Narcissus and Daffodil

84 G.R. Hanks
Hanks and Jones, 1986; cf. Allen, 1938). With increasing planting depth (8–23 cm),
Wallis (1964) reported that emergence and flowering were progressively later,
while bulb yields were greatest at intermediate depths. Narcissus bulbs can probably
be planted much deeper than this, although this would be suitable only for
garden and landscape use, where it would avoid damage from surface cultivation.
Hagiladi et al. (1992) planted Tazetta bulbs at depths up to 90 cm. Deeper planting
delayed emergence, and planting deeper than 60 cm resulted in fewer leaves and
a net loss of bulb yield, although some shoots emerged even from bulbs planted
90 cm deep.
Planting arrangement
When bulbs were planted by hand in beds, they were placed evenly, 1½–2 bulb
diameters apart and upright in the rows (Rees, 1972). Machine planting tumbles
bulbs into the planting furrow, so they are more-or-less randomly orientated
within the ridges, presumably resulting in less uniform growth and shape. The
effect of bulb orientation was investigated when planting machines were introduced
(NAAS, 1961; Wallis, 1964). Although random planting produced bulbs
with bent necks, orientation (vertical, inverted, diagonal or horizontal) did not
affect bulb yields, although vertical planting gave earlier crops. In the UK, ridges
are often arranged at distances of 90 cm, centre-to-centre, but 76 cm ridges are
also used. Planting machinery is often set to plant bulbs in a 20–25 cm wide band
within the ridge, so the actual planting density within the planted area (the planting
band) may be 3–4 times the overall (field) area. In trials, the width of the
planting band (20–35 cm) had little effect on percentage bulb weight increase or
bulb grade-out with planting densities from 20 to 30 t/ha (Millar, 1978; ADAS,
1983). In trials with bed-grown narcissus in the Netherlands, changes in planting
arrangements, from 95 cm planting bands in 140 cm-wide beds, to 105 cm planting
bands in 150 cm-wide beds, had practical advantages as well as allowing 2%
more bulbs to be planted in the same area with little impact on labor requirements
(van Dam and Schaap, 1987).
Rees et al. (1968) investigated the effects of planting density, rectangularity and
row orientation in bed-grown narcissus in south-west England. Density did not
affect anthesis date, but high densities increased stem length by over 20%. Flower
numbers increased with density, but the number of flowers per bulb fell at the
highest density. Lifted bulb weight increased with density, but did not peak within
the range of densities used in this experiment (up to 150 bulbs/m 2 ), although
yields of larger bulbs reached a maximum above 100 bulbs/m 2 . Bulb yields were
considered more than adequate, even at the highest planting density. Bulb yield
declined with increasing rectangularity in east-west rows, but was unaffected by
rectangularity in north-south rows, probably an effect of wind via shelter or light
interception. Plants in north-south rows had longer stems.
In trials comparing ridge- and bed-growing of offsets and double-nosed bulbs at
54–216 bulbs/m 2 for 1–3 years, also in south-west England, planting at 20–30 t/ha
gave the highest combined financial returns for bulbs and flowers (Wallis, 1968; Rees,
1972; Rees et al., 1973). Flower yield in the first year was directly related to density,
thereafter declining at the higher densities and with larger bulbs. Ridges were
out-yielded by beds by 26–29%, except at the lowest density where the difference