This mainly involves removing excessive branching in the middle of the plants. After manual harvesting, plants should be pruned to clear excessive growth from the centre of the shrubs to facilitate ease of harvest in the subsequent season. Allowing light into the centres also allows new growth and flower buds to develop. Spraying is essential to contain the leaf hopping insect, psyllid, which is the major pest problem. This minute insect causes the plant to take on a rusty appearance, followed by honeydew and then sooty mould on bushes.
Heavy infestations eat away the developing flower buds and can severely reduce yields.
Harvesting and extraction In New Zealand at present all harvesting for oil extraction is done by hand with a picking comb. Care is required to remove only flowers as leaf and stalk material have different chemical components to the flowers. Early morning harvesting is best because the flowers become sticky as they warm up and are then much more difficult to remove from the bushes. Heating occurs quickly in the flower bulk and this must be avoided. Research has shown that flowers can be stored at this temperature for up to 12 days without deterioration.