Narcissus and Daffodil

98 G.R. Hanks
usually collected in 25 kg lots in nylon mesh bags. After grading, bulb storage
should continue under the conditions as before. It is usually advantageous to
organize bulb handling operations so that re-planting stocks move quickly to
HWT and planting, and bulbs for sales are separated and despatched promptly.
Where bulbs are being sold for growing on, inspection and certification may be
needed from the appropriate plant health authority. For example, in the UK samples
of bulbs are subjected to dry bulb inspection by the Plant Health and Seeds
Inspectorate to ensure freedom from soil.
In the case of narcissus bulbs being grown for processing, many of these steps –
which are aimed at producing visually attractive, healthy flowering bulbs for the
ornamentals trade – may not be applicable.
Long-term bulb storage
In commercial floriculture, long-term storage methods have been developed for
narcissus bulbs to facilitate transport to the southern hemisphere or to produce
very late flowers. Both warm and cool storage methods have been used (Beijer,
1957). Where bulbs are being supplied for processing, longer-than-usual storage
may be necessary to suit production schedules.
In retarding narcissus bulbs by warm storage, Dutch bulbs were formerly stored
at 28 °C and 70% relative humidity from lifting (in July) until shipping the following
year and planting in South Africa in August (Hartsema and Blaauw, 1935).
Long-term storage at extreme temperatures (–1.5 °C or 34 °C) was detrimental to
the bulbs, but good results were obtained by storage at 25.5 to 31 °C followed by
10 weeks at 17 °C (Hartsema and Blaauw, 1935). Beijer (1957) obtained best
results by storage at 30 °C from lifting to mid-October, followed by –0.5 °C until
late-December then 25.5 °C until shipping in February-March and planting in
April. For longer storage, 25.5 °C was used from late-November (Beijer, 1938).
Warm storage can be prolonged for a year, making all-year-round flowering
possible. This has been investigated with several standard cultivars (ADAS, 1970,
1989a; Tompsett, 1988). Bulbs were stored for several months from lifting at 26 °C
and 70% relative humidity, then at 17 °C for 4 weeks before being planted and
placed at 9 °C for 6 weeks; after this they were transferred to cool growing conditions.
The normal cold requirement did not seem to apply, but the 9 °C period
promoted root growth. The required flowering dates could be attained by ‘holding
back’ the plants at 2–5 °C as necessary.
Long-term storage of narcissus bulbs at low temperatures was investigated by
Griffiths (1936). Bulbs were stored at 1 °C from November for up to 10 months.
Vegetative growth was satisfactory, although the flower buds had died, indicating
that prolonged cold storage for non-cropping purposes should be satisfactory.
Beijer (1957) reported that bulbs could be shipped in September following storage
at 20 °C, then planted in November at 5 °C for 1 month and then at 0 °C until as
long as July, flowering satisfactorily. Alternatively, bulbs can be frozen at –1.5 °C
over winter and spring, planted and then stored at 7 °C for 3 weeks followed by
9 °C for 2 weeks and then 1 °C as required, flowering thereafter taking place in
4–6 weeks (ADAS, 1989a).
Transient exposure to sub-zero temperatures, during growth or after harvest,
damages many flower-bulbs. Cohen et al. (1997) investigated the hardening of bulbs