Milk and Tomato Growing

You may have heard or read that milk is sometimes used to help grow tomatoes–and also squash.

Is it a fertilizer?

Milk contains calcium (Ca). Calcium is an important plant macronutrient. Macronutrients are foods that help plants grow and function. Calcium helps build plant cell walls which in turn allow the transport of other plant nutrients. Also calcium level in the soil controls the soil pH (pH is a chemical balance that allows plants to operate, or not). If calcium is washed out of the soil, the soil will become more acid and can affect plant growth. (Agricultural lime such as dolomite lime contains calcium.)

If you feed plants milk–whole milk or powdered milk–you are feeding plants calcium.

So milk can be a tomato plant fertilizer: Sprinkle a quarter to a half cup of powdered milk on top of the soil after planting, and repeat every two weeks throughout the growing season.

What else does milk do for plants?

Milk is a fungicide.

Old-time garden wisdom AND recent scientific plant research say that milk contains fungicidal properties. If you spray milk on plants, it will control the growth of bad fungi.

Fungi are microscopic organisms. A handful of soil contains thousands and thousands and thousands of fungi. There are good fungi and bad fungi. Good fungi help build the soil by breaking down organic matter into nutrients plants can use. Bad fungi are parasites that feed on plants. Bad fungi include mildews (downy mildew, powdery mildew), rusts, rots (root rot, damping off, fruit rot), canker, scab, spot (black spot and anthracnose), wilts (fusarium and verticillium) and smuts (and black sooty molds caused by black sooty fungi spores).

Fungi are spread by spores. They germinate and root much like plants. When a fungi takes root as a parasite on plant tissue it feeds and begins to grow. A fungus can be prevented from rooting and can be removed (prune off the infected plant tissue and throw it away in a paper bag so that the fungi spores do not spread). Fungi allowed to grow will spread via spores floating on the wind or swept along in a drop of water.

Fungicides rarely kill fungi. They are most useful as a preventive, not as a cure. Fungicides cover plant tissue and do not allow fungi to root.

Plant researches in Brazil and Australia have recently used milk as a fungicide on vegetable crops, grapes, and flower crops. They found that spraying a dilute mix of 1 part milk and 9 parts water prevented fungi from growing. (The researchers also believe that the potassium phosphate in milk helps boost the plant’s immune system and may also work as an antibiotic.)

Once again, milk–like other fungicides–does not cure fungal diseases but helps to prevent them. Milk keeps fungi from growing and spreading.

A note: skim-fat milk works best; the fat in whole milk may clog up your sprayer. As well, reconstituted powdered milk will work.

Tomato disease fighter formula: combine 1 part skim milk and 9 parts water. Spray the plant every two to three weeks until mid-summer (most fungal diseases have run their course by mid-summer, except where the weather stays warm and humid).


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  1. Thank you very much. We are doing an experiment about what is the effect of types of liquid on plant’s growth. I was asssigned to research facts about milk and what in it will possibly affect growth of the plant, height growth particularly. Thanks. I’m a 6th grader student of Salk School.

    • Your very welcome. It’s great to hear from a sixth-grader doing plant research. The calcium in milk not only helps build plant cell walls, it also helps build strong bones in sixth graders. Thank you Tina and Harry for writing. I am sure your research will turn up very interesting information on plant growth.

        • Some non-natural, manufactured additives may stunt or harm plants. You can do a simple test, by using the protein powder on a few plants and compare the growing results to the plants you not treat with the powder. Keep a simple day-to-day log of your observations.

    • Hi Tina, this is super cool, question how did your experiment go?, my sister was given a couple champion pumpkin seeds for my nephew who has autism and they want to grow a really big one! Have any tips or suggestions for them, any help is appreciated. Good luck on future studies.

    • In these instructions if 1 part were 1 cup then 9 parts would be 9 cups. If 1 part was 1 gallon then 9 parts would be 9 gallons. You can determine what amount is 1 part.

    • Yes, milk is a good source of calcium for plants (and humans). It contains beneficial proteins, vitamin B, and sugars that can improve overall plant health and yield. Milk can replace the lack of calcium that causes blossom end rot in squash, tomatoes, and peppers. Do not use milk as a fertilizer at full strength–dilute the milk by 50 percent with water.

  2. I have just read your article on adding milk to tomato plants. It contained a common misconception. My understanding is that it is the carbonate in the lime or dolomite that neutralizes soil acidity, not the calcium content. Therefor other compounds containing calcium may or may not alter the pH depending on what else is in the compound. For example gypsum contains lots of calcium but does not change the pH. Of coarse the addition of calcium will have other benefits if there is a calcium deficiency in the soil.

  3. There is one side effect when you add 3 Tablespoons of Blackstrap Molasses per gallon of the milk mixture! It turns out as a lot of insects have Diabetes and can not digest sugar two of these bugs are grasshoppers & Aphids and it gives them stomach aches In other words it acts as a natural insecticide and the nice thing is it is selective and will not bother any beneficial insects!

  4. What is the ratio of powdered milk to
    water? Also, if you have any other suggestions, I would greatly appreciate it!! My tomatoes have blossom end rot.
    Thank you in advance!

  5. How often do I use the powered milk water treatment. I was told I could crush up one antacid to one gallon water stir well and water 2 cups per 5 gallon. Container tomatoes. I watered them with that once. Either with that mixture or powdered milk to water mixture how often would I water my container tomatoes( that already have blossom end rot) with the milk mixture.

    • One dose of powdered milk should be sufficient. Blossom end rot is temperature related. As the soil temperature warms, plants will be able to draw up calcium from the soil. Chilly soil temperatures lock-up calcium in the soil; when the soil warms the chemical process to draw up calcium is initiated.

  6. Also my powdered milk i happened to have on hand says on he label.. cholesterol 4 mg, sodium 126 mg, Sugar’s 12 G protein 8G vitamin A 11% vitamin C 2% calcium 28% and vitamin D 25% so my question is is this powdered milk even has have enough calcium in it along with other things would it be safe to use

  7. I have one tomato plant in container. Larger tomatoes have blossom end rot. With the milk, do I put it in soil with water or spray on leaves and tomatoes?

    • You can remove the fruit with blossom end rot; it is not uncommon for early developing fruit to develop blossom end rot. And you can spray the plant with a milk spray and feed it with a fertilizer that has magnesium and calcium added such as Lily Miller Mor-Crop. The fruit that follows should be fine; be sure to keep the soil just moist–not too wet, never dry.

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