[Stree]

Firstly, I realise that growing cress  is very easy, just a damp spot on a tissue and some light will do the trick but here is what I would like to do.....
I have some old stone sinks, none of them are very deep and the shallowest is only about an inch and a half deep......I would love to use these for growing in because they are a lovely feature, but the lack of depth is a major restriction............But cress is shallow rooted, at least baby cress, I do not intend to thin out and grow as cress salad leaves, if I do they can be planted straight into the soil.
I would welcome opinions and advice on what growing medium would be best for these shallow sinks, for the cress specifically.

[Yorkie]

As cress is an annual, multipurpose compost should be fine.  Make sure you have sufficient drainage, it'll just become waterlogged if no plugholes (or similar!)

If the sink is more than a few inches deep you might want to consider raising the surface of the compost up a bit so that the cress isn't too shaded and gets some light.

Alpines are often used for stone sinks, or houseleeks (not edible), just can't remember the latin name after 3 glasses of wine  :blink:

[Stree]

Sempervivums, and I had those in before. and saxifrage, which both did well, as did aubretia and violets. but I want to grow cress this time. there is drainage, each sink has a drainhole  and non are deep enough to cause any shade problems,
My concerns are the retention of moisture in such a shallow container. Would something like perlite or vermiculite be helpful in this, mixed with the compost of course.
Thanks for the reply Yorkie, sounds like the compost is a good base medium .

[Stripey_cat]

Perlite and vermiculite tend to increase drainage, in my experience.  Lots of organic matter, or those water-retention crystals will help.