Using Yeast in the Garden

Yeast have accompanied humans for millennia and were initially used to make nourishing drinks, as they are packed with vitamins B, C and D, peptides, amino acids and microelements such as silica, trivalent chromium, phosphorus, selenium, and iron. Culinary yeast, Saccharomyces cerevisiae, belongs to the Kingdom of Fungi, along with mushrooms and molds. Often present on the peel of fruit, it shows as a whitish layer on dark grapes or dark plums.  

In our culture, yeast is mostly known to bread and doughnut makers, beer and wine makers, and those who produce hard alcohol. Yeasts facilitate fermentation which converts carbohydrates into alcohols and carbon dioxide — seen in consumable alcohol production as bubbles or in baking seen as tiny holes in expanded dough.  

There are several strands of yeast: some better suited for baking, others better for fermentation of alcohols. Yeast can also serve as medicine and as an ingredient for natural cosmetics. 

This nutritious fungi we’ve drunk for millennia can also be of use in our garden as fertilizer either fermented or unfermented. Besides gaining nutrients, plants benefit from yeast cells colonizing the roots which offers protection from harmful organisms.  

Yeast-based Fertilizer 

There are several ways to prepare a yeast-based fertilizer. Some call for the addition of flour or old bread to the yeast during the fermentation. Others recommend adding ash and topping the soil with broken eggshells to replace calcium and potassium in the fertilized soil.  

A fermented fertilizer is prepared in a vessel with about 3 gallons capacity. Begin with 1 oz of dry yeast and 1 cup of sugar mixed, then add ½ to ¾ cup of warm water. After one or two hours, dilute the mixture with 2 ½  gallons of warm water.  

The water used need not to be from the tap. It can be rainwater, or water used previously for boiling or steaming vegetables — another great way to recycle 

The yeast, sugar and water mix should sit at room temperature for a week to ferment. The mixture should then be diluted to 1 cup of mix to 2 ½  gallons of water. 

Unfermented fertilizer is simpler to make. Mix 1 oz of dry yeasts with 2 ½  gallons of lukewarm water. After one hour the product is ready to use. 

When to Use Yeast Fertilizers 

The yeast-based fertilizer can be used for the whole gardens and for houseplants, although is particularly suited for tomatoes, cucumbers and strawberries. It promotes rooting, so the first application should happen when the plants are still small seedlings. The application should be repeated when plants flower. The third application should occur when fruit appears. It is not recommended to use the mix more than three times during the growth season. 

Yeast-based Crop Protection Spray 

Rather than using insecticides, herbicides, or fungicides, yeast can be used to protect your garden in a safer manner. 

Dissolve 1 oz of dry yeast in 2 cups of lukewarm, whole, preferably unpasteurized milk. The mixture is then dissolved in 2 ½  gallons of lukewarm water.  

To make the spray stick to the surface, an addition of a tablespoon of natural potassium soap comes in handy, or some add a couple of drops of dish detergent. The mixture can be sprayed or simply poured on the plant top down and also on the underneath side of the leaves. 

The spray can be applied weekly to protect against late blight caused by common water mold like Phytophthora infestans, and fungal infestation by Erysiphales sp. which cause a white layer on the leaves and botrytis. Tomatoes, cucumbers, strawberries, and roses will benefit from this spray the most. Yeast on the plant surface tend to outcompete the other organisms. They are also known not to produce any harmful metabolites and thus will not harm one’s bacterial intestinal flora upon eating treated foods. 

By Joanna Rosińska 

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