Ajuntament de Barcelona

The bulbous plants

Mossèn Cinto Verdaguer Garden

    Those plants who have underground meaty organs as a food reserve are known as bulbous (bulbs, corms, rhizomes, tubercles and tuberous roots), which allows them to survive during the less favourable seasons of the year, sort of hibernating.

    The beauty of its flowers made them very used in gardening as a decoration plant.

    They are deciduous vivacious plants mainly, which means that, after blossoming, the plant has still green leaves which remain healthy for some time before turning yellow and dry. Therefore, the aerial part disappears and only the underground part remains, the bulb, in a latent state during the season less favourable to growth. In its inside, the bulb is active and gets prepared for the next season, waiting for a environmental conditions that will allow it to grow again and develop a new plant.


    Bulbouscan store substances for reserve, mainly carbohydrates, in several underground organs to that purpose, such as bulbs, corms, rhizomes, tubercles and tuberous roots.

    The bulb in a vertical underground trunk, short, disc-like, surrounded by enlarged leaves that accumulate the nutrients that will be used for the outbreak and growth of the aerial part. Bulbs are classified in tunicate or flaky: the former have a base surrounded by superimposed leaves, reminding an onion or a tulip, the leaves in the latter are interlaced, looking like roof tiles, and are meatier, as in the iris or Madonna lily.

    The rhizome is an underground trunk that usually grows horizontally, strongly some of the times, with a variable length and width, with the roots and herbs in the knots. Rhizomes keep growing until the old are replaced by newer ones which can cover quite a wide area. Some rhizomatous plants are lily of the valley, German iris, calla lily or Canna indica.

    The corm is an underground trunk, similar to the bulb on the outside, but with smaller and thinner leaves since the reserves are concentrated in the meaty trunk, from where the roots are formed. Some of the most known plants are saffron, freesia and gladiolus.

    The tubercle is an underground trunk, enlarged and rounded, without flakes or any other protection, that presents new ‘eyes’ on each blossoming. Unlike rhizome, it has a limited growth and a life span close to a year. Some of the most known tubercles are edible such as potato, Jerusalem artichoke and tiger nut, but some others are used in gardening, like cyclamen or begonia.

    The tuberous root is an expanded and enlarged one that accumulates reserves before losing its aerial part during the rest season. The gems or future sprouts are found in the neck of the trunk base. Apart from the edibles tuberous roots such as sweet potato, manioc or yam, which are highly appreciated because of its energetic power as with the tubercles, some are cultivated merely for decoration such as dahlia, clivia, the flower of love or buttercup.

    History and curiosities: 

    Besides its reproduction by seeds, some bulbous can also reproduce by vegetative reproduction with a new plant alike the original. Horticulturists take profit of this property to obtain new plants. Vegetative reproduction takes place by using a piece of the plant and it changes depending on the type of reserve organ.

    For the bulbs and corms, the small bulbs and corms formed around the main ones are taken appart and used as seed to get, after 2 or 3 years, a bulb big enough to blossom. Some bulbous produce the small bulbs in the aerial part of the plant. Such is the case with the Lilium.

    Rhizomes and tubercles are reproduced by dividing them into pieces that must have one or two shoots (eyes) each. Using each piece as a seed, a new plant will be born. 

    When talking about tuberosas roots, like the gems or sprouts in the closest part to the trunk, a longitudinal section is made, paying special attention so that each one has, at least, a gem or piece of the aerial part of the mother plant. They must be sown in well drained and ventilated soils, such as the sandy ones, to avoid the plants being rotten.

    Bulbous planted during the Autumn have their blossoming at the end of the Winter or mid-Sping (hyacinth, tassel hyacinth, daffodil, crocus, buttercup, tulip, crown imprial, freesia...). If they are planted at the beginning of the Spring, its blossoming will go from the end of Spring until mid-Autumn (begonia, dahlia, gladiolus, Canna indica...). 

    German iris
    German iris
    Canna Peruvian-lily German iris German iris Tulip Tulip