[Time to read: 6 minutes]
July 1, 2025
I have told many of our clients about my use of Biodynamic Fermented Weed Tea. Using this tea has convinced me that biodynamic farming is a game changer and can help create a healthy vineyard without the use of harmful chemicals.
I got started in biodynamic farming at Panther Ridge early in 2019, after working with a wonderful French consultant from Burgundy, Pierre Milleman. Pierre worked with me for a couple of years, introducing the basic biodynamic compounds to me and how and when to apply them.
There is a lot of information on the web about biodynamic farming in print and on the web, so I won’t go into that in depth here, except to say that it involves working with the natural rhythms of the earth and the cosmos to support traditional farming methods.
Sometimes it is hard to see the immediate results from the basic remedies. They support the microbiome of the vineyard and promote diversity. When you dig a hole in the ground at Panther Ridge (if you can dig one – it is very difficult because of so many rocks!) you find a multitude of earthworms thriving. You won’t find that in a vineyard that sprays pesticides and herbicides.
But one area of biodynamics that has shown clear results for me is a recipe I found for Fermented Weed Tea. I found a brief reference to this idea in Pierre Masson’s book on biodynamic farming, but it was just one vague paragraph on page 151.
After further digging around, I found more specifics. It involves picking the weed or weeds you wish to eradicate, and you make a fermented tea from them to discourage their growth. It involves several steps that I will describe here.
First – I’ll show you the problem we had. When we planted our vineyard from a field of hay and thistle in 2016, our first obvious growth was a giant milk thistle plant around every vine. It was terrifying. We had to manually dig out each thistle plant from the vines. And the next year, we did more digging and weed whacking to control the thistle.
My vineyard management company tried to encourage me to use RoundUp to control the weeds and reduce the cost of eradicating them, but I just couldn’t do it. I was committed to farming organically, but there was no organic product that could control these weeds.
Then I discovered a recipe for biodynamic fermented weed tea. I wish I could tell you exactly where I found it – it remains a mystery.
This tea will not kill the weeds, but it makes the environment for their growth less inviting. You are basically sending a message to the weeds that they are not welcome here, and that their job is done. They won’t thrive in the soil after it is sprayed with this tea, which in turn nourishes the vines and other advantageous plants in the vineyard.
To make the tea, you take whatever weed you want to discourage, and you put it into a big garbage can and cover it with water and a securely fitting lid.
Every day you check it and stir it, and after a few days it starts to bubble and ferment. The weeds start to break down and the mixture creates a foam on the surface.
After about 2 weeks the fermentation stops, and you are left with a dark stinky mess of liquid. You dig out the soggy weeds (they are no longer viable and can go to the compost pile) and strain out the leftover and dilute the liquid to 1 part stink and 10 parts water into your sprayer. Then you spray that mixture over the soil in the early morning or late afternoon “when the moon is in cancer.”
WHAAAAT? What did I just say??? Well, there are a number of biodynamic calendars published each year, and one of the most popular is based on the research of Maria Thun (pronounced “toon”).
Inside the annual publication are explanations of biodynamic remedies as well as specific calendar dates and when are the recommended times for tending to various types of plants, and which days are best for basically kicking up your feet and reading a good book.
The moon finds itself in cancer for 2-3 days each month. I figure, hey, I am going through all this work to make the tea, and I will spray it on a day or two when it is finished, so I may as well spray it when they recommend, okay? I don’t have to tell anybody about it — but I’m confessing this fact to you, dear reader.
So, I strain the mixture into my boom sprayer for my vineyard and add water to make the 1:10 ratio. You could dilute as much as 1:20 if you have a larger area to spray. As with other biodynamic preparations, you are using a dilute mixture. You are merely introducing the idea into the landscape, not spraying a concentrated product as you would in conventional or organic farming that directly impacts the soil or plants..
I spray the mixture onto the vineyard in the late afternoon on every other row with my boom sprayer. It takes me two days to do this given the limitations of my battery on my little golf cart and my patience for spraying – it takes about 2-3 hours each day to spray my 7-acre vineyard. If you have a smaller area to spray, you could spray the entire area twice in two days. If you have a larger area, you may need to keep the tea on hand and spray again the next month.
I have used this tea every year since 2020, and I have been able to steadily reduce the noxious weeds in the vineyard. After my first treatment for milk thistle in 2020, the next year the weeds were reduced by 2/3, and after spraying again in 2021 they were reduced even further. Now I have only a handful of milk thistle in the vineyard, and they are sickly and easy to remove.
I tried the same recipe with star thistle along my roadside where I had a terrible infestation. It has steadily declined to where I can now just pull the occasional star thistle plant as I walk the dogs in the morning.
This year I am making a mixed bag of all the noxious weeds I have seen and plan to spray on July 24-25 when the moon is next in cancer. This will be my basic maintenance plan now that most of the noxious weeds are under control.
I enjoy the messy vitality of our vineyard and much prefer it to the bare ground under the vines in many vineyards where herbicides are sprayed and the ground is dead underneath.
Here is a summary of the recipe:
Fermented Weed Tea – Biodynamic Recipe
- Pick the noxious weed of your choice – one variety or several
- Fill clean garbage can (or 5 gallon bucket) with the weeds and cover with water
- Cover and let sit for about 2 weeks, stirring almost every day
- The mixture will bubble up and start to ferment naturally
- After about two weeks, the fermentation slows down and you have a stinky mess
- Strain the liquid and put into a sprayer, about 1 part stink to 10 parts water (you can use more water if you need to spread a larger area)
- Spray with a boom sprayer or hand sprayer where you want to prevent weeds from growing
- Spray when the Moon is in Cancer (see Maria Thun or other biodynamic calendar)
This mixture will not kill the weeds, but it will make the environment less attractive to them. Spray every year for best results.
I wish you the charming messy vitality of life!