Moth plant

What does it look like?

Moth plant is a fast-growing vine that can reach up to 10 m tall. The twining stems release a milky sap when broken. The leaves are arranged in opposite pairs along the stems. Topsides of the leaves are a dull, dark green with greyish-downy undersides. The white flowers are bell-shaped and may have some pink on them and are about 25 mm across. Distinctive, large pear-shaped pod (about 10 cm long) are produced, containing numerous tiny, fluffy seeds that can drift long distances on air currents.

Because moth plant originates from tropical countries like Brazil, Argentina, Paraguay, Uruguay, it can grow in almost any frost-free habitat. This includes intact and disturbed forest, forest margins, tracks, cliffs, riparian margins, shrublands, and islands. It’s also a problem in urban reserves and gardens where it can spread quickly. It prefers loose, fertile soils in warm, wet areas. It establishes most freely in semi-shade but will tolerate exposure to full light once it reaches the canopy of shrubs, hedges, or trees.

Why is it a problem?

Moth plant can rapidly smother and replace native vegetation, preventing regeneration in a range of habitats. It easily overtops shrubs and small trees, weighing and breaking them down. Because it’s tolerant of shade, drought, damp, wind, salt, and germinates in many soil types, its dominating seedlings often out compete smaller native plants. Moth plant spreads easily over long distances by wind due to its prolific seed production.

Moth plant seeds are poisonous, and the plant defends itself from insect damage by leaking milky sap. This sap can cause contact dermatitis in humans and can block the feeding parts of butterflies, leading to eventual starvation and death.

Control methods

Because this is a poisonous plant with sap that can irritate the skin on contact, always wear gloves when controlling moth plant (eye protection if the vine is above your head).

1. Hand-pull seedlings (all year round).
2. Cut vines that are too large to pull close to the ground and treat with stump paint/stump swab (best in summer-autumn), using a product containing 100g picloram+300g triclopyr/L (100ml/L) or a product containing 200g 2,4-D+100g dicamba/L (200ml/L) or dicamba 50g/L (400ml/L). Vigilant gel or Kiwicare Weed Weapon gel work well for stump swab work.
3. Remove all pods. These should be double-bagged and disposed of in your household waste or at a refuse transfer station. Leave remaining cut material on site to rot down.
4. Foliar spray (summer-autumn) where the infestation is beyond manual control, use a product containing 100g picloram+300g triclopyr/L (30ml/10L) or a product containing 200g 2,4-D+100g dicamba/L (12ml/L) or dicamba 50g/L (24ml/L).

Watch our video on how to control moth plant

More information

• Moth plant is becoming more established across urban Napier and Hastings areas but is far less established outside of these city centres.
• Moth plant is not published as a pest in the Regional Pest Management Plan 2018-2038, but it is an organism of interest.
• Moth plant is gazetted as an unwanted organism by the Ministry for Primary Industries.
• We will control moth plant at our discretion, but effort is being focused outside of the urban centres.

Related links

• NZ Flora
• NZ Plant Conservation Network
• Unwanted Organisms Register
• Weedbusters
• HBRC's Regional Pest Management Plan