The soil in the summer cottage is not always suitable for growing plants, but they still need to be grown. Such a simple idea will help out.
It’s not very difficult to make a box of boards yourself, fill it with an earthen mixture of suitable composition, install arcs from reinforcement on them. Plants planted in such boxes can be covered with a film to protect against low temperatures, shaded with an opaque fabric from the scorching sun - in general, use any material.
In such greenhouses, hotbeds, you can sow tomatoes in early spring and not transplant them later. They will give a better crop than transplanted crops, since they avoided a sharp change in temperature. And to care for plants in such conditions is much easier than planted in the open ground ..