Just a few thoughts from this side of the Atlantic, Smoke / ash: smoke and ash from veld fires has a profound effect on the germination of certain seeds and it seems to have an effect (unproven of course) on mass flowerings of certain plants such as Aloe and Cyrtanthus (our 'fire' lilies) - this could also be due to other factors such as higher light levels, less competition, etc., after the fire has removed most of the surrounding vegetation. Nitrates: lightning activity 'fixes' atmospheric nitrogen and makes it available to plants at leaf and root level. Acidity: rainwater typically has a pH of 5 or less (acidic) due to the absorption of atmospheric carbon dioxide - domestic water (well water?) is more than likely to be alkaline in reaction (pH>7). Any other ideas? Regards Rogan. Please find our Email Disclaimer here: http://www.ukzn.ac.za/disclaimer/