Narcissus and Daffodil

Production of Narcissus bulbs 107
Figure 4.10 Narcissus ‘chips’ with bulblets at the end of incubation. (Photograph:
Horticulture Research International).
may form bulbils when cut at any time of the year, subsequent growth is best when
propagation takes place using ‘dormant’ bulbs in July or August (Alkema and van
Leeuwen, 1977; Hanks and Rees, 1978; Vreeburg and van der Weijden, 1987a),
and this also gives propagules that are ready for planting-out at a reasonably convenient
time of year. In earlier work, emphasis was on cutting many small twinscales
or chips per bulb in order to maximize multiplication, for example aiming
for twin-scales weighing 0.5–0.8 g (Mowat and Chambers, 1975) or cutting 16
chips per bulb (ADAS, 1985c). However, small propagules take four or more years
to produce bulbs of flowering size, and recent recommendations have been more
pragmatic, sacrificing numbers for bulbil size and a quicker production of flowering-size
bulbs: bulbs of 10–12 cm circumference (weighing about 40 g) are cut into
eight segments only (Vreeburg and van der Weijden, 1987a; Hanks, 1989).
Cutting rates can be adjusted to initial bulb size to achieve target bulb weights after
a year, after which bulb rate increase is independent of cutting method (Fenlon
et al., 1990). While cutting bulbs by hand is the only possibility in twin-scaling,
chipping machines are available which can increase throughput to about 0.5 t/day
(Flint et al., 1984; Zandbergen, 1984). Chipping machines are based on either a
star-shaped blade operated by a pneumatic plunger or on arrangements of circular
saw blades fed with bulbs or bulb halves on a conveyor. To avoid spreading
pests and disease between bulbs, and to minimize other contamination, sensible
hygiene should be observed when twin-scaling or chipping bulbs, including disinfecting
blades (Vreeburg and van der Weijden, 1987a). Immediately following
cutting, twin-scales or chips are treated by soaking in a fungicide, effective materials
including products based on captan and benomyl, often used in combination
(Vreeburg and van der Weijden, 1987a; Hanks, 1989; Linfield and Price, 1990).