Got milk? Use it in your garden. The beverage isn't just good for the human body, but it's beneficial for plants, too. Milk serves as a fertilizer for your garden to help plants grow, as well as has antifungal and pesticidal attributes.
Pros and Cons of Milk in Gardens
The same properties that make milk good for a human, such as the calcium and B vitamins, are what benefits plants. The calcium helps the plants grow, as well as prevent blossom end rot, which can be caused by a calcium deficiency. This condition is common in tomato, peppers, and squash plants.
Milk's antifungal properties are well researched within the scientific community, with successful outcomes in treating powdery mildew, a fungal condition impacts many economically important crops such as grapes.
However, milk isn't a panacea when it comes to growing plants. Using too much can result in a destroyed plant, thanks to the bacteria in the beverage that can stunt growth and cause wilt. The fat in whole milk can also cause a foul odor, while skim milk could lead to black rot, soft rot, and Alternaria leaf spot on certain crops.
How to Use Milk on Plants
Any type of milk, including fresh, expired, evaporated, and powdered, can be used in a garden as long as it's diluted properly. Stick with reduced-fat (2 percent) or low-fat (1 percent) milk, rather than skim or whole options.
Mix the milk with water in a 50-50 ratio and pour it into a spray bottle. Watering down the milk is essential to ensure it actually benefits your garden, rather than destroying the plants. The ratio doesn't have to be exact—in fact, you can even just mix up the very last dregs of the gallon as you finish off the jug, using just a quarter-cup or so of milk.
Apply the milk mixture to the leaves of the plants, checking back about 30 minutes to ensure that the watery milk was absorbed. If there's still liquid sitting on the leaves at that time, gently wipe them down with a wet cloth. Certain plants, such as tomatoes, are prone to developing fungal diseases if liquid sits on the leaves for too long. You can also pour the milk mixture directly into the soil at the base of the plant, which will allow the roots to absorb it.
If you have a large garden area that you want to spray with a milk solution, use a garden hose sprayer. Approximately 1 quart of milk will cover a 20- by 20-foot garden, while 5 gallons of milk should cover 1 acre.
After applying the milk, refrain from using a chemical pesticide or fertilizer on the plants, which will kill the bacteria in the milk that helps the plants grow. After using the milk on the plants, there might be a slight unpleasant odor; however, it will eventually subside.
Bettiol, Wagner. “Effectiveness of Cow’s Milk against Zucchini Squash Powdery Mildew (Sphaerotheca Fuliginea) in Greenhouse Conditions.” Crop Protection, vol. 18, no. 8, Sept. 1999, pp. 489–92.