Cabbages belong to the Cruciferae family, so called because their flowers have four petals arranged as a cross. 
A cross with arms of equal length is a symbol of the sun.

In Irish folklore, cabbages are supposed to reveal a lot about a future spouses. 
Blindfolded girls were sent out in pairs to pull the first cabbage they could find. 
If there was a lot of earth attached to the root, they would have plenty of money but if there was only a 
little earth, they would be poor. The taste of the heart of the cabbage would reveal a lot about the future spouse's disposition - sweet or sour!

Sage, mint, thyme and rosemary all improve by being planted near the cabbage. 
When you plant your cabbage plants, plant a stick of rhubarb with them - this prevents club root. 
Twist a narrow strip of tinfoil round the roots of your cabbage plants to prevent cabbage fly.