Agapanthus – The spreading menace

Because they have thick strong rhizomes that spread everywhere in the ground, it is almost impossible to remove permanently by manual means – thus it is usually a waste of time to try to dig them out.   Instead, you can treat with herbicide and then it’s job done.  There are two main ways to treat Agapanthus:

Option 1: Cut & Paste Method (For Heavy Clumps & Rhizome Blocks)

Where you have a large infestation and can easily access the crown roots / rhizomes:

• Recommended Gel: Apply Cut ‘n’ Paste MetGel (Metsulfuron-methyl) directly to the freshly cut rhizomes.
• Cut all leaf stems as close to the root crown or rhizome mass as possible using a sharp spade, loppers, or silky saw.
• Immediately smear a full-coverage layer of gel across all freshly cut stumps and exposed rhizome surfaces (within 15 seconds) so the active ingredient translocates deep into the underground root architecture.
• MetGel translocates through connected underground rhizome networks for maximum kill on tough, established clumps.

Option 2: Leaf Wipe Method (For Standing Foliage / No Digging)

If you want to avoid cutting or digging, apply herbicide gel directly to the active green leaves while the plant is intact.

• Recommended Gel: Apply Cut ‘n’ Paste Bamboo Buster (double-strength 240g/L Glyphosate).

• Technique: Put on nitrile safety gloves. Brush or wipe a generous layer of Bamboo Buster directly onto the underside of the active green leaf blades (covering 30–50% of the foliage per clump). Wiping the underside ensures optimal absorption through the leaf surface down into the root system without rainfall washing the gel off easily.

Stopping Re-Infestation & Follow-Up Care

1. Persistent Follow-Up: Agapanthus frequently resprouts from overlooked / missed rhizome fragments, and dense seed banks will reinfest bare soil. Plan for at least 3 to 4 follow-up inspections over the following 12 months.

2. Work Top-Down: When clearing banks, cliffs, or slopes, always start eradication at the top and work downwards to prevent seeds and rhizome fragments from washing into cleared lower areas.

3. Delay Replanting: Do not plant native species into the cleared site until you have completed 2–3 successful follow-up treatments and no new regrowth appears.

Important Notes:

• ⚠️ Safety Warning: MetGel and Picloram / Picloram Plus+ have significantly more residual soil activity than the glyphosate gels, and can move through ground moisture. MetGel has a soil half-life of roughly 30–90 days, and Picloram roughly 2–6 months, perhaps longer in clay soils. Do not use either near desirable non-target plants, within the root zone of prized trees, or around waterways and wetlands.
• When using MetGel or Picloram, never apply it inside the drip line (canopy edge) of prized trees or broadleaf garden plants. On flat ground, keep a 3 to 5-metre safety buffer. On sloping ground where the weed is uphill from desirable species, extend that buffer to 5 to 10 metres.
• Weeds often grow along streams and in gullies. If you’re working near waterways, use Bamboo Buster. Do not allow any weed gel to enter the water.
• Only treat weeds / target plants / trees that are on your property, or that you have permission to treat. Be aware that some species might have protection status or have a notable status, or be a designated scheduled tree under the district plan – if in doubt, check with your local council.
• Safety First: Wear gloves and protective clothing and observe all safety protocols, especially when using machinery, chainsaws and other tools.
• When using any herbicide ensure you READ THE LABEL THOROUGHLY, and follow all instructions and directions for the purchase, use and storage of the product.
• If in doubt, seek professional advice.