Bryonia cretica ssp dioica
Where is it originally from?
What does it look like?
Soft, summer-green, cucumber-like vine (<6 m tall) that dies back in autumn to a huge, branching, brittle, perennial tuber (45-160 x 100-800 cm), oriented vertical to horizontal. Soft slender stems with coiling tendrils arise from the end of the tuber, with thin, 5-lobed leaves (<15 x 15 cm), with the middle lobe being the longest. Whitish tubular flowers (<2 cm long) with green stripes are followed by smooth-skinned, round, succulent fruits (4-8 mm diameter) from January to March that change from yellow to red and contain numerous seeds.
Are there any similar species?
Native mawhai (Sicyos australis) has prickly, one-seeded fruits. Black bryony (Tamus communis) is also similar.
Why is it weedy?
Grows rapidly, has a scrambling habit and persistent tubers, and can tolerate wet to seasonal drought, warm to cool temperatures, a variety of soils, and semi-shade. Poisonous (not browsed by animals).
How does it spread?
Tuber fragments are spread by water and soil movement. Seed is spread by birds.
What damage does it do?
Smothers low canopy and shrubland, and discourages native seedlings from establishing.
Which habitats is it likely to invade?
Disturbed and open forest and shrubland, and stream edges.
What can I do to get rid of it?
If you suspect that you have found white bryony, do not touch it. This pest plant is under an active national eradication programme, and any attempt to get rid of it could accidentally spread the pest. Any plants found that are suspected to be this species should be reported to Biosecurity New Zealand using the pests-and-diseases hotline on 0800 80 99 66. They will work with you to control the weed.
What can I do to stop it coming back?
Tuber fragments resprout prolifically. Follow up tuber treatment probably necessary for 2-5 years until eliminated.