Cape Weed (Arctotheca calendula)
Cape weed is a broadleaf annual that forms large, flat rosettes across lawns, making it one of the more obvious and unsightly lawn weeds in New Zealand. It originated in South Africa’s Cape Province (hence the name) and is now widespread throughout the country, thriving in everything from sandy coastal soils to heavy, waterlogged clays.
In New Zealand conditions, especially where summers are mild and moist, Cape weed can survive for more than one season. It often appears after dry periods when lawn grass has thinned out, quickly spreading across open ground. Once established, it forms wide mats that crowd out desirable grasses and leave bare patches behind when it dies back.
Identification
Cape weed is easy to spot once you know its features. It forms a large rosette of jagged, lobed leaves that sit flat to the ground. The upper surface of the leaves is green, while the underside is pale and covered in fine white hairs.
In spring, it produces eye-catching flowers about 2–4 cm wide, with yellow petals and a dark purple centre. The flowers resemble daisies but with more angular leaves, which helps distinguish Cape weed from similar “flat weeds” such as dandelion or catsear.
Why It’s a Problem in Lawns
Cape weed quickly takes over weak or open lawns, spreading from a single rosette into a wide patch that shades surrounding grass. It thrives in dry, compacted, or low-fertility soils where lawn grasses are struggling.
Its seeds spread easily through mowing, animals, and foot traffic. Once the weed flowers, even a small infestation can seed thousands of new plants, making control more difficult the following season. In lawns, it’s mainly a visual problem—large pale rosettes that stand out sharply against green grass—but if ignored, it can dominate entire areas within a few months.
Control in Home Lawns
Cape weed is relatively easy to kill with the right herbicide but preventing it from spreading is just as important.
Best control methods:
- Physical removal: For isolated plants, dig out the full rosette before flowering. Dispose of it carefully to avoid spreading seed.
- Chemical control: Use selective broadleaf herbicides containing clopyralid (NZLA BWC), dicamba/2,4-D combinations, or picloram (NZLA Gold). These provide strong results when applied to young, actively growing plants in autumn or early spring.
- Avoid composting clippings: These herbicides leave soil residues, so do not use treated lawn clippings in compost or garden beds for several months.
- Cultural management: Strengthen the lawn to prevent re-establishment. Fertilise regularly, aerate compacted areas, and use drought-tolerant lawn cultivars to stop Cape weed taking advantage of bare soil.
Prevention Tips
- Mow infested areas last, especially while Cape weed is flowering, and clean the mower afterwards to prevent spreading seed.
- Overseed and feed lawns after dry periods to keep turf thick and competitive.
- Water deeply but infrequently to encourage strong grass roots.
- Maintain balanced fertility to prevent the open, stressed conditions that Cape weed loves.