when to separate/thin seedlings?

[sheeshshe]

OK, so I had the 20c seeds and the lettuce germination rate was terrible, so I wasn't sure how the cucumber germination rate was so I planted 2 per cell. well, it figures they all came up LOL! so.... when should I separate them? what is the optimal time? when they're small, 1st set of leaves, second? when I put them outside? or... a friend said she'd just leave them that way. what is the best option?

[Bobberman]

If they are very small seperate them and plant as soon as you can. Once they get bigger I would plant them together without disturbing the roots and simply cut the top off of the weakest plant!

[jal_ut]

I am with your friend. Just let them both grow. They will do fine.