By Facet_edge
United Kingdom 
Every year our cucumbers end up looking like this. The discolouration slowly climbs up the plant which then dies.
The plants are watered twice daily approx 5 litres each time.
We have tried growing in the soil and this year in pots but it makes no difference.
10 Jul, 2011
Answers
Thanks for the reply.
We thought maybe growing them in pots would be OK but they still look pretty sick.
Will try changing the soil next year.
I think it's too late for them this year!
15 Jul, 2011
it looks like a deficiency of some kind - magnesium or more likely iron - since they eventually die. Is the soil very alkaline? if it is think about getting some topsoil in to replace that in your greenhouse. quite often over the years indoor soil can get very stale - especially if humus-rich materials are not added. you can use sequesterenes too - but i think it would only be a stopgap. Once you have new siol make sure you add well-rotted compost and/or a good mulch of comfrey - it is important to feed the soil as well as feeding the plants! Good luck
10 Jul, 2011