The below list is not exhaustive or rigorous. I’m no expert. The flowers I’ve thought of using will be added here as the blog progresses with a link to whether they may be edible or not. Just because one internet source claims they’re edible, I can’t be certain so proceed at own risk. While I don’t intend to eat the flowers directly but propergate yeast and bacteria from them, there may be a chance that any toxins leach out.
Gorse all year https://www.eatweeds.co.uk/gorse-flower-cordial-recipe
Blackthorn March/April http://www.naturessecretlarder.co.uk/wild-food-useful-plants/blackthorn-sloe-prunus-spinosa.htm
Cuckoo Flower (cardamine pratensis) March – August http://www.wildfooduk.com/hedgerow-food-guide/ladies-smock-1-hedgerow/
Dandelion April – May https://www.eatweeds.co.uk/nasreddin-tale-dandelion
Hawthorn April – May https://www.permaculture.co.uk/articles/many-benefits-hawthorn
Woodruff April – May https://en.m.wikipedia.org/wiki/Galium_odoratum
Broom April – July Sacred and Herbal Healing Beers
Yarrow late April – September http://www.countryfile.com/explore-countryside/food-and-farming/top-ten-food-forage-march-and-april
Also some are rare or unsubstantial so I haven’t included them above.
Buttercup family including Lesser Celandine and Wood Anemone http://www.gallowaywildfoods.com/lesser-celandine-edibility-distribution-identification/
Birdfoot trefoil http://practicalplants.org/wiki/Lotus_corniculatus
Woody Nightshade http://www.thepoisongarden.co.uk/atoz/solanum_dulcamara.htm