Eggshell Vinegarite for Treating Blossom End Rot in Tomatoes

Raise your hand if you have ever put an eggshell in the hole when planting tomatoes to provide an extra calcium boost for your plants.  Or if you know of someone who does this.  Or if you just toss them in the compost pile.

I can say yes to all three.

But apparently all those practices are just an exercise in futility, if the aim was to get calcium into tomato plants, ostensibly to prevent blossom end rot. 

Studies over the last couple of decades have demonstrated that the calcium in eggshells is completely unavailable to tomato plant roots unless it is finely powdered.  They say it takes a really long time for eggshells to decompose.  We can’t just throw eggshells in the planting hole or scatter them about willy nilly.  And that is because crushed eggshells contain an insoluble form of calcium which is unavailable to plants unless it is very finely ground, like occurs with ground limestone or bone meal purchased from nurseries for use in the garden.[i]

(And yes, I was a little suspicious of the claim—after all, I’ve never found any eggshells when digging up the garden in subsequent seasons.  But maybe that’s because they were dirty, being in dirt and all that, so that I couldn’t identify them.  And then someone pointed out that eggshells do not dissolve in water, ever.  Duh.)

The reason for putting eggshells in the planting hole is to give tomato plants an extra shot of calcium to prevent blossom end rot.  Unfortunately, it just doesn’t work that way.  However, if you’ve ever had a plant producing tomatoes with blossom end rot, you know you want to take care of it right away.  You don’t want to risk losing the entire harvest from that plant.  Right now, it’s just a frustrating annoyance.  In the future, such a loss could be devastating.

So what do you do?

Make an eggshell vinegarite. 

Just like with people, medicine has to get to the tissue in plants to work as well.  In this case, calcium is the medicine tomato plants need to prevent blossom end rot.  And to keep from losing the entire harvest, it needs to get into the plant tissues as quickly as possible.  Vinegar extracts the calcium from the eggshells rapidly.  The solution is then filtered and diluted and put in a spray bottle to apply the solution directly to the tomato leaves.

Here’s how:

Eggshell Vinegarite (from the College of Tropical Agriculture and Human Resources at the University of Hawaii, a pdf I accessed just days ago but is now unavailable)

•          Remove internal membrane from shells.
• Crush eggshells.
• Roast shells in frying pan over low heat for 45 minutes to remove organic substances.  They should be dry and lightly tanned, not charred.
• Add eggshells in a 1:10 weight to volume ratio to a jar of vinegar.  Eggshell fragments will rise and fall in the vinegar, emitting carbon dioxide bubbles as the vinegar dissolves the calcium from the shells.
• Place a coffee filter or lightweight fabric over the jar opening and secure in place with a rubber band to keep pests out.  Set in a cool, dark location for 7-10 days.
• If there are still bubbles present, add more eggshells and repeat above process, letting the mixture sit for another 1-2 days.  If there are no bubbles, the process is complete.
• Strain the solution into a clean glass jar.  Label the solution and store at room temperature away from direct sunlight.[ii]

As the above comes from a university agricultural department, it ought to be good.  However, it strikes me as unnecessarily complex.  Removing the inner membrane from each eggshell?  I don’t think so!

The following method is recommended by Calvin the Tomato Geek.

•          Rinse and dry eggshells.
• Bake at 200°F for 30 minutes or until completely dry.
• Pulverize eggshells in coffee grinder, food processor, or blender.
• Use a 1:1 ratio to make the vinegarite, i.e., 1 tablespoon ground eggshells to 1 tablespoon vinegar.
• Let sit 1-2 hours, up to 1 week.
• Strain to remove the eggshells and store solution in a clean jar.
• To feed tomato and pepper plants, add 1-2 teaspoons vinegarite per gallon of water and spray leaves liberally.[iii]

So is this eggshell vinegarite something you need to make for your tomatoes?  Well, if you’re suffering from blossom end rot, this may save your bacon.  Keep in mind that most soils are not calcium-deficient because gardeners often apply calcium to the soil in the form of ground limestone or gypsum before beginning work in the garden each season.[iv] 

This eggshell vinegarite offers a water-soluble form of calcium as an alternative to commercial products that may not be available in the future, particularly when survival may depend on a good harvest.  Not only is it critical to prevent blossom end rot in tomatoes so that current year’s harvest isn’t negatively impacted, but also for future harvests.  Seeds that are deficient in calcium (such as those saved from a tomato with blossom end rot will be) generally have poor germination rates and produce abnormal, weak seedlings.[v]

Researchers noted that most soils are not actually deficient in calcium.  However, excessive amounts of sodium, potassium, or magnesium in the soil will interfere with calcium availability.[vi]  In addition, calcium may react with other soil nutrients to form insoluble compounds that can’t be used by plants.[vii]  And finally, because this vinegarite can be washed off easily, don’t apply it right before a rain storm.

Links to related posts:

Starting Tomatoes from Seed  

DIY Complete Organic Fertilizer  

References:

https://www.ctahr.hawaii.edu/oc/freepubs/pdf/SA-10.pdf

https://tomatogeek.com/eggshells-for-tomato-plants/

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[i] https://studylib.net/doc/18788047/crushed-eggshells-in-the-soil---alabama-cooperative-exten

[ii] https://www.ctahr.hawaii.edu/oc/freepubs/pdf/SA-10.pdf

[iii] https://tomatogeek.com/eggshells-for-tomato-plants/

[iv] https://www.ctahr.hawaii.edu/oc/freepubs/pdf/SA-10.pdf

[v] https://www.ctahr.hawaii.edu/oc/freepubs/pdf/SA-10.pdf

[vi] https://www.ctahr.hawaii.edu/oc/freepubs/pdf/SA-10.pdf

[vii] https://www.ctahr.hawaii.edu/oc/freepubs/pdf/SA-10.pdf