A device for decorative purposes, for the vertical cultivation of plants, includes: i) a cultivation support containing a cultivation substrate, and having holes on the front face thereof for the opening out of the above-ground part of the plants, ii) a rigid frame extending in a substantially vertical plane, defining a window in the front face of the cultivation support, and iii) a water reservoir, the cultivation support being placed over the water reservoir, and including at least one hydrophilic wick extending from the cultivation substrate to the water reservoir tank. The cultivation support is hydrated by a continuous supply of water by one or more hydrophilic wicks immersed in the reservoir. It may include an internal framework to give it rigidity and to prevent settling of the substrate in the lower part of the support. A method for obtaining such a plant box is also claimed.