Have planted melons plants (and two ridge type cu's) in a polytunnel (the 'Sauna' as it has been dubbed by Junior.....) about 10 days ago - when the plants out grow the polytunnel (about end of next week at current growth rate! ;D) will i be ok removing the polytunnel or should i extend it to cover the vines? Any offers of advice appreciated!!
If the polytunnel is accessible to bees I would leave it in place until the fruit is about to ripen- that way you won't ripen the entire crop in a few days. If the bees can't get to your plants then you should certainly leave it on until just before the female flowers are starting to open (probably a week after the males).