We all know them, those big blue flowers seen in the garden often doing a great job covering a bank. In rural areas they often grow wild and uncontrolled on roadsides particularly in drains and water courses. 

Look closely and they can be seen in views of coastal scenes looking somewhat out of place.  Yes, most people know the large forms of agapanthus, in particularly agapanthus praecox, sometimes known as the African lily or Lily of the Nile although it is not a lily at all.

A native of South Africa, it is loved by many gardeners.  It does a great job of holding sloping ground together and smothering weeds.  It is a hardy plant and is a great survivor that requires little maintenance or watering once established. What’s more, it puts on a great floral show with large, bright blue blooms.

Unfortunately, it is these very properties that are offside with some governing authorities which would like to see this form of agapanthus controlled if not eradicated. 

The former Auckland Regional Council defined a “Regional Pest Management Strategy” which among other things classified agapanthus praecox as a “surveillance pest plant” and deemed it as having a significant impact on the biosecurity values of the Auckland region. 

What does this mean?  It means this big blue flower cannot be propagated for sale in the Auckland region.  It also means, landowners who have these plants are encouraged to remove them to help protect the environment.

However, for those who loves its beauty and can’t live without it in the garden, it is possible to prevent its unwanted spread. 

The number one thing to do is to remove the seed heads once it has flowered. agapanthus seeds prolifically and grows from seed readily. It is not enough to just cut off the seed heads and leave them on the ground. It is thought the seeds will continue to ripen in the severed seed pods.  The seed pods must be removed and destroyed.

On the other hand, those who decide to remove the plant altogether will have a challenge. 

In small areas they can be dug out but be sure to remove as much of the root system as possible. 

Be mindful of how the plant material is disposed as it will likely grow again if deposited on the ground.  Monitor the area for re-growth in the future. 

Chemical spray control is possible. Along with your chemical spray, a spray additive, designed to help the chosen chemical penetrate the plant’s waxy leaf covering, will enable the chemical to get into the plant and do the work required of it. 

For the best chemical control options consult a specialist at your local garden centre, farm supply store or visit the still active ARC website (www.arc.govt.nz) for recommendations. There you will find ample information including chemical control methods.

Love them or hate them, agapanthus praecox are well established and here to stay. They may look great in the garden but do the foreshore and bush fringes a favour and help limit the spread of this intrusive plant.