Abstract: A kit for a knockdown greenhouse which is easy to assemble and ship in a conventional parcel service container is disclosed which includes a plurality of base strips for forming a rectangular base frame having first and second parallel side base members and first and second end base members. The base strips have a length generally equal to or less than the length of the container. First and second side base members have a series of anchors spaced along a length of the base members. A plurality of elongated bendable rib sections are included having a length generally less than the length of the container. Couplings are provided for joining ends of a predetermined number of the arch sections together generally end to end to form an arch-shaped rib whereby a plurality of arch-shaped ribs may be constructed. The arch-shaped ribs have first and second anchor ends which are interconnectable with the anchors of side base members to position the arch-shaped ribs upright.