I'm going to test the feeding plants artificial sweeteners thing. One friend suggested using saccharin as the sweetener because its chemical structure is pretty different from that of plants (unlike sucralose or aspartame maybe) which would make it harder for the plants to process and more likely for them to store away the sweetener somewhere. Another friend suggested using radishes because the flavor change would be quite clear and they grow quickly. Checking dates, radishes take 20 to 30 days to mature while the first boston frost probably isn't until october 5th, which means I still have leeway.