Hawthorn

Azarola (Crataegus sinaica) and May (Crataegus monogyna)

Hawthorn

Image credit: David Stephenson

Azarola and May are species of Hawthorn and this is the term used here to describe them collectively. 

They are physically similar plants that invade native vegetation. Hawthorn is present in isolated infestations in the Mount Lofty Ranges but has the potential to become widespread.

Hawthorn (Azarola and May) is a declared weed under the Natural Resources Management Act 2004 (NRM Act).

Description

  • an erect, branching shrub or small tree that can grow to 7 m high and 7 m wide
  • branches are stout and armed with thorns up to 25 mm long
  • leaves are lobed and 1 to 6 cm wide
  • flowers are white, cream or pink and grow in flat-topped clusters at the ends of branches
  • fruit is red, globular and contains two or three seeds
  • seeds germinate in autumn
  • early growth is slow and plants do not flower until the second or third year. Flowering occurs in late spring to early summer, and leaves are shed in autumn
  • plants are long-lived, possibly for more than 70 years
  • reproduces by seeds and suckers
  • mature tree produces over 2000 fruits, each with 1 to 3 seeds
  • seeds have a dormancy of 2 or more years.

Impacts

  • impacts on bushland by invading the shrub layer of grassy woodlands
  • forms dense, spiny thickets that displace other shrubs and suppresses the growth of ground-layer plants
  • provides poor habitat for native fauna and reduces biodiversity
  • leaves dropped in autumn may increase nutrient levels in the soil and make it easier for other pest plants to become established
  • can provide good cover for rabbits and other pests
  • closely related to horticultural crops belonging to the rose family
  • overseas, Hawthorn species host the fire blight bacterium which affects pears and apples. Hawthorn is also known to host Mediterranean fruit fly and light brown apple moth.

Distribution

  • introduced to Australia as an ornamental plant and to form hedges
  • occurs mainly where annual rainfall exceeds 600 mm and invades watercourses in lower rainfall areas
  • a pest plant of roadsides, wasteland, poorly managed pastures and abandoned orchards
  • invades grassy woodlands
  • seeds are dispersed by farm machinery, vehicles, animals and agricultural produce
  • in the past, deliberate plantings have been the main cause of spread but now spread by birds is more important.

How to control this weed

  • most effective chemical treatment is to cut the trunks as close to the ground as possible and to treat the stumps with herbicide. Triclopyr has been effective when applied to cut stumps or basal bark
  • mature shrubs can be removed mechanically, but regrowth occurs unless all the crown and the top few centimetres of the main roots are removed
  • small plants are susceptible to spot spraying
  • seedlings can be hand-pulled
  • for advice on chemical control techniques contact your nearest Natural Resources Centre
  • refer to the 'Weed control handbook for declared plants in South Australia' for advice on chemical control. You can find it on the Biosecurity SA website.

Declarations

The following sections of the NRM Act apply to Hawthorn (Azarola and May) in the Adelaide and Mount Lofty Ranges region:

  • 175 (2) Cannot transport the plant, or any material or equipment containing that plant, on a public road
  • 177 (1) Cannot sell the plant
  • 177 (2) Cannot sell any produce / goods carrying the plant
  • 182 (2) Landowner must control the plant on their land
  • 185 (1) NRM authority may recover costs for control of weeds on roadsides from adjoining landowners

More information

For more detailed information download the fact sheet.

Please contact us for advice and assistance with controlling Hawthorn.

Natural Resources Adelaide and Mount Lofty Ranges