaded blossom end rot - when you’ve spent time, money, and energy trying to grow the most delicious home garden tomato only to find that the bottom of the fruit is mushy and discolored or missing. There are plenty of suggested remedies for how to prevent future mushy fruits, from pouring milk on the soil, crushing up eggshells, burying crushed antacid tablets, to traditional fertilizing and more. What’s really going on with this problem?
To start, plants are living things that need water and energy to survive. In order to make energy, plants transport nutrients from the environment into their bodies. Many plants use roots to move nutrients from soil using water and differences in pressure and concentrations. One of those nutrients in calcium, which plays an important role in building structures in plant bodies, similar to how it functions in animal bodies.
Photo: C. Gibson
When calcium does not (or cannot) move through plants all the way into fruits like tomatoes, peppers, eggplants, and squashes, the mushy signs of blossom end rot start to show. It is much less common that soils or potting mix is lacking the amount of calcium these plants needs. Since bodies need fluids to move nutrients around, blossom end rot is usually caused by not enough or inconsistent water, trapping the calcium in the soil or in lower parts of the plant out-of-reach of the fruits.
Adding more calcium in traditional or creative ways does not address the underlying problem of blossom end rot. As an astute musical poet once said, “It’s like ten thousand spoons when all you need is a knife” - all the calcium in the Earth won’t help a plant that can’t transport it to its destination. So what does help? Try not to let your soil stay dry for too long. And as you can imagine, this is more of a problem for container gardeners.
Some plants can grow roots in less common places when experiencing water stress, like this Lucid tomato’s adventitious roots. Photo: C. Gibson
If you’re not sure why calcium isn’t making it to your fruits, look for signs of low or inconsistent watering, such as crispy curly leaves, containers that seem dry and not heavy enough, or thick H. R. Giger-inspired growths that start bursting from the stem (“adventitious roots”). In addition, mail-in soil tests are affordable, simple to dig, and results often come with suggestions for your specific nutrient profile. A quick Internet search or call to your local Extension office can provide instructions, or reach out to a garden partner at Leaf & Bed to walk you through it.
So, should you buy an extra bottle of antacid to bury with your seedlings? It probably won’t hurt, but it will be more effective to add a water tray under your containers, install an affordable drip water line, or pay the friendly neighborhood plant sitter to water a little more frequently during dry spells.
Sources consulted:
Cornell University College of Agriculture and Life Sciences, Plant Disesase Diagnostic Clinic. Updated 2018. “Blossom End Rot.” Accessed August 2023. blossomendrot.pdf (cornell.edu)
Joy, Ann and Brian Hudelson. University of Wisconsin-Madison Plant Pathology. Revised April 1, 2005. “Blossom End Rot.” Accessed August 2023. Blossom End Rot – Wisconsin Horticulture
Salzer, Troy. University of Minnesota Extension. February 3, 2021. “Blossom End Rot in Tomatoes and other Vegetable Crops.” Accessed August 2023. Blossom End Rot in Tomatoes and other Vegetable Crops | UMN Extension
University of Maryland Extension. Updated February 20, 2023. “Blossom End Rot on Vegetables.” Accessed August 2023. Blossom End Rot on Vegetables | University of Maryland Extension (umd.edu)
Updated 9/9/2023 CG