Narcissus and Daffodil

Production of Narcissus bulbs 109
Production from seed
Production from seed is, of course, the method used by breeders, and is also
important for species that form few offsets. Narcissus breeders may sow seed soon
after collection, either outdoors or in a cold-frame, and germination occurs
somewhat unevenly in spring. Caldwell and Wallace (1955) reported that, under
natural conditions, seed of Narcissus pseudonarcissus germinated naturally in
November or December, while Wells (1989) stated that, when seed is sown outdoors
in early May soon after collection, N. bulbocodium types start to germinate in
late-August and germination continues through the winter, with N. pseudonarcissus
offspring perhaps not germinating until early spring. Under natural conditions,
summer drought may induce dormancy in N. pseudonarcissus (Barkham, 1980).
Rees (1972) stated that narcissus seeds have a cold requirement of many weeks,
and Linfield and Price (1986) germinated seed of commercial cultivars using a
cold treatment of 12 weeks at 12 °C. Thompson (1977) reported that, in N. bulbocodium,
conditioning imbibed seed for 7 weeks at 26 °C (but not at 6 or 16 °C) gave
rapid germination when subsequently moved to 5–16 °C. This suggested that seed
should be sown in a warm glasshouse and moved to cooler conditions after 2
months. Hanks and Mathew (1997) reported that synchronous germination could
be obtained in N. cyclamineus, N. bulbocodium var. citrinus and N. pseudonarcissus by
keeping imbibed seed at 25–30 °C for 8–12 weeks then transferring to 15 °C.
There is little information on other aspects of the seed physiology of narcissus,
although Caldwell and Wallace (1955) reported that seeds of N. pseudonarcissus
were not light sensitive. Hanks and Mathew (1997) reported that controlling seedborne
fungi on N. cyclamineus by disinfection, HWT, etc., was difficult. Under
optimum conditions, it takes 3 years for seed-raised plants of species such as
N. bulbocodium and N. triandrus to reach flowering size, 4–5 years in other species
and 7–8 years in some cultivars (Koopowitz, 1986; Oldfield, 1989). This long
period needed to produce saleable bulbs is a strong disincentive to commercial
production. Germination and growing systems for the commercial production
of Narcissus species were investigated by Hanks and Mathew (1997), who showed
that seedlings could be successful raised in cellular trays for sale as ‘plug plants’
or for growing on, a method useful for species like N. bulbocodium that reach
flowering size quickly.
CONCLUSIONS
This chapter demonstrates that the methods for growing and handling narcissus
bulbs are well documented, but that there remains considerable scope for changes
in husbandry and other practices that might make the crop more cost-effectively
produced when growing for processing, or which would enable it to be grown in
an more environmentally friendly way. Some major research needs are evident,
such as the need for cultivars resistant to base rot and virus diseases (or their
vectors), for safer and (or) more effective chemicals (e.g., for bulb disinfection and
the control of large narcissus fly), and for the development of mechanical or
robotic bulb handling and sorting to reduce labour inputs. The transformation of
narcissus bulb production seen in the UK in recent decades has demonstrated