I think you're a little confused here, guest.

The hardy plant which has flowers which look like a scented sweet pea is called Lathyrus latifolius and its common name is 'Everlasting Pea'. This plant needs to be cut back to its base at this time of year. It's a herbaceous perennial.

Sweet peas that are grown annually for cutting and because of their scent are called Lathyrus odoratus. They finish flowering in about September/October and then I cut off the plants at the base and remove them from their supports. They are hardy annuals.

And hardy annuals don't regrow next year. That's it - finito, but some self seed and grow new plants from seed that was scattered the previous year.

You could also buy some packets of seeds & sow them now, transplant them to small pots, better still, grow them in toilet paper or kitchen towel (cut in 1/2) tubes to avoid disturbing their roots. These can be planted straight into the ground, in their flowering positions, in the spring & you will get bigger, stronger plants with more flowers than if you sowed them in the spring.

Iwouldt rely on results from like say Nastursions which somehow always seem to selfseed year in and out. Choose avariety or two and you can sow now or sow next spring.My way is to grow them on in acoldframe or the porch windowsill,I find they dodge the slugs and snails better.