Blue spur flower
Botanical Name
Plectranthus grandis
Family
Lamiaceae (mint)
Also known as
plectranthus
Where is it originally from?
East and South Africa
What does it look like?
Soft-wooded, strong-smelling upright shrub (<2-3 m tall). Large, downy, soft, broad (6-20 x 4-13 cm), oval leaves with coarsely toothed edges and rounded tips with small sticky glands on underside. Tubular deep blue flowers (20-25 mm long) in whorls of 4-10 (Jan-Dec), on erect purplish stems (20-50 cm tall), are followed by tiny brown nutlets (May).
Are there any similar species?
Plectranthus ecklonii has purplish-blue flowers, is less woolly. P. barbatus.
Why is it weedy?
Tolerates semi-shade, damp, and high to moderate temperatures, but is frost tender. Moderately long-lived.
How does it spread?
Produces few seeds, spreading mainly by stem fragments through soil movement and dumping of garden waste.
What damage does it do?
Forms dense stands, stopping native plants from establishing. Shades out smaller native plants and scrambles over other plants. Dense growth can restrict access to bush areas.
Which habitats is it likely to invade?
Heavily disturbed bush and shrubland, and bush margins, especially in northern areas.
What can I do to get rid of it?
1. Dig out small patches (all year round): dispose of at refuse transfer station, burn or bury.
2. Cut trunk and paint stump (all year round): cut trunk near to the ground, and swab freshly cut stump with metsulfuron-methyl 600g/kg (1g/L) or glyphosate (200ml/L) or triclopyr 600g/L (100ml/L).
3. Overall spray (all year round): metsulfuron-methyl 600g/kg (2g/10L) + penetrant; or glyphosate (100ml/L) + penetrant or triclopyr 600g/L (30ml/10L).
What can I do to stop it coming back?
Easy to control. Follow up within 3-6 months to kill resprouted stems. Replant bare sites.
