Auckland Botanic gardens

Bulbous plants have storage organs at or below the soil surface. These features have evolved over millions of years to allow the plants to survive extended periods of environmental stress such as cold, heat or drought. Carbohydrate and nutrient reserves are stored in these organs to support re-growth of shoots, roots and flowers.

What we know as 'bulbs' may be true bulbs, corms, tubers, tuberous roots, rhizomes, stolons or pseudobulbs:

True Bulbs (such as Amaryllis, daffodils, tulips, and garlic)

True bulbs contain a short, fleshy vertical stem enclosed by thick modified leaves, usually termed scales. Bulbs produce side branches, called bulblets or offsets.

Propagate by separating the offsets when the plant is dormant, replant with a good dose of compost.

For more information on bulbs see our Bulbs page 

Corms (such as Gladiolus and Crocosmia)

Corms are modified stems which are enclosed by dry, scale-like leaves.

Again, propagate by separating offsets, called cormels, from the primary corm. 

Dig up the corms after flowering, separate and replant the small offsets (Cormels) with some compost. Cormels usually require an additional one to two years of growth before flowers are produced.

Tubers (such as Dahlia and potatoes)

Tubers are modified, underground stems with nodes and lateral buds (eyes).

Harvest tubers after shoots have died back. Propagate them by either re-planting the entire tuber or cutting the tuber into sections. Each section should have 1-3 eyes.

 

Rhizomes and stolons (such as canna lilies and iris)

Rhizomes and stolons are modified horizontal stems. Rhizomes grow just below or at soil level, while stolons grow horizontally above the soil surface.

Divide rhizomes and stolons to multiply plants. Ensure there is a vegetative bud in each piece. Generally, divide at the beginning (spring) or near the end (autumn) of the growing season.

 

Pseudobulbs (such as orchids)

'Pseudobulb' means false bulb and refers to modified stems used for food storage. They are commonly produced by orchids and vary significantly in appearance. 

Divide by separating from the parent plant and transplanting. It is best to separate off the newest growths with a couple of older pseudobulbs attached. The best time to divide is immediately after flowering or just as new roots start to develop.

Succulents

Offshoots or pups are terms used for offsets of some succulents that develop and form roots at the base of the mother plant. These can be carefully removed and potted up or replanted directly into the garden.

For more information on succulents, see our Succulents page.