Gosh. Yes, they will certainly be bushier if nipped. someone else will probably have more exact advice, but if it was me, I'd nip half for now, and the others in two or three weeks time.

Hi Buckley, are these in a heated greenhouse ? If so get them out asap. They might have gone a bit leggy now, but you will get something following Sheilatubs advice. If you try some more, once they germinate, get them to a cold frame or somewhere similar, they are very hardy, only protect from frost, if necessary.

Sheila'tubs' - love it! Re sweet peas, nip them out, make bushier plants, and harden them off, taking advantage of this (relatively) milder weather. Worthy

Hmmm, you might Worthy. Bit close to the bone for my liking. :)