When does a great Australian timber tree become a pest plant

When does a great Australian timber tree become a pest plant?

When it's growing in the wrong place and causing problems for native plant species.

Meet the Black Bean Tree (also known as castanospermum australe). Norfolk Island has a stand of Black Bean growing in 100 Acre Reserve, planted when the reserve was used an experimental forestry zone. Since that time, the seeds have been collected and propagated for planting in valleys and along creek banks.

This large, bird-attracting tree is an Australian native that reaches a height of up to 10 metres in garden settings and 40 metres in natural rain forest settings. It has clusters of large red, orange and yellow flowers in spring, which give way to large seed pods that each contain between two and six large seeds. Whilst these trees provide shade as they get taller, they're also strong competitors for the sunlight, water and nutrients needed by Norfolk Island native vegetation, effectively removing the foundations for their successful growth.

Black Bean trees also have extensive root systems, which are great for stablising creek and river banks, but not so good - and potentially expensive - if planted within 10 metres of drainage lines, sewers, house foundations, garages or swimming pools.

And while the Australian Aboriginal people know the right way to prepare them as a food source, the seeds are toxic to humans and livestock and can cause severe reactions in people and can be fatal to livestock if eaten.

You can control the spread of Black Beans on Norfolk Island in three ways:

Hand weed young seedlings

Cut and paint stump of mature plants with 1 part Glyphosate to 1.5 parts water

Avoid collecting and propagating seeds