What does it look like?
The leaves of this plant are composed of subdivided leaflets, giving it a fern-like appearance during its vegetative state. The leaf stems (petioles) are hairless and often display a purplish tinge. Hemlock flowers are white, each with five petals and no sepals. The flowers are arranged in clusters on highly branched stalks, which can reach up to 8 feet (approximately 2.4 metres) in height.
Poison hemlock is a biennial species. In its first year, it forms a basal rosette, which is notably bushier than those of many other plants and can grow up to 40 cm tall and wide. In the second year, the plant produces tall, erect, and highly branched flowering stalks. At maturity, poison hemlock can reach up to 2 metres in height. The stems are smooth, hollow, and distinctly marked with purple or pink blotches, which are key identifying features.
Why is it a problem?
Every part of this plant, especially the fresh leaves and fruit, contains a volatile, oily alkaloid, which is so poisonous that it can cause birth defects and death of livestock.
Control methods
Physical Control
Pull or dig out plants (all year). Remove all plant material so stock don't eat it. Mowing or slashing flowering plants will only provide temporary control.
Chemical Control
- Young hemlock plants can be treated with 2,4-D or flumetsulam without harming most other pasture components.
- Larger plants are best controlled by spot spraying with a herbicide such as glyphosate (100ml/10L) or metsulfuron 600g/kg (1g/10L) or triclopyr 600EC (50ml/10L). Remove all stock from the area as plant material will become more palatable after spraying.
- The plant will quickly become succeeded by taller native species, so only control in open or sensitive areas.
- CAUTION: When using any herbicide or pesticide, PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.
Related links
Management Programme
Unwanted Organism
An unwanted organism is any organism that's capable of causing harm to natural or physical resources (like forests and waterways) or human health. A number of introduced pests in New Zealand are classed as unwanted.
