Reality of those green-fingered myths

MYTH: Put coffee grounds in the garden to fertilise your plants and reduce waste. REALITY: Caffeine and polyphenols in coffee may be toxic to plants and worms. Coffee grounds can be beneficial, but only if they’re composted first to reduce levels of chemicals. MYTH: Use vinegar to turn your hydrangeas blue by making the soil more acidic. REALITY: It would take a few bottles of vinegar, which could harm hydrangea roots, so it is better to use aluminium sulphate. MYTH: Tidy up daffodils by tying up their leaves after the flowers are gone. REALITY: This may mean an inferior display of daffodils next year, as it damages leaves and hampers photosynthesis. MYTH: Stake a newly-planted tree or shrub to protect it from wind, which can tear the roots. REALITY: Wind stress encourages trunk thickening, so staked plants may be thinner and snap or be uprooted. MYTH: Improve water drainage by covering holes at the bottom of plant pots with pot shards (‘crocks’) or gravel. REALITY: This can waterlog plants, as water flows more quickly through potting compost.