It comes from America where they tend to have dry winters and spring. There is no need to soak any 'tuber' in the UK or most of Europe as we tend to have wet springs as they will get all the moisture they need naturally.

I see. Thank you for this interesting opinion. Well, we have had dry winter this year, at least we call it like that as we didn t have piles of snow, but the soil is wet. So you think I do not need to soak for instance Anemones tubers?

You can soak them as it is interesting to see the Anemone tuber swell but it will naturally do that from moisture in the garden soil.

Delphinium tends to be supplied as bare root - I would not soak them at all but bury them lightly with a potting mix.

Thank you very much, Botanic.

soaking helps remove the dormancy hormones [ cant for the life of me remember their name!] allowing them to start into growth. If they have been in the ground all year they have slowly lost the chemicals. If kept in dry storage the soaking helps kick start the process. Moisture is need for the transport of chemicals through the tuber /seed too as all transport is done in solution.

Hi Seaburngirl, but what about wet soil and spring rains? For instance today I planted tubers without soaking them before that, because the soil is wet and there will be some showers this weekend. What do you think?

Dormancy hormones on bare roots and anemone tubers? I think you are confusing them with seed.

Aha.

No I'm not Botanic, there are growth promoters and restrictors present in tubers/etc so they don't grow at the wrong time of year. I remember having to study conditions that encouraged/inhibited growth in both seeds and other perenating organs as part of my degree.
As for plants like delphiniums the point of soaking a root ball is to ensure the plant has a good water content/ balance before planting. Planting often damages the fine roots and the root hairs that the plant uses to take up water.

If the soil is wet then the plant tissue will take water up Katrina.

Thank you very much to both of you for your points of view. My God, I am speaking in rhymes.