Plectranthus

What does it look like?

Plectranthus is a trailing or straggling herb (occasionally subshrub) with stems covered in purple hairs that form runners and root at nodes. Hairy and oval textured leaves (5-12 x 3-7 cm) with serrated edges are in opposite pairs. They are purple underneath and dotted with glands. Erect stems (<30 cm tall) of tubular white flowers (1 cm long) with purple dots inside lower lip are produced (Dec-Aug), followed by small dark brown nutlets. It tolerates damp, moderate shade, and cool to high temperatures.

It spreads primarily by runners, and when moved around in soil or green waste dumping. It’s common in gardens. Seed is produced, however because they do not evolve for dispersal by birds, wind and water. The spread of this plant is primarily vegetative.

Why is it a problem?

Plectranthus creeps along the ground to form thick mats, similar to tradescantia, that prevent seedlings of native species from establishing, leading to eventual thinning of the canopy, and the area being opened up to invasion by other weedy vines and shrubs. It’s likely to invade damp shaded habitats, especially disturbed forest, shrubland, streamsides, river systems, fernland, and wetlands throughout New Zealand.

More information

Physical control
Pull up and dispose of at refuse transfer station, burn, or bury. This method can be used to minimise initial spray. Or, weed mat: leave 3-6 months.

Herbicide control

• Spray (all year round) with glyphosate (10ml/L + penetrant) or metsulfuron-methyl 600g/kg (10g/100L + penetrant (spraygun) or 2g/10L + penetrant (knapsack)) or triclopyr 600 EC (30ml/10L) or triclopyr 120g/L (15ml/L). Follow up within 3-6 months, and replant bare sites.
• CAUTION: When using any herbicide or pesticide, PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.

Related links

Plectranthus • Weedbusters

NPPA and the control of weeds | NZ Government