What's the difference between peas in the UK and in the US?

I've lived on both sides of the Atlantic and I've never noticed much difference in peas, but then I'm not a connoisseur. The UK generally has 2 kids of peas on sale on the store, regular peas (aka garden peas) and petit pois, which are smaller, younger peas. The petit pois are much sweeter than garden peas, which are bigger and less flavorful. I've never seen petit pois in the states as far as I can remember, but there are generally peas and "sweet peas", and sweet peas tend to be sweeter than regular peas. The UK also has a product called mushy peas where the peas are mashed up and served as more of a liquid - not as bad as it sounds, it can be tasty if done right. This would often be out of a can if served at home.

As for how to get your peas how you like them I'd ask whomever makes dinner in your family what type of peas are used and how long they are cooked. People in the UK used to boil vegetables until they practically disintegrated but cuisine has improved dramatically in the past decade and nowadays it's much rarer to get that.

I've only been to the UK once, and so my only basis on 'British' peas is 'mushy peas' for the most part. I do know that American varieties of fruits and vegetables are much more likely to be bred for sugar content as compared to European bred ones.

I suspect that most of what you were getting in the UK were 'hull peas', as another name for them is 'English peas'.

As I don't know how peas are classified in the UK (other than 'mange tout'), this is what I know for US peas (may be incomplete; I couldn't find an authoritative exhaustive list):

• snow peas : aka. sugar peas; available fresh or frozen, as a whole pod, almost flat with very little peas inside; you eat the whole thing (mange tout)
• snap peas : aka. sugar snap peas; available fresh in the spring and sometimes late fall. Sold as whole pods with large peas in them (sometimes so large they start flattening each other); you eat the whole thing (mange tout)
• hull peas : aka. garden peas, shell peas, English peas; available fresh in the spring as whole pods, but the pod is not edible. Some varieties are sweeter than others.
• field peas : aka dry peas; Used as a fall cover crop, and commonly sold dried or used as cattle field.
• peanuts : (might not be a pea; definitely is not a nut) : Bends over as it grows, so the pods grow underground. Can be sold fresh ('green peanuts'; highly perishable, only available in areas where it's grown) or dried ('raw peanuts'), but commonly available in the US in a cooked form (mostly roasted, but also fried and boiled (seasonal) in the US south)

And to differentiate by processing:

• fresh peas : it's possible that there are places that sell them already shelled, but around here I can only get them shell on, and can typically only get snow peas out of season.
• frozen peas : typically labeled as 'sweet peas' or 'petite peas'
• dried peas : I'm not sure if these are made from garden peas, field peas, or both
• split peas : dried peas that have had their skins removed and split in half; cook up similar to lentils
• canned peas : foul things; I'm not sure if they're really food; avoid at all cost

And then we have all of things with 'pea' in the name, but are actually different families of plants (I think they're all beans / legumes / pulses):

• pigeon peas
• black eyed peas (cowpeas)
• the 'peas' in 'peas and rice'
• chickpeas
• crowder peas
• cream peas

... and if anyone knows of any naming differences between the US and UK, please add it to Translating cooking terms between US / UK / AU / CA / NZ

My impressions from visiting is that peas in the UK seem to be let go longer before harvest and as a result become more starchy than sweet - they also seemed to be vastly overcooked on a regular basis (as seen from a USA perspective.)

From what I have been able to find is that marrow fat peas are what we call feeder peas. They have less sugar and are grown for animal feed but they are also grown and packaged as split peas in regular grocery stores. See Dry Field Pea