....... ones most bought late will have been sitting in a warm shop and have long spindly shoots. You will be hard pressed to find decent seed spuds in March to plant straight in the ground
Agree with that but the solution is not to buy them from shops, buy them from the producers who sell to the shops. JBA seed poatatoes for example. All of the producers will have tip top storage facilitiies and the experience to utilse them to their best ability.
but some people, including myself, plant earlier than that and then protect the emerging growth from frost. I do it because I believe it gives me a head start
That's quite reasonable and understandable. But I would assume that the majority of us want to plant and let them grow without protection. Buy early if for early planting, buy later for normal unprotected planting time.
I've always seen seed potatoes out for sale in the first weeks of January so I don't think demand has anything to do with it.
Demand always has everything to do with it, if there's no demand then the seed potatoes won't sell. Consumer demand is why we have supermarkets selling only perfect looking veg with no taste to them. The consumer demands it, the profit is there and the seller responds to that.
And comiserations to those who buy early and then have their seed potatoes ruined by bad storage. The shops depend on you because you then need to buy more later on. It's the same with bedding plants, the garden centres love to sell them at easter becasue half of them will perish with the next frost.
Apologies if this post is a bit of a rant becasue it is! Selling tender plants and seeds too early in the season is a pet irritant of mine. Apologies!