Narcissus and Daffodil

Production of Narcissus bulbs 83
Figure 4.6 Effect of planting density, bulb grade (offset or double-nosed (DN) bulb)
and crop duration (1, 2 or 3 years) on profitability. Data for narcissus
‘Fortune’ grown in ridges, from Rees et al. (1973), with permission from
The Journal of Horticultural Science and Biotechnology.
High planting densities may accentuate problems with pests and diseases, create
handling problems at planting and lifting, and require changes in irrigation or
fertiliser practices. Planting density has a large effect on the spread of base rot. Linfield
(1987) placed healthy bulbs 0, 10 or 20 cm laterally from ‘inoculator’ bulbs,
and after one growing season 60, 27 and 6% of the healthy bulbs were affected,
respectively. The base rot fungus can infect bulbs 30 cm away (Price, 1975c).
For all bulbs to be at risk of infection requires 10% affected bulbs at a density of
10 t/ha, but only 5% at 20 t/ha, on ridges 76 cm apart; lower percentages would be
required using 90 cm ridges (Tompsett, 1980a).
Planting depth
Narcissus bulbs are usually planted about 13 cm deep (from the base of the bulb to
the top of the ridge). Taking care to adjust machinery to ensure an even planting
depth, especially on undulating sites, produces a uniform environment and aids
bulb lifting. Deeper planting may produce better growth, but bulbs are harder to
lift, while shallower planting may lead to damage from cultivation and herbicides,
and the bulbs are in warmer soil. Narcissus bulbs have contractile roots, and planting
bulbs 20 cm deep results in the typical bulb shape, whereas when planted at 5
or 10 cm deep bulbs become elongated as a result of root action (Tompsett, 1977;