What causes cucumer leaves to go green/yelllow around the edges?

[Nick Blair]

Is it caused by too much water or lack of water? What should I do?

[Nick Blair]

I mean white/yellow around the edges.

[burnie]

Could be sun scald,if under glass try a bit of netting to shade them.

[Nick Blair]

Oh its under plastic.

[taff]

under plastic/glass, same thing really, they're both used for the same kind of thing,to keep the temp up.
It's more likely to be sun scorch. If the edges are damp in the morning then the sun comes and does it's burning thing, the edges will go yellow/white and papery.
If it's quite a big plant rather than a seedling, it's more likely to be down to watering and/or feeding.
Again,if it's a big plant, the leaves at the bottom do that after a while anyway, no need to worry just yet
If it's a little plant,do as burnie suggested, shade it a bit so it's not in direct sunlight all the time.

[Nick Blair]

Done that, but things began growing on the brown part, so I had to pull a large portion of the leaves off, hopefully they will recover and not die.