You might be thought mad to grow peas in your greenhouse, it’s often too hot and dry. Which is odd as most of our peas originated in Egypt before Biblical times. Indeed many are not hardy and could benefit being under cover during the colder part of the year. Just there’s the usual handicap of some crops needing a large number of plants to produce a portion or two at any time. You could tend a specimen pea plant but realistically you need a row to grow any quantity. And space, dwarf varieties of pea need but a foot or two, most climb up to head height, be warned some traditional sorts can reach 12 feet.
Alternatively there’s good value from Mange-tout varieties where you eat whole, raw or cooked, their wider, flatter pods. (Some varieties have fibrous edges / strings to their pods best removed.) Mange-tout or Sugar pea varieties are old European sorts which do not develop the tough parchment of ‘normal’ peas though their shells become tough, and if allowed to mature their peas can be shelled as ‘usual’. Their pods are flattened, often sickle shaped, and MUST be picked as soon as swelling seeds show. When continually picked clean the plants which can reach head height up canes will crop over a month or more, thus a tub or twos worth starting almost any month of the year.
However there’s another contender, a ‘newer’ Mange tout introduced from the USA, the Sugar Snap, and the very similar Snow pea from Asia (the one to sprout for pea shoots tou mio for stir fries). Sugar Snap pea pods do not swell wide and flat but thick and crunchy, and sweet. Tastier then Mange-tout, likewise must be picked regularly and often before the seeds become apparent. Though if missed and any ripen these could be shelled, but awkwardly. Of course leaving any to ripen slows production so be careful to pick clean then these can crop over a month or more.
Peas of all sorts are simple, just sow a finger length apart in rich free draining compost, in as large container as convenient, with suitable canes, and keep lightly watered, give more once cropping starts.
And if inexplicably suddenly no new pods form better find that ripening one!