Water requirements for Watercress

[Mamsoth]

I've just started some watercress seedlings in little cubes of rockwool and am going to grow them in a pot filled about halfway up with hydroton and a solar powered pond aerator to keep the water oxygenated. Can I just use straight tap water to fill the pot (I live in the south east with quite hard water, calcium content of 293ppm). Or should I use filter water? Or is there a better option altogether?

Is anyone growing watercress at the moment, what sort of water are you using?

[ameno]

That set up seems like overkill, to be honest.
Watercress doesn't need flowing water or oxygenated water, or even to be in water at all. It just need very wet soil.
Last time I grew it, I just grew it in a pot with a compost/soil mix, which I then placed in a bucket and filled the bucket with water to about an inch from the top of the inner pot. That kept the soil saturated with water, and it did very well (until cabbage whites ate it all).

It's not that picky about water type, I think. Although in the wild it usually grows in chalk streams, so if anything your hard tap water may be better than rain or filtered water (although rain water is still fine).

[Jungle Jane]

I live in Essex,water straight from the tap smells like chlorine here,I always let it sit in the watering can overnight usually but thirty minutes at least,I don’t know if there’s a specific amount of time for chlorine evaporation. Good luck with your seedlings.

[burnie]

Watercress is usually grown as an annual sown in the spring from seed, this time of year it tends to die off.
https://www.thompson-morgan.com/how-to-grow-watercress

[ameno]

I live in Essex,water straight from the tap smells like chlorine here,I always let it sit in the watering can overnight usually but thirty minutes at least,I don’t know if there’s a specific amount of time for chlorine evaporation. Good luck with your seedlings.

Chlorine should all evaporate within 24 hours, or you can boil the water in a kettle and it should all disappear in one go.
That's chlorine, though. Some water companies use chloramine, which is a chlorine-based compound and is far less volatile than chlorine, and thus takes a lot longer to evaporate. If you want to remove chloramine then your best bet is campden tablets (one tablet in 20 gallons is enough).
Yours is likely to be chlorine, though, as you can smell it. The odour is proof that chlorine is evaporating from the water, which wouldn't happen with chloramine.

[jdlondon]

I grow mine outside in the ponds and they love it. Spreads like crazy. One has a fountain but the running water doesn't seem to matter, both grow well.

Also, they're from store bought watercress, rooted in a glass of water inside before planting out in waterpots with lots of gravel mixed in with the soil. They did do well just placed in a container with water halfway up, but without a doubt, nowhere near as well as in the ponds.

Caterpillars love it, I was picking them off constantly and even then they ran riot over them - but the watercress just came back quickly and abundantly, so it wasn't a problem in the end.