Raised planters

Are they standing on grass/soil or on concrete?

I think this sort of container is great for salads and that kind of thing, especially if they are in the garden at home rather than in the Lotty some way away.   I've used this sort of thing at home myself.  I'd use it for some radishes and spring onions a couple of different lettuces and a cucumber or two.  I'd refresh the compost about 50% and use a bit of BFB or growmore during the season.  You could probably keep yourself adequately supplied with some of these crops throughout the season with a bit of industry and planning