Ancient varieties of high protein (gluten) wheat which were well-suited to old-fashioned slow proving sourdough breads with natural yeasts. More modern spring wheats can't make enough protein for that process hence Irish soda bread which is fast and involves neither yeast nor proving. It seems some of the old varieties may have survived in various heritage seed banks.
That’s very interesting ! I make bread in the bread maker and soda bread in the oven ! So I use different types of flour , but I’ve never tried sourdough
A very interesting link @Obelixx this bit especially was interesting /Irritating!
Fintan [Keenan] gets proteins of 16.1 per cent in his wheat in Denmark,
I's impossible to buy flour over 12% here and we're told that we cannot sell our (Denmarks) wheat outside of the country because the quality is so poor (low protein) which is put down to the very strict limits on fertilisers.
As to a sourdough it's easy enough to start one and there are many guides on how to do it. I've been using mine for a couple of years and it just started with flour and water sitting on the counter for a week. However mine is rye and is used only for rye bread, that may make a difference.
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a neighbour has pulled out bunches of it and offered it to me ! It looked a bit too rampant .
sword like leaves from tiny bulbs
https://www.irishtimes.com/life-and-style/food-and-drink/our-daily-bread-ireland-s-grain-growers-and-millers-1.3612824