What does it look like?
Periwinkle is a scrambling groundcover plant that resembles a vine. The trailing stems can grow more than 2m long and take root where they come in contact with the soil. Its leaves are glossy, 4-10cm long, 3-7cm wide and arranged in opposite pairs on the stem. It produces blue-violet flowers that have 5 petals and are 4-5cm in diameter.
Periwinkle is a widespread escape from cultivation. It grows best in moist, shady places such as waste places, riverbanks, roadsides, forest margins, and shrublands.
Why is it a problem?
This species is fast-growing, tolerant of shade, and moderately tolerant of dry or wet conditions. Its creeping, layering habit allows it to form dense, long-lived stands. It can regrow after being damaged or grazed. Sussequently, it can dominate bare areas and outcompete native ground-cover species.
Periwinkle does not usually produce seeds but can regrow from fragments of roots and stems.
- Dig out very small sites. Dispose of plant material at a refuse transfer station or burn. Check for regrowth.
- Smothering: use black plastic or weedmat. Cover sites as they are, or rake into big rolls and then cover (6+ months). Hand-remove surviving plants.
- Weed wipe (all year round ): 500ml glyphosate + penetrant per 1L water.
- Spray (all year round): 200ml glyphosate (360g/l) + 1g metsulfuron-methyl (600g/kg) per 10L. Avoid use within drip line of susceptible species. Requires constant follow up. Apply twice a year, in spring and in autumn. Treatment is required for three or more years.
- Mowing: For level, easily accessed land, mow with lawnmower on very low setting, 2-3 times a year. As it regrows, follow up by grubbing remaining roots with grubber or shovel. Dry thoroughly then leave on site to rot down. Takes 1-2 years to eradicate.
CAUTION: When using any herbicide or pesticide, PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.