Would a triangle of stakes with two rows of rails around them be any good , say the stakes five foot long knocked in to 18 inches deep with the rails 10 foot long made of cut saplings.
The sapling being smack bang in the centre of the triangle of stakes . That way it would be a post and two rails cheaper than a square enclosure .
I guess you still need to use a plastic wrap around tree guard to help stop the rabbits & hares stripping or eating the saplings
If you notice any damage use cheap 22 mesh chicken or sheep stock wire round the outside of the rails and staple it in place .
Hmm,
just had an alternative thought , how many of the black Dalek compost bins will your local authority sell you at residents rates. I've got seven for a tenner each delivered . two long stakes walloped inside from opposite sides ,following the angle of the sides should hold them in place or perhaps use three equal spaced stakes instead .
Then drill and tie each bin to each stake to keep them in place on windy days.
If you think that the bins are too dark , use a hole saw in a power drill to put a couple of dozen evenly spaced two inch dia holes in the sides so it looks even more Dalek like .
I guess it all depends on the money available .