Hi, I have learnt a lot about cucumbers in the last few months, due to having many problems with mine! Have a read of my thread, as in the pic my unhealthy plant looks a bit like yours!
Cucumbers!
Have you over watered it or got the leaves wet? Or sprayed anything on the leaves? I made the mistake of spraying the leaves with soapy water as this apparently kills greenfly, however it nearly ended up killing the whole plant off! The advice I was offered was really helpful and now I have two very healthy looking cucumber plants! The golden rules it seems are...
* Don't get leaves wet
* Don't water too near to the stem (I've made a little hollow in the soil at the edge of the pot, and pour water into it a little at a time
* Don't over-water (I wait until it looks thirsty and soil is dry)
* Feed once a week with plant food / tomato food
* Use liquid seaweed at least once a week til it picks up and after, it has picked up many of my plants from the brink of death! Vitax organic liquid seaweed is available from wilkos and isn't expensive.
Hope that helps a bit! Even if it's none of those things I mentioned, definitely give it a good dose of liquid seaweed stuff! Good luck
