Updated: Sep 29, 2020
It is true, you can make a organic home-made fertilizer tea from the weeds you pick out of your garden. Although there is little scientific evidence around this, many gardeners regularly use this technique to feed their plants and make use of their weeds at no cost to them with positive results. In addition to nutrients, weed tea can also benefit plants and soil by the microorganisms it contains, which assist in breaking down organic materials in the soil into plant food. Some chose to spray this tea onto the leaves of plants with the idea that it makes them stronger and more resistant to disease or pests. To make weed tea, weeds are placed in a 5 gallon bucket and covered in rain water. In anywhere from 3 days to 3 weeks the water is separated from the weeds and used to fertilize plants.
The main nutrients in plant fertilizer you purchase include nitrogen, phosphorus and potassium (or potash). Nitrogen encourages leaf growth, phosphorus promotes root growth and potassium is great for encouraging your plants to blossom and to produce fruit. Other nutrients required by plants include calcium, sulfer, zinc, manganese, boron and iron.
When choosing weeds for your fertilizer tea be sure to select weeds that have not yet begun going to seed. You don't want to be planting more weeds in your garden through this process! For organic fertilizer ensure the weeds have not been sprayed with chemicals.
Below are some common zone 3 weeds that make a nutritious base for your fertilizer tea.
Alfalfa is high in nitrogen, potassium and calcium as well as vitamin A, folic acid and trace minerals.
Chickweed is rich in phosphorus, potassium and manganese. This weed is identified by its vining, low to the ground growth and its small rounded leaves.
Comfrey is recognised by its large, broade leaves and small purple flowers. Comfrey contains phosphorus, potassium, calcium and magnesium as well as vitamins A, B & C and trace minerals.
Dandelions are likely something nearly everyone has access to and are rich in potassium, calcium and vitamins A & C.
Stinging Nettle is something you likely never hoped to find in your garden but it makes the perfect base for fertilizer tea containing high levels of nitrogen, phosphorus, potassium, calcium, iron, boron, zinc and magnesium as well as vitamins A, B, C and selenium. As it's name suggests, this plant will cause pain if it comes in contact with your skin. It is best to wear gloves and long sleeves when harvesting this. Nettles grow tall and are recognised by their hairy leaves with distinct jagged edges.
The specific weeds listed here are not necessary for your fertilizer tea but make a great addition if you have them available to you. Next time you are weeding your garden throw the weeds into a pail and top with water. Really this is all it takes to make a simple fertilizer tea for your plants.
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Weeds are not the only thing that can be used to feed your plants. Other options to consider adding to your fertilizer tea include compost, fresh grass clippings (high in nitrogen and potassium) banana peal (potassium), dried eggshells (calcium) and unsalted water leftover from your cooking.
Once you have gathered your weeds put them into a 5 gallon pail. They can be chopped up for better nutrient absorption. If possible, cover the bucket with a breathable cloth to keep insects out. The fertilizer tea can be used after steeping anywhere from 3 days to 3 weeks. You will notice it will begin to smell strongly like cow manure and the water will turn black and stain (so be careful when using). This is not a bad thing but means that the microorganisms are multiplying. If you are using it after 3 days it does not need to be diluted. If you have left it a week to 3 weeks, dilute approximately 1 part tea to 9 parts water. If you have a screen the weeds can be strained out and the tea water used. If not, just dip a container into the bucket to use the tea. This fertilizer can be used on your plants as often as once a week.