What does it look like?
Hawthorn is a deciduous shrub or small tree that can grow up to 10 m tall. It has much-branched, hairless stems that are reddish-brown when young and turn grey with age, bearing stiff spines up to 12 mm long. The hairless, triangular leaves (35–50 × 35–45 mm), with 3 to 7 deep lobes, are solitary on long shoots and clustered on short shoots. They are often chewed by slugs.
In October and November, dense, flat clusters of 6 to 15 sweet-scented, white (occasionally reddish-pink), five-petalled flowers (10–15 mm in diameter) appear. These are followed from December to April by round, shiny, crimson berries (7–11 mm in diameter) that contain a single stone surrounded by little flesh.
Why is it a problem?
Hawthorn produces many long-lived, well dispersed seeds that can be spread by birds, water or soil movement. It’s extremely tough and versatile, long-lived, tolerates hot to cold temperatures, damp to dry conditions, salt, wind, heavy damage, most soils, and semi-shade.
Hawthorn out competes most other species, forms dense thickets, preventing the establishment of native plant seedlings and forest regeneration. It is most likely to cause issues in disturbed forest, shrubland and margins, fernland, wetland margins, short tussockland, other low-growing habitats, and cliffs.
Control methods
Physical control
Dig out small plants (all year round) and leave on site to rot down.
Herbicide control
- Stump swab (all year round) using metsulfuron-methyl 600g/kg (5g/L) or triclopyr 600 EC (50ml/L) or a product containing 100g picloram+300g triclopyr/L (250ml/L). Or,
- Cut and squirt (all year round): Make 1 cut every 100 mm around the trunk, apply metsulfuron-methyl 600g/kg (2g mixed into a slurry with water) to each cut. Or,
- Injection method: Drill holes sloping into the sapwood at regular intervals around the tree. As each hole is drilled place glyphosate (250ml/L) or a product containing 100g picloram+300g triclopyr/L (undiluted) into the hole using a sheep drench pack with spraygun. Or,
- Frilling: With a sharp chisel or axe, make a deep cut into the sapwood at regular intervals around the base of the tree, taking care not to ring-bark the plant. Immediately apply 1.5ml of undiluted a product containing 100g picloram+300g triclopyr/L to each cut using a paintbrush or a squeeze bottle. Or,
- Spray (full leaf and actively growing stage only) using metsulfuron-methyl 600g/kg (7.5g/15L (knapsack) or 35g/100L (spraygun)). Full coverage of foliage required.
- CAUTION: When using any herbicide or pesticide, PLEASE READ THE LABEL THOROUGHLY to ensure that all instructions and safety requirements are followed.
Related links
Crataegus monogyna • New Zealand Plant Conservation Network
