In England agapanthus are a prized garden plant with their showy blue or white flowers in summer. In Northland, many people see them spreading and are alarmed enough to get rid of them!
This can be quite a mission! Many people cut off the seed heads as soon as the flowers have finished which will prevent the spread. The clumps, however, get bigger every year and so do the number of seed heads. While you are managing the seeds well while you own the aggies, think about what happens when you go. None of us will own our gardens forever and we have no control over the next owner’s vigilance over the agapanthus seed.
The roadsides look so colourful with their blue and white garb of summer – so why is it a problem? Many people do not realise that roadside clearance of the water table or drain is important to maintain the integrity of the road. No one wants to drive through flood water whenever there is heavy rainfall. The seal can be undermined with stray flood water too – and fixing this comes from our rates! The weeds in the drains are often sprayed as part of road maintenance. Agapanthus is usually not killed with these herbicides. When the other weeds are gone, agapanthus will just fill up the drain, and the water must go somewhere else – usually all over the road.
To kill agapanthus, you will need a sharp spade and strong back to dig out the rhizomes under the ground. The leaves and roots will rot down, but the rhizomes will need to be mulched – a lawn mower is often strong enough to do this. Then dry the mulch on the lawn. Alternatively, Brushkiller or dicamba herbicides can be used effectively at gorse rates.
Good substitutes to plant are; coprosmas – shiny green or variegated ground cover ones, pohuehue, or one of the many colourful groundcover grevilleas that are so hardy, do well in a dry spot and feed the birds without being weedy.
Weed Action Piroa-Brynderwyns can help with advice and herbicides for all your problem weeds. Email Sara on firstname.lastname@example.org or ph 0220104092.