Purple asparagus has a huge advantage over its green relative - it doesn't end up stuck in your teeth.

It is also sweeter than the green stuff and this, combined with the brighter colour makes it attractive to children. Purple foods are popular with health-conscious consumers because the colour indicates a high level of health-enhancing anti-oxidants (which reduce the risk of cancer). The purple plant has one other advantage - eating too much green asparagus can turn urine green but its dark-coloured cousin is blameless.