What does it look like?
There are four species of privet in New Zealand: tree privet (Ligustrum lucidum), Chinese privet (Ligustrum sinense), privet (Ligustrum ovalifolium) and common privet (Ligustrum vulgare). Tree and Chinese privet are common in Northland, and both are pests.
Tree privet is a small-to-large evergreen, hairless tree up to 15m tall with distinctive lumpy warts on the stems. It has dark green leaves (5-13 x 3-6cm) that are glossy on the top surface and arranged in opposite pairs on the stems. Tiny fragrant, cream coloured flowers are produced from November to March, followed by bluish or purplish-black berry-like fruit (6 x 5mm).
Generally present in or near sites of human habitation, where they have been planted as hedges or specimen trees. Tree privet inhabits most coastal and lowland forest types (intact and disturbed), shrublands, fernland, cliffs, and coastline.
Why is it a problem?
Privet produces many highly-viable seeds in widely-dispersed berries. It is very dominant, spreading dense carpets of seedlings that displace native shrubs and prevent native plant regeneration. Privet is very tolerant of shade, frost, damage, grazing, all well-drained soil types, high to moderate temperatures, damp or drought conditions, salt and wind. Tree privet is long-lived; Chinese privet is short-lived but constantly replaced.
These species flower at different times of the year between July and March, with the flowers followed by berries that contain high numbers of viable seeds. These berries are dispersed through the autumn and winter months by birds or by falling from the tree. The seeds can germinate without the removal of berry flesh, but have a relatively short seedbank and are not likely to be viable after a year.
- Pull or dig seedlings (all year round). Leave on site to rot down.
- Stump swab (all year round): glyphosate (250ml/L) or metsulfuron-methyl 600g/kg (5g/10L + penetrant).
- Bore and fill (all year round): 1 hole /20 cm of trunk, 2 g/hole of metsulfuron-methyl 600g/kg.
- Frilling: With a sharp chisel or axe, make a deep cut into the sapwood at regular intervals around the base of the tree, taking care not to ring-bark the plant. Immediately saturate the cuts with metsulfuron-methyl 600g/kg (5g/10L + penetrant).
- Injection method: Holes are drilled sloping into the sapwood at regular intervals around the tree. Immediately saturate the holes with metsulfuron-methyl 600g/kg (5g/10L + penetrant) or undiluted Tordon Brushkiller, using a sheep drench pack with spraygun.
- Spray (spring-autumn): metsulfuron-methyl 600g/kg (5g/10L) + penetrant.