Narcissus and Daffodil

64 G.R. Hanks
pathogen-tested nuclear stock of narcissus have been described (Anon., 1993).
Commercial ELISA testing services for narcissus are becoming available (e.g.,
Monro and Johnstone, 1992). However, ‘virus-freedom’ may be difficult to define,
given the advances in virus identification and detection (e.g., Mowat et al., 1988a,b,
1989; Boonekamp et al., 1990; Langeveld et al., 1997; Sochacki et al., 1997).
Narcissus bulbs from glasshouse forcing are commonly reclaimed and can be
‘plant passported’ for sale, but such ‘ex-forced’ bulbs must be labelled as such.
Although they may be somewhat small and desiccated, if properly hot-water
treated and grown-on for two or three years, good growth should be obtained for
an economical starting price.
Bulb size and shape
Yields are mainly controlled by the grade of bulbs and their planting density.
Narcissus bulbs are graded by circumference, with bulbs of the middle sizes
(12–16 cm) being in demand for dry bulb sales and bulb forcing. Small bulbs
(10–12 cm grade) are considered good planting material, since their percentage
weight increase can be high. Large bulbs (>16 cm) are often re-planted in a stock
because they are said to ‘increase vigour’, and they have been shown to emerge
earlier and have larger flowers than small bulbs (Strojny, 1975). The presence of
many small, round bulbs in a stock may indicate declining vigour, and it has been
suggested that bulbs