Mary Fisher wrote:

You didn't specify "poking plastic" originally. Is that what you'd do?

Yes. I use the same principle in my veg patch. I cover it with old
silage sheet and make holes with a blow lamp. The sheet melts back to
produce a hard ring and a nice clean hole to plant the veg through. It
is quick and easy to do and I was simply transferring the same idea to
the polytunnel (scaled down, of course). I have some old poly somewhere,
I'll give it a try.

--
Howard Neil