You'd have to make your cuts very big to get over the plants. Thanks for every ones comments I'll come back later in the year & let you know how I get on.
You lay the covering on the ground, make X shaped cuts in it, peel back the flaps, and put the plant roots / tubers etc into the soil through the covering. You don't put the plants in first and then waggle the covering over the plants.
No what I meant was in reply to
if i take the polythene off in the autumn once the plants have established themselves ,and the weeds have slowed down, do you think that would be ok for the soil
Thats when the crosses would have to be big to get over the plants