Mexican bean tree seedlings found near Buderim

Article and images by Stephanie Reif, conservation partnerships officer, Sunshine Coast Council

It’s always interesting to find out what species are coming up naturally in a revegetation plot. Usually its native plants nearby or seeds that have been in the soil seed bank for a number of years waiting for conditions to change. Unfortunately there are also your usual suspects when it comes to weeds in revegetation areas. Well known herbaceous weeds such as blue top and cobbler’s peg through to large woody weeds like camphor laurels and Chinese elm. But very rarely do you get a plant coming up that turns out to be a serious notifiable weed! This is what happened to me earlier in the year on a Land for Wildlife property at Mons near Buderim.

The previous owner had joined Land for Wildlife in 2011 and had used their Land for Wildlife incentive seedlings to revegetate a cleared, grassed paddock, next to a rainforest gully. New owners had since bought the property and asked to join Land for Wildlife. It was during this visit that I took a look at the revegetation and spotted a group of seedlings that looked out of place.

The Mexican bean tree (Cecropia sp) is native to tropical America and is thought to have been imported into Australia probably in the 1980’s. It is a fast growing pioneer tree, usually 10-20m tall. Its stems are hollow and it has large, alternate pawpaw-like leaves. The leaves are green on top, white below and both sides are covered in scabrous hairs making the leaves rough to the touch. Interestingly the Mexican bean tree is dioecious with separate male and female plants.

The male flowers consist of up to 50 spikes to 18cm long and the female flowers are 2-14 yellow spikes up to 30cm long. Their seeds are very small and are in small round but slightly flattened fruits. Flowers are wind-pollinated and seeds are spread by fruit-eating birds and bats. Unfortunately plants quickly mature 3-5 years after germination.

It is thought a plant collector first planted Mexican bean tree at Mission Beach in far north Queensland. It quickly spread liking the warm and wet conditions in disturbed rainforest areas. Its quick spread was noted and it was made a declared plant in 2006 in Queensland, with New South Wales also following suit. It is now listed as a ‘restricted invasive plant’ under the Biosecurity Act 2014 meaning you can’t grow, buy or sell Mexican bean trees.

A number of Mexican bean trees were also deliberately planted in South-east Queensland and Northern New South Wales. Mexican bean trees were identified on the Gold Coast in 2012. These have been removed from parts of the Springbrook Valley including from a number of Land for Wildlife properties. A number have also been removed from Brisbane and one adult tree was removed at Glenview (near Landsborough) a couple of years ago.

So back to the beginning of the story - what happened with the mystery plant at the Land for Wildlife property at Mons? Well it turned out there were 7 seedlings all less than 1m tall in the revegetation area. All were coming up in the one spot, so I took a plant sample from one of these back to the office. It was pressed and sent to the Queensland Herbarium who identified it as Cecropia peltata - one of three Mexican bean tree species thought to occur in Queensland.

I met with Biosecurity Queensland Officer Stacy Harris on the property and she recorded its location and removed the seedlings. Visual surveys have been undertaken of the nearby area from the road and on surrounding Land for Wildlife properties to try to spot the adult trees (since the Mexican bean tree is dioecious there must be a least one male and one female plant somewhere in the area). So far no adult trees have been found.

A media release has been sent out about the Mexican bean tree being found in the Mons area and council is planning on contacting landowners as part of their biosecurity program in spring. If you or anyone you know lives in the Mons, Tanawha or Buderim area and you think you might have Mexican bean tree on your property please contact council on 5475 7272 or Biosecurity Queensland on 13 25 23.

Is it a rice paper plant?

Don’t confuse Mexican bean tree with the rice paper plant, Tetrapanax papyrifer. It has similar looking leaves but they are softly hairy not rough like the Mexican bean tree. Rice paper plant (Tetrapanax papyrifer) is an emerging environmental weed in parts of Australia including South-east Queensland. It is native to Taiwan and eastern Asia and is a large shrub to 4m with numerous small black berries. On the Sunshine Coast it is found in former rainforest areas including the Blackall Range.

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