Bulbs and corms

Bulbs

Botanically speaking, a bulb is a short underground stem which is covered by enlarged and fleshy leaf bases which contain stored food.

Bulbous plants gradually die down after flowering and store up food in these underground stems, they then remain dormant until their new growing season, when they use the stored food to grow upwards again. It’s important not to cut the leaves off bulbs as soon as they have finished flowering – they need to keep their leaves to enable them to photosynthesise and build up the food store, otherwise the bulb may not survive the dormant season.

Bulbs may have a papery ‘tunic’ around them to protect them from surface damage or drying out, the presence or absence of this can help to identify bulbs. Bulbs without tunics are more susceptible to drying out. Here are some example bulbs sorted by whether or not they have a tunic:

• With a tunic
  • Onion (Allium cepa)
  • Daffodil (Narcissus)
  • Tulips (Tulipa)
  • Hyacinth (Hyacinthus)
• Without a tunic
  • Lily (Lilium)
  • Fritillaries (Fritillaria)

Bulbs often produce ‘baby’ bulbs – bulblets or bulbils – which can be separated from the parent plant and grown as new plants. Bulbs can also be cut into sections, or the fleshy leaf scales separated, in order to obtain more plants. Please see our propagation information for more details.

Corms

Corms are similar to bulbs, but their structure differs slightly. The bulk of a corm is made up of fleshy stem tissue, which stores the food. It is surrounded by relatively thin leaves.

Examples of corms include:

• Gladioli (Gladiolus)
• Crocus
• Cyclamen

As with bulbs, corms can produce tiny corms, called cormels, which can be divided from the parent and grown on. Please see our propagation information for more details.