So, here are my experiences with bog myrtle (
Myrica gale, aka sweet gale) in simple SMaSH-ish ales. Every August I visit somewhere that has bog myrtle growing wild - interestingly it seems to be closely associated with abandoned settlements up on the moors, it's almost like they were deliberately growing the stuff. So the last two years I've harvested a carrier bag or two on the last day, frozen it overnight, then transported it in an insulated bag (probably just about defrosting) and then kept it in the freezer for a few weeks until brewing. In 2017 I froze whole branches, in 2018 I had more plant and less room in the freezer, so I stripped the leaves off the branches and put them in a Tupperware box in the freezer. So in what follows I'm referring to whole "fresh" leaves out of the freezer.
My first comment would be that there seem to be big vintage variations. 2017 was a cool, overcast year and the bog myrtle smelt wonderful as I picked it - rubbing the fresh leaves they smelt of APA - all those citrussy/piney notes. It's not surprising once you look at the essential oil - it's dominated by 40-50% limonene or 1,8-cineol (eucalyptol) which convert into each other via terpineol, plus chunks of pinene, linalool, eugenol etc - all pretty familiar from hop chemistry. However, in 2018 I was picking after 2 months of record-breaking heatwave and the fresh leaves were far more subdued, they didn't have much smell to them at all. Maybe I was effectively picking much "older" leaves even though it was the same time of year as 2017, thanks to the ageing effect of the heat, I don't know. People don't seem to talk much about vintage variation for bog myrtle, but it's a real thing (as it is for most crops at high latitudes).
In both cases the base beer was 1.045 100% Fawcetts Maris Otter with about 20 IBU of EKG @60, then 6g/l (10/0/WP/dry) of Aramis (2017 - French lager hop that tastes of Kronenbourg) or Junga (2018 - Polish hop that has a bit of Saaz & Cascade to it but fainter. Still, it would be useful as a dirt-cheap hop in a house golden ale for BMC drinkers or to distract your mates from your special beers.). I deliberately wanted to try some of the obscure Euro hops, and didn't want anything too "characterful" distracting from the bog myrtle.
The original intention with the 2017 batch was to split two ways - with and without BM in the kettle, then take a litre out of each and dry-BM the rest. But I had a disaster with a leak which led to the non-BM wort getting thrown in an unsanitised bucket and it got contaminated. So I ended up just doing the one trial - my notes are a bit hazy, but it looks like about 2.5g/l (1.67oz/5USgal) in the boil and 1g/l dry-BM. Fermented with 1968. The results were really striking - the main body of the beer was quite smooth and honeyed with gentle bitterness and a hint of ?eucalyptus? but as you got down the pint I realised my tongue was going numb. If you've had Tyrozets, tablets which use benzocaine anaesthetic for a sore throat, it had a similar numbing effect as that.
This year I went for an 8-way trial, partly to test Windsor vs Omega Voss, but with and without a BM tea and with and without dry-BMing. First though I made a simple BM tea - boiling BM for 10 minutes in my very soft tapwater at a final volume of 71g/l. It was delicious! OK, you missed the malt a bit but otherwise it was very reminiscent of a 40 IBU APA. So I made a bigger volume of 10-minute tea and mixed in the first for a final mix of 130g/l. This was obviously stronger (65 IBU?) and had a hint of tongue-numbing. I diluted it into a bottle of Becks that was lying around, you could start to taste it at about a 1/10 dilution. So that's what I added to the "boil" arms, and then I dry-BM'd with 10g/l.
Life then got in the way, and they ended up in the fermenter for a month before bottling. Then when I was moving them, I managed to drop them and smashed about a third of the bottles, including all the Voss-BMboil-nodryBM samples. But to cut a long story short - the BM boil samples did fill out the mid palate with some pleasant flavours and moderate bitterness, the dry BM samples didn't add much beyond a slight antiseptic finish when they were young which then faded somewhat.
So 13g/l boil + 13g/l dry of 2018 bog myrtle seems to be adding a little more bitterness but far less tongue-numbing than 2.5g/l + 1g/l of 2017 bog myrtle.
Vintage must play a big part in this - I could feel that 2018 was going to be disappointing as I was harvesting it. But there's obviously lots of process variation in what I did above - 2017 was frozen on the branches whereas 2018 was stripped before second freezing, 2018 was boiled as a separate tea rather than in the wort in 2017, 2018 had longer than it should in the fermenter. And maybe I just misrecorded how much I used last year - but I don't think I was that far out, I didn't pick that much.
It's well worth making a tea, and diluting it into beer to see what it's like. But 70g/l 2018 bog myrtle tea is delicious on its own if you like your tea beery! 10 minute boil is probably too long, but boiling BM gives the nice beery flavours. Dry BMing is probably optional-to-discouraged, unless you like those eucalyptic/antiseptic/menthol kind of flavours, and it looks like it's the dry-BMing that makes your tongue go numb depending on the vintage. I might put leaves through the blender before boiling next year.
So that's that - with the disclaimer that BM is meant to cause miscarriages and was allegedly the hallucigen that made Vikings go berserk, so you should avoid it if pregnant and in general not have a lot of it.
