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Go Wild in the Country – Brewing beer with historic redwood yeasts


After attending a talk at NHC 2015 by James Howat of the http://www.blackprojectbeer.com/ on Spontaneous fermentation several members were enthused about trying some spontaneous fermentation ourselves.  A few months later  we got our chance at the clubs annual  camp trip at the historic Mount Madonna campsite near Gilroy

Mt Madonna is a county park of approximately 4000 acres near Gilroy, CA. . The park  is located amongst the Santa Cruz redwoods,  originally a summer retreat of Henry Miller who made his fortune in beef farming.

Redwood Trees

Redwood forests are a truly ancient phenomena,  trees such as the coastal redwood and famous Giant sequoia are some of the largest organisms in the world. The redwoods obtain a third of the water they require from coastal fogs, it can literally “rain” under the trees in summer.

This daily fog provides an excellent environment for microscopic organisms to live on the trees and for us wild yeast hunters an easy way  to collect yeast and bacteria due to the changing airflow. Sadly this coastal fog is threatened by climate change and is something we have noticed first hand, groups such as www.savetheredwoods.org are trying to study and prevent further tree loss.

Spontaneous Fermentation

WARNING: First a disclaimer as told to us by James. We are starting the fermentation process outside in a forest, so there is a risk of contamination from Clostridium botulinum, and its toxin, Botulism. We use phosphoric acid and a pH meter to make sure the wort pH is well below 4.6

The recipe and equipment

We decided to keep things simple with a basic lambic recipe for 10 Gallons

15lbs Pilsner Malt (Belgium)
10lbs White Wheat
1lb Rice Hulls ( to prevent the mash sticking)
2oz Tettnang (as old as you can get) 60minsEquipment:

  • Boil Kettle
  • Propane burner and tank
  • pH meter
  • Phosphoric acid (about 8oz 10%)
  • 10 gallon round igloo cooler
  • Thermometer
  • 1 packet cheese cloth to cover top of cooler and duct tape
  • Gallon carboys to split wort afterwards
Mash in

The first year we tried this recipe we milled the grains onsite, milling 25lbs with a grain mill takes a long time, so pre-crush is preferred We heated 9 gallons of Mt Madonna well water to 159deg and added it to the cooler for 60mins, drained then finished the batch sparge with an additional 6 gallons, giving us about 12 gallons of wort.


A normal 60min boil with the aged hops. At the end of the boil we added some additional cool water to help drop the temperature , and reduce the risk of DMS before putting back in the cooler.  We aerated the wort by splashing it into the cooler.


One thing that had always thrown a wrench into brewing in the woods was the lack of water for cooling, in California we have also had a drought so wasting water wasn’t an option. For spontaneous fermentation we want the wort to cool slowly.

Yeast harvesting

We taped the cheese cloth tight around the top of the cooler with duct tape. This is to stop insects falling in and prevent any critters dipping their paws in. We then placed the cooler next to  a redwood tree fairy ring where it would benefit from old and new growth trees overnight. We also tied the cooler to a tree as best as we could  to prevent tipping.

Draining the wort

The following morning each member tapped off a gallon or so of wort to take home. There were some brownish cell like material at the bottom but otherwise it looked like a normal wort.


Now the waiting part, unlike a tube of commercial yeast the wild yeast will take time to multiple into sufficient quantities, this can take up to a few weeks,  you will probably notice the water in the airlock rising first.  Once the yeast and bacteria take hold it can then continue to ferment for many months. If you see anything other than yeast you can skim them off or decant to a new container. Feel free to add fruit or other spices as desired. Make sure fermentation has completed before attempting any bottling

End result

During fermentation all sorts of strange aromas were given off, some rubber, some wheaty, some not beer like at all. However the first time we tasted the beer after it dropped  we were shocked,  it tasted like a perfect wheat beer. It even aged well after a year and didn’t go sour at all and cleared to a great clarity.


Wrap up

Sadly we know very little about the micro-flora that inhabit these trees, one study found 4 yeast and many unidentified bacteria, the more well known of those is found in cheese rind.  It wouldn’t surprise me if we even have the same wild yeast that has been used in sourdough bread. Hopefully future research will find out more before we lose these trees forever.

2014 Anderson Valley Boonville Beer Festival


This Year’s Theme:The Stone Age!

  • DATE: Saturday, May 3, 2014
  • TIMES: Taps open from 1:00 p.m. to 5:00 p.m.
    Music until 6:00 p.m.
  • PLACE: Mendocino County Fairgrounds
    14400 Highway 128, Boonville, CA
  • $40 Advance, $55 (Cash) at the gate