What does it look like?
Rhus tree (or Japanese wax tree) is a small deciduous tree or large shrub that is highly toxic and allergy causing. The tree reaches a maximum height of 8-12m and has small branches with leaves arranged in pairs along these branches with one terminal leaf. Leaves are 4-10cm long and 2-3cm wide, and change from their bright green colour to orange/scarlet in autumn. Very small yellow-green flowers form along new leaves in spring and early summer. The plant produces pale brown papery fruit that remain hanging in clusters on the tree through autumn and winter and fall in spring.
Rhus trees commonly populate areas of coastal indigenous vegetation, urban gardens, and wasteland. Tolerates a wide range of soil types. Can be invasive in disturbed sites, forests, open woodlands, urban bushland, roadsides, gardens and waste areas in temperate and sub-tropical regions.
In Australia the tree is known to invade disturbed areas of woodland and roadsides, and spread from domestic gardens into surrounding urban bushland.
Known to be scattered throughout Northland, particularly in urban gardens. Appears to be naturalising in parts of Northland currently. In the Bay of Islands, it is now growing on roadsides between Haruru Falls and Opua, where there are currently in excess of 50 juvenile and adult trees (approximately 15 adults and 35 juveniles). There are adults and seedlings in gardens in Russell, and it is also starting to occur on roadsides there. It is also present in gardens from Riverside to Onerahi in Whangarei, and seedlings are appearing in other gardens and on roadsides.
Why is it a problem?
Rhus tree is considered a noxious weed in some states in Australia, and is no longer sold in nurseries there. It is a serious weed in Sydney, where birds spread the seeds, and thousands of seedlings were found in home gardens, public areas and in urban bushland.
Rhus trees produce clusters of brown fruit that contain large numbers of seeds, which are primarily bird or gravity-dispersed, though also easily relocated by human movement of soil. The seed remains viable for many years, and will germinate readily, with seedlings usually found near the parent tree. The tree may also reproduce vegetatively by suckering.
Rhus tree can cause a severe allergic reaction to humans if skin contact is made, especially with the sap.
Note that physical removal of trees is not recommended as this species has high associated risks of poisoning including that from old branches and leaves, making disposal of the plant material difficult also. Stem injection of herbicide is recommended.
- Drill & fill/stem injection; Glyphosate 360 g/L undiluted 1–2 mL per cut
- Stump paint; apply a 3–5 mm layer of gel for stems less than 20 mm. Apply 5 mm layer on stems above 20 mm .
- Picloram 44.7 g/kg + Aminopyralid 4.47 g/L (Vigilant II ®)
- Glyphosate 360 g/LRate: 1 part glyphosate to 1 part water