h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Where's the yeast in this recipie? When I've made it I always used a sachet of bread yeast, which works a treat. It usually evolves to cope with the sugar better over time too, so you can use a pint or so of a previous batch to kick start a new one.

Does the sugar ferment naturally in this version?

Yes , elderflower , like most fruit and grain already have a natural yeast that has been perfected over millions of years to suit it's target.

ensure clean , good condition flowers so as to avoid contamination by other bacteria.

Sour-dough bread is equally made from just flour and water. The yeast present on the grain is still present in the flour (provided it has not been bleached!) Once warm and wet it will start an active culture in about 24hrs.