CarolC - I'm not Wolfgang, but I have a basic grounding in scientific method - will i do?

Whenever an experiment is carried out which examines what is usually thought of as paranormal (and in many "normal" experiments too), an extra protection against fraud or unconscious bias is usually employed, called blinding. In your case, what this would mean would be that the person doing the weighing of the plants has no knowledge of which condition each of the plants has grown in, until after the results are recorded. Also you would need to make sure that you have sufficient numbers of plants to determine if there is a statistically significant effect (a power calculation would be needed here).

Anyone else got any methodological problems with Carols experiment?

Bagpuss