I will be in for it after you read some of these. (tin hat ready) More in depth evidence is available so i can back them up.
Crocks in pots improve drainage.
The verdict False: a drainage layer in the bottom of pots reduces the volume of soil available to plant roots. Don't add gravel or crocks, but ensure pots have drainage holes.
Watering in the middle of the day scorches leaves.
The verdict False: watering in bright sunlight does not cause sunburn, but it does waste water and can create problems with fungal diseases.
Urine speeds up composting.
The verdict False: urine may be beneficial in composting if there is not enough fresh, green material in your heap, but it will not speed up composting in a balanced heap.
Parsnips taste better after the first frost.
The verdict True: parsnips really do taste sweeter after being exposed to the cold. To enhance their flavour, leave roots in the ground until you need them.
Coffee grounds keep slugs at bay.
The verdict False: coffee grounds may not deter slugs, but they are high in nitrogen, so put them on your compost heap instead. Spraying plants with a caffeine solution equivalent to a strong cup of coffee does kill slugs!!!
Pea and bean roots left in the ground improve the soil.
The verdict False: picking peas and beans removes most of the nitrogen that was gathered by bacteria in root nodules. Put spent plants on your compost heap to harness any nitrogen left in the leaves.
Tea is a good fertiliser for pot plants.
The verdict False: regular watering and an occasional liquid feed are better for plant health than relying on tea. Used tea leaves are best added to your compost heap.