Earthing up simply draws up the soil around the plants. Potatoes are earthed up to prevent tubers turning green and inedible with the toxin solanine.
Earthing-up also helps protect them against blight.
It helps protect against frost damage. Newly emerged foliage can be protected by earthing-up the soil around the shoots.
When young stems are about 9 inches high (23 cm), start drawing soil up to the stems and covering to produce a flat-topped ridge about 6 inches high (15 cm). Preferably this is done in stages, little and often.
Earthing up can also be beneficial to brassica like brussels sprouts, which can be top-heavy and have to survive the winds of autumn.
- leeks, celery and florence fennel are earthed-up to blanch the developing stems or bulbs.