Greenhouses, Sheds and Sun Rooms - Greenhouse Frame 2x4's?

We are building a 10ftx16ft greenhouse. I was going to use 4x4 post for the frame but money is kind of tight but i want something more then a pvc greenhouse. Instead of the 4x4 size can i use 2x4's? I would have the 2x4 in the ground with concrete for the supports and frame the roof with 2x4's. I would have 11 2x4 support posts. I just wanna know if the whole frame is made out of 2x4 if it will be sturdy enough. We are going to be using heavey duty plastic sheeting.

THanks
Matt

2x4's are not sufficiently treated for ground contact. I would suggest 4x4 posts at the corners and one 4x4 midway on each side. Then use 2x4's above ground to frame the structure.

I agree with wirepuller. Years ago (30), I was thinking greenhouse. I researched (library) some books, and saw old time farm buildings - barn, etc., with how to . One was a pigs' barn. Made with a 4x4 bottom rail on each side, with 1x2's attached, each bent to an arch. With 1x2s running horizontally, spaced every 2' apart, that kept the staves inline. One end framed a door, the other a solid wall. Install thermostat fan in gable end, high up. I guess it was popular at the turn of the century. (Minus the plastic roof and fan.) Be safe, GBR

And I wouldn't put ANY wood in the ground, treated or otherwise!!

Pour a slab and attach your framing to that. That's permanent. Something less permanent would be to build a wood floor on pier blocks, and attach your framing to the wood floor.