Narcissus and Daffodil

The biology of Narcissus 5
Figure 1.3 Left: transverse section of single-nosed, flowering-size narcissus ‘Carlton’ bulb
in autumn. Right: diagram showing the generations of bulb units with their
component parts. Shaded areas: the terminal (above) and lateral (below) units
with next spring’s leaves and flower (individual bulb scales, leaves and flower
not shown). The unit that bore last spring’s leaves and flower comprises the
flattened remains of the stem (cross-hatched), three leaf bases (the innermost
semi-sheathing) (stippled) and two bulb scales (unshaded). Beyond these scales
are the remains of bulb scales and leaf bases of previous generations of bulb
units, which are eventually shed as dry tunic (broken lines). (After Hanks (1993);
reprinted from The Physiology of Flower Bulbs, ©1993, page 466, with the permission
of Elsevier Science.)
The narcissus is a perennial branching system, and Rees (1969, 1972, 1987)
used the term ‘bulb unit’ to describe each annual increment of growth, thereby
distinguishing these structures from shorter lived entities such as the bulbs of
tulip, where new bulbs (daughter bulbs) become separate entities each year. In narcissus,
the growing point produces a new bud with bulb scales and leaves each
year. This bud grows through its first year, and (if large enough) initiates a flower
in its second year, its leaves and flower emerging in the next spring. Thereafter its
‘scales’ persist for perhaps two more years, so that the bulb unit has an overall lifespan
of about 4 years. Since new buds are initiated in the centre of the bulb, the
bulb ‘scales’ are gradually displaced outwards by the continued annual production
of new bulb units within. In the year that a bulb unit reaches anthesis, its ‘scales’
(swollen with reserves) make up the bulk of the fresh weight of the ‘bulb’; subsequently
its ‘scales’ become depleted until they form the dry tunic (skin) of the bulb,
and they are eventually lost through displacement from within or by abrasion (the
latter accentuated by commercial bulb handling). Although bulb units may be
called ‘mother bulbs’ in the year they reach anthesis and ‘daughter’ and ‘granddaughter
bulbs’ previously, better terms might be pre-floral, floral and post-floral
bulb units. What are termed ‘bulbs’ in common usage might be better called ‘compound
bulb units’ or, more simply, ‘bulb clusters’. A useful diagram showing
narcissus development was presented by Alkema and van Leeuwen (1978) and is
reproduced in Figure 1.4.