Looking for Mexican bean tree seedlings

Article and images by Rhea Phalan, vector and pest plant officer, Sunshine Coast Council

As we step through the forest we try to navigate between the seedlings, groundcovers and spider webs. We are looking for Mexican bean tree (Cecropia spp.) seedlings that may have spread from the original 2 Mexican bean trees that were found in the Buderim area last year. These trees, like other invasive plants listed on the high priority list in our Sunshine Coast Council local government area biosecurity plan 2017, have not yet become established on the Sunshine Coast. We have to do follow up surveys for several years after finding the initial plants to make sure that they don’t re-establish from dormant seeds. This is one of the best parts of our work as vector and pest plant officers for the Sunshine Coast Council because you get to walk through the forest surveying for specific invasive plants.

As I step down I don’t see any Mexican bean trees but I see seedlings of camphor laurel (Cinnamomum camphora), green cestrum (Cestrum parqui), golden trumpet tree (Tabebuia chrysotricha), African tulip trees (Spathodea campanulata), coffee trees (Coffea spp.), arrow head (Syngonium podophyllum) vine trailing down the embankment and the bright red berries and dark green foliage of coral berry plants (Ardisia crenata). We are on the edge of the forest reserved for native wildlife, natural beauty, and recreation; where a new housing estate's gardens meet the remnant bush. Some of these plants are declared as ‘restricted’ invasive plants under the state government Biosecurity Act 2014 and cannot be sold or distributed, some under our Sunshine Coast Council local government area biosecurity plan 2017 and some are still sold in nurseries. All of them are weeds in this bushland and will have a negative impact on the biodiversity here if they are not managed.

We walk further into the forest and look down, we start to see native raspberry (Rubus rosifolius) and bleeding heart (Homalanthus populifolius) seedlings, native ferns fan out across the forest floor. The bright blue seeds of the native ginger (Alpinia caerulea) stand out beneath the big eucalypts and the dried out leaves of cabbage tree palms (Livistona australis) crunch beneath our feet. The seeds from some of these plants are eaten by birds like the silvereye, Lewin’s honey eater and brown cuckoo dove. The garden weeds haven’t made it this far into the forest yet, only bird dispersed weeds like camphor laurels and coffee trees occasionally pop up. We don’t see any mammals or snakes but we can hear the birds sing and spiders are everywhere. I see a spiny crab spider hanging from a wombat berry vine and leaves glued together by a web form a tunnel into the ground, I wonder who lives in there?

We walk along the small creek that seems to start from within the bushland then up into the denser forest areas. A wait-a-while plant (Calamus muelleri), a climbing palm that birds love to nest in because its spiky stems protect them, pulls at my shirt as I head back up the embankment. No Mexican bean tree seedlings here, so we head back out.

Under our Sunshine Coast Council local government area biosecurity plan 2017 invasive plants are prioritised according to their potential risk to the surrounding environment, which is based on how widespread they currently are, their potential impact and what management options are available to control them. Most of these priority invasive plants listed in the plan can be found on the Sunshine Coast, some more widespread than others. Collectively we have managed to control several of them, stopping them from becoming established. Examples of this collaborative survey and control work, targeting priority invasive plants, include Bitou bush (Chrysanthemoides monilifera subsp. rotundata), Senegal tea (Gymnocoronis spilanthoides), Mexican bean tree, honey locust (Gleditsia triacanthos) and pond apple (Annona glabra). The extent of surveys depends on the dispersal mechanisms and seed dormancy of these plants. For example, it has been six years since the Senegal tea plants were originally found and seedlings are still found every year even though plants haven’t set seed since they were originally found.

You can help protect the biodiversity found on the Sunshine Coast by getting familiar with priority invasive plants under Sunshine Coast Council local government area biosecurity plan 2017 as well as considering the ecosystem impacts when buying new plants for your garden. Getting to know which ecosystems are found in your area and planting native plants that are found in them is one of the best things you can do.