What to plant in a shallow trough with no drainage holes?
I have recently moved into an apartment which has a built-in, plastic-lined trough on the terrace which is only 20cm high (see below). I would not be able to make drainage holes. I'm a total gardening novice and at a complete loss at what to plant here.
I'd ideally something that looks aesthetically striking and that would grow as tall as this situation allows - I was thinking rough horsetail but not sure if that would need more height? It's a west-facing terrace on the first floor, and the trough gets a lot of afternoon sun.
Our downstairs neighbour has had some success with bruxus, agapanthus and woodland sage but I would prefer not to plant bruxus as we have a lot of box blight in our area.
Any help would be hugely appreciated!
I'd ideally something that looks aesthetically striking and that would grow as tall as this situation allows - I was thinking rough horsetail but not sure if that would need more height? It's a west-facing terrace on the first floor, and the trough gets a lot of afternoon sun.
Our downstairs neighbour has had some success with bruxus, agapanthus and woodland sage but I would prefer not to plant bruxus as we have a lot of box blight in our area.
Any help would be hugely appreciated!

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https://www.gardenersworld.com/plants/10-plants-to-grow-in-bog-gardens/
If you live in Derbyshire, as I do.
Without holes - you can't grow plants, even bog plants. They still need a certain amount of drainage or the soil will be stagnant.
I live in west central Scotland - not where that photo is...