I bought some seeds from Ipomoea aquatica and would like to grow them in a container submerged in my pond as an annual flower, not for food. The plant is not invasive in my country as it is to cold during winter.

How are the seeds germinated?
Do I have to nick or soak them?
What soil is best?
When they have germinated, can I put the pot into the pond?
How deep should the water be over the crown?
What temperature should the pondwater have?

Many questions but I hope to get information from this forum.

Generally, Ipomoea aquatica is not kept in pots. It's best left alone to float on top of the water as it is designed to do. Water needs to be warm, probably 65?F-75?F at least.

if sown like other vegetables or flowers, I sow them in seedkompost in trays, when young plants, I put them into pots.

My waterlilies are in pots submerged in the pond.

Do you mean that I shall take the young plants ( in case they have grown) out of the trays and throw them into the water, just like that?

;)

You must have more of an Asian population than most cities in this country.

i soaked my seeds for a day and planted it the following day. result was ok

i cut and grow them since then and they are close to picture perfect

Interestingly, this was the broader-leafed "water ong choy", which is supposed to be harder to grow on dry land than the other, narrow leafed variety. Yet it was growing just fine.

The Chinese gentleman I spoke with seemed quite surprised that I had believed it needed to be grown in water.

Since then I've read (in Oriental Vegetables, by Joy Larkcom) that a raised bed system is actually the usual method of cultivation in China. Other interesting points - the veg does best at 77 degrees Fahrenheit and above, is killed by frost, and in general grows poorly when temps are under 50 degrees F. In northern areas with shorter days - such as Europe - the plants may be driven to flower prematurely and to stop producing good leafy greens. In this case you should remove flower buds from the plant in order to keep it growing (unless you're trying to save seeds). Also, apparently you get better results with seed grown plants than with cuttings (though cuttings are very easy).

Unfortunately, seeds are very hard to come by in much of the US. Even so, the plant is grown commercially here, I guess in states where it is legal, and I once read an article in a Texan paper (Dallas or Austin) about how ong choy is a great summer green, with seeds available in the local Asian stores of Texas.