I want to make some Sahti however the recipes always say to use juniper branches. I cruised to the local garden center and noticed there are about a zillion and one different species/varieties of Junipers for sale. Should I look for a specific variety, or will any Juniper bush provide good Sahti?
Each species of juniper has a slightly different flavor to them so the best way I can answer is to try making some juniper tea with a few species if you can and pick the one that tastes better to you. Crush/break up 15-20 needles a bit to release the oils and let it seep in boiling water for 3-5 mins before you drink it. The best flavored tea will produce the best flavored Sahti.
I use what is easily available to me, but out of the 5 different types in my area, Juniperus communis and Juniperus monticola tend to work out best with my batches.
You should note that some of the Juniper varietes in the US are poisonous. http://www.nytimes.com/2008/03/20/garden/20qna.html?_r=0
In Finland we only have the Juniperus communis and Juniperus Alpina, so one of those is at least true to style.
Just be careful that all the pots and especially the kuurna is absolutely clean and hygienically ok. But one of the most crucial problems is where to get real sahti malt. Otherwise everything is rather easy, but maybe it should be pointed out that please, put the fermented liquid after one day of foaming in a place the temperature of which is around 7-8 C. And don't move the can! After two weeks you can taste. Then put sahti in smaller cans and into temp. around 3 C. Don shake the yest in the bottom, drop it away - Now you can enjoy perhaps the best rural beer still existant. (You can use hops and juniper as spice during the fermentation but only a handful is enough.) Welcome to Lahti next summer - we will demonstrate how to make traditional - and local - sahti!