When will my native plants flower?

· Guest post by Julia Hazel ·

Short answer: hard to predict. Long answer: please read on…

Expect natural variation

Native plants at CDTLI’s nursery are grown from locally-collected seed to maintain the natural characteristics of each species, including natural variability between individual plants.

This variation between individuals is essential for native species to survive in the wild. It’s also valuable in revegetation planting and can be good for gardens too. But it means we cannot expect our native plants to behave like commercially cultivated species. Those have been selected, over many seed-generations, for predictable growth in human-regulated farms and gardens.

The planting guide said…

Flowering periods mentioned in books and web pages usually indicate ‘typical’ or ‘average’ timing for a species if it’s growing in the area(s) known to the authors. Even if you are in the same area, each of your plants will be influenced, sometimes in unpredictable ways, by very localised variations in soil, climate and weather.

Hibiscus townsvillensis
Photo: Julia Hazel
Give them time

Small, short-lived species will typically flower during their first year. Slower-growing shrubs and trees are likely to need a few years of growth before their first flowering. Then they may start with rather sparse flowers and take a few more years to reach peak flowering.

Can we help them flower sooner?

To some extent, yes. Do some research first, and choose each plant to suit the particular spot you have for it. Some species like part shade but many of our native plants flower best with lots of sun. Take care, however, at the planting stage: tiny plants may need temporary shade.

Get your new native plants off to a good start. Early progress will help them flower sooner. Ensure they get regular water and a little native plant fertiliser at first. Transition to less frequent watering as the plant gets established, and allow it to adapt gradually to natural conditions. For some species, flowering is triggered by the onset of rain after a prolonged dry period.

Pavetta australiensis
Photo: Julia Hazel

Another tip: don’t prune unnecessarily. More branches and leaves help the plant take in extra energy for growth and flowering. Also consider where on your plant the future flowers will appear. If you cut back a species that produces its flowers at the ends of the branches, the plant must grow new branches before it can flower.

For many species, flowering is influenced by natural changes in day length, temperature and dry season/wet season moisture levels – but the interaction between all those factors is complex and hard to predict. Some people like to intervene, for example giving copious water at certain times, and it can be fun to experiment.

It’s often easier to let your established native plants do their own thing. Most likely they will give you a some nice flowering surprises over time.

Grevillea parallela
Photo: Julia Hazel

Leucaena leucocephala: friend and foe

· Guest post by Dave Pratchett ·

Goondaloo Creek Landcare site became the focus of my Landcare volunteering in 2019, soon after we moved to Townsville. Assisting with weed control and watering in the newly planted section opposite Tech NQ, I could look upstream to an area rejuvenated through years of sustained effort. But downstream was dominated by leucaena trees, heavy with seed pods. From a local Landcare perspective, these trees are a major foe.  

I cannot help but feel partly responsible for the invasion by this particular weed species, because early in my career in Australia, I worked hard to grow it!

The establishment of leucaena as a cattle fodder in Australia was led by Dr Ray Jones and is a fascinating story. The plant contains toxic mimosine and Ray proved that ruminants can tolerate this only when they have a very specific gut bacterium; he identified the bacterium (which was then named Synergistes jonesii) and by sheer persistence, brought samples to Australia.     https://csiropedia.csiro.au/leucaena-toxicity-solution/

In the 1980s I worked with Ray running trials in the Ord River Irrigation area to determine the optimal stocking rate and plant density for finishing cattle bred on Kimberley stations. Although various problems reduced marketing potential, the value of leucaena as a fodder crop was proven spectacularly as we reached 1500 kg (5 head) per hectare. https://researchlibrary.agric.wa.gov.au/cgi/viewcontent.cgi?article=3401&context=journal_agriculture4

I noted “Leucaena seedlings are difficult to establish under dryland conditions and under irrigation. Germination and emergence are usually not a problem, provided the seed is treated with hot water to break dormancy. Once the seedlings are two to three centimetres high, growth slows down and weeds can compete with and smother them’.

No one has boiled the seeds of the leucaena plants which have now invaded much of Northern Australia and they establish particularly well along river banks, and in cleared areas. The species is however a useful fodder plant cultivated by cattle producers in parts of Queensland, including our local area. It is also a ‘friend’ to many in  its native South America and countries such as Indonesia and India, where leucaena is a valuable dryland fodder and has an amazing variety of other uses, including human nutrition. http://archive.unu.edu/unupress/food/8F163e/8F163E08.htm

So, like all weeds, leucaena is a problem only when it invades areas where it is not wanted. It is certainly not wanted on our Landcare sites and I look forward to spending my later years in Australia working with Coastal Dry Tropics Landcare volunteers to reduce the damage it has caused here.

Birdwings and butterfly vines

· Guest post by Malcolm Tattersall ·

Many of us know that we should grow a particular vine to attract Birdwing butterflies to our gardens but just what the vine is called, and which butterflies rely on it, are recurring questions.

Very briefly, the caterpillars of one group of Swallowtail butterflies feed exclusively on one group of closely-related plants. The butterflies are the Troidini, a “tribe” (in scientific language that’s a level between “family” and “genus”) of Swallowtails (Papilionidae) and the plants are the Birthworts (Aristolochiaceae).

Our Troidini are the Clearwing Swallowtail (Cressida cressida), Red-bodied Swallowtail (Pachliopta polydorus) and all of the Birdwings (Ornithoptera species). The Aristolochiaceae we’re interested in are in the genus Aristolochia, or used to be. Many of them are commonly known as Dutchman’s Pipe vines.

Everything gets messy at the next level of detail. If you want to avoid that but still attract the butterflies to your garden, this is all you need to know:

  • Aristolochia acuminata, also known as Aristolochia tagala, is a food plant of all our Birdwing species and of the Red-bodied and Clearwing Swallowtails, and it is the vine most widely grown in Townsville gardens. It is sold by the Bush Garden Nursery as Aristolochia acuminata.
  • Richmond Butterfly Vine, Pararistolochia praevenosa, is a food plant of all Birdwing species and the Red-bodied Swallowtail. It is the vine widely promoted in SE Queensland as the “birdwing butterfly vine.”
  • Dutchman’s Pipe Vine, Aristolochia elegans also known as Aristolochia littoralis, is the main one to avoid. It’s an exotic, introduced from South America, and it poisons our butterflies. The adults lay their eggs on it but the caterpillars rarely survive.
  • If you stick to the Latin names, there should be no confusion about which vine is which.‬

One reason that the questions never seem to go away is that there have been changes in the scientific names of both the vines and the butterflies. Another is that “common names” (the names in English) are used inconsistently to cover several similar species. And, finally, there are several other native vines which are food plants for one swallowtail butterfly or another. All of these are discussed in the longer original version of this article on my blog “Green Path”.

How the “coronavirus tree” got its name

· Guest post by Adam Goulding ·

Before COVID-19 caused temporary closure of CDTLI’s Bush Garden Nursery, our Saturday sessions were often busy and tended to attract passing walkers, cyclists and runners. We even had a couple come in half way through our volunteers’ smoko, only to be rather disappointed that we were not a coffee shop, as they originally thought.

On our last open Saturday, we had four running types who were interested in native plants. One of them had a picture of a tree for me to identify. So, gingerly maintaining my 1.5 metre social distancing, I looked at their photograph.

It showed the round flower head of what they called the “coronavirus tree” . And yes, it indeed looks similar to a greatly-magnified coronavirus!

I was able to identify the tree species and pointed to one of these trees growing at the Nursery. As botanical readers may already have guessed, it is the Leichhardt Tree, Nauclea orientalis.

To me henceforth Nauclea orientalis will be referred to as the “coronavirus tree”. I will be planting one of them in my garden to remember the global pandemic.

The image accompanying this post is “Australia’s ‘coronavirus tree’ ” created by Julia Hazel as a derivative of “Nauclea orientalis” by Tony Rodd (used under CC-BY-SA) and “Computer render of SARS-CoV-2 virus” by the US Centers for Disease Control and Prevention (in the public domain). It is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Native plant identification resources

· Guest post by Tim Doolan ·

Tipping my hat to the present COVID-19 restrictions (not that my hat gets much wear now) I hope everyone is enjoying their meditation on solitude. What better time to discover some new resources for native plant identification!

Apart from asking someone who knows better, or going straight to Google, I’ve always wondered where your average punter goes for species information. When I was just starting out in the space it wasn’t easy to find resources on the subject, so this article is one of those ‘services to a past version of myself’ type of things.

Over the years I’ve found myself coming back to the same resources over and over, so I thought it might be worth listing my favourite three. This is by no means a definitive list. A lot of the Landcare crew are associated with JCU or happen to have botanical encyclopedias inside their heads. But for us mere mortals the following resources might be useful to know what you’re looking at.

  1. Field Guide to Plants of the Dry Tropics – Keith Townsend (available from Mary Who Bookshop)
Field guide book cover

Best bits: Visuals are top rate making identification easy.

Since it’s a small field guide, it’s not full of a huge amount of information. For example, I like to know as much as possible about natural habitat so I can make deductions about other things. But that said, what is provided is excellently condensed into a single paragraph for each particular species and really is fit for purpose for a small manual like this one.

  1. Across the top: Gardening with Australian plants in the tropics – Keith Townsend (available from Mary Who Bookshop)
Across the top book cover

Best bits: Considerable species compilation. Also, the first 50 pages or so are a decent and rare summary of common gardening issues in Townsville.

This book provides bare bones information. The sporadic visuals mean it’s not the most useful layman field manual.

  1. Australian Tropical Rainforest Plants at this website

Best bits: Extensive resource for Australian tropical rainforest plants. Both scientific and lay identification information with useful visuals and other interesting tidbits and trivia.

Note that the focus is on ‘tropical rainforest plants’ and misses a lot of the dryland ‘Brownsville’ species.

  1. Honourable mention – even bigger plant nerds than me

Quite often there are people at CDTLI, James Cook Uni, Society for Growing Native Plants, etc that can tell you things you won’t find written down anywhere. It’s just the nature of the thing that there is too much out there to be able to catalogue, so we all have our gems of knowledge. Which is why I suppose we like the adventure of it all so much.

Best bits: wealth of information sometimes documented nowhere else but inside their brains.

Note not as easy to access as a book from a library or a website

Bottlebrush or paperbark? Callistemon or Melaleuca?

· Guest post by Malcolm Tattersall ·

This all began with a somewhat puzzling comment in the gardening column of our local newspaper, “The Tinaroo Bottlebrush (Melaleuca recurva but still sold as Callistemon recurvis) is…”

“Isn’t a Melaleuca a paperbark?” I wondered. A bit of digging (no, not in the garden) showed me that what I thought I knew wasn’t true any more.

We have two kinds of names for plants, common names and scientific (Latin) names, and in this case both are problematic.

Scientific names

Scientific names are more precise than common names but they are sometimes changed by the taxonomists, and any changes take time to percolate through to the rest of the scientific community and the general public. In this case we had two closely related groups of plants long classified in two genera, Callistemon and Melaleuca, recently merged under a single name. Callistemon [species name] therefore became Melaleuca [species name] overnight.

The rationale for the merger is explained in this excellent article on the Australian Native Plants Society (Australia) website:

…the problem with the current classification on the basis of the arrangement of the stamens is that this supposed difference is not clear cut and Callistemon tends to merge into Melaleuca rather than being unambiguously distinct. The well known Callistemon viminalis is one that has often been discussed as not easily fitting the accepted definition of Callistemon. …A paper by Lyn Craven of the Australian National Herbarium (Novon 16 468-475; December 2006 “New Combinations in Melaleuca for Australian Species of Callistemon (Myrtaceae)”) argues that the differences between the two genera are insufficient to warrant them being retained separately and that they should be combined. As Melaleuca has precedence, adoption of Craven’s work would transfer all species of Callistemon into Melaleuca. Some state herbaria have adopted this change but, at this stage [2018], the re-classification has not been taken up in the Australian Plant Census, which ANPSA recognises as the authority on plant nomenclature. While all Callistemons have their flowers arranged in a “bottlebrush” shape the inflorescences of Melaleuca may also have a globular or irregular shape. It should also be remembered that there are other genera in the myrtle family which may have free or united stamens combined with “bottlebrush” flowers. Botany was never meant to be easy!

So the debate began more than ten years ago and the result is still not universally accepted. The Bush Garden Nursery, however, has made the change: you won’t find a Callistemon on the stocklist. One last little wrinkle is that the form of the species name must match that of the genus, which is why Callistemon recurvis became Melaleuca recurva rather than M. recurvis.

Common names

Paperbarks are named for their bark and bottlebrushes for their flowers. Given that some bottlebrushes have papery bark and some paperbarks have bottlebrushy flowers (sorry, but it’s hard to be more serious), the separation of their common names must always have been blurred. In fact, one particular tree in our own garden  worried me for years on just this account.

We have two small trees which are unambiguously bottlebrushes, one huge tree which is unambiguously a paperbark, and a tall but very scrawny tree with loose flaky bark (photo below) and red bottlebrushy flowers (pictured above).

Image of flaky bark

Should we call it a paperbark or a bottlebrush? We can call it whichever we like, since common names are like that. Is it a Melaleuca or Callistemon? Well, it’s now a Melaleuca, whatever it used to be.

My Friendly Local Expert put my mind at rest when I asked, informing me that it’s the rare red-flowering form of the common Melaleuca viridiflora, so it has always been a paperbark and a Melaleuca. I should have asked long ago!

Just for the sake of completeness

  • Banksias also have bottlebrush-shaped flower spikes but are distinctive enough not to be easily confused with Melaleucas.
  • Grevilleas are more closely related to Banksias than to Melaleucas but some have flowers which might mislead the casual onlooker. The common name of large species is “Silky Oak” but most species are known by the Latin name.
  • In some ways Hakeas forms a link between Grevilleas and Banksias, having hard woody seed pods with Banksia-like seeds while the flowers occur in Grevillea-like clusters.
  • Leptospermums are in the same family as Melaleucas (Myrtaceaeand share their common name, “Tea Tree” (also spelt “ti-tree”), with paperbarks.

This article first appeared on Green Path, Malcolm’s wildlife and environment blog, in 2018.

Lorikeet with Black Beans

· Guest post by Malcolm Tattersall ·

No, this isn’t a recipe.

The Black Bean in my title is a local tree, Castanospermum australe, and you wouldn’t want to cook with its seeds because they are too too big and too toxic. Two of our neighbours in Mundingburra have well-grown specimens and I am simply taking this opportunity to share an October photo of its attractive flowers.

I know the tree as a local species but didn’t realise just how limited its range was until I looked it up: a patchy distribution along our tropical coast, and that’s all. Nor did I realise just how high it can grow – forty metres. (I wonder if our neighbours know, but I’m not going to tell them in case they start worrying and get their trees chopped down. We need all the trees we can get, and these are very beautiful.)

Black Bean timber is both beautiful and rot-resistant. The latter quality has seen it used for fenceposts, but that seems a terrible waste when it makes such attractive furniture.

According to the Australian National Herbarium, “it is native to coastal rainforests and beaches in Australia from around Lismore, New South Wales to the Iron Range, Cape York Peninsula, on the Queensland coast and 160 km west to the Bunya Mountains. It grows in moist, fertile, well-drained soils on terraces on the side of mountains or along the banks of rivers and streams.” It also grows in many Townsville primary school grounds, where the heavy seed pods tempt children into mischief.

The importance of local provenance native plants

· Guest post by Christine Dalliston·

Local Provenance is the term used to describe native plant populations that naturally occur in a given area.

Many native plant species can be found to occur naturally across a broad geographic area or range. For example, Hairpin banksia (Banksia spinulosa) naturally occurs across 3 states, from coastal Victoria to Cairns.

However, the plants growing in a specific area will have adapted to the local conditions over a long period of time. Although of the same species, a Hairpin banksia from southern Victoria will have a different genetic makeup to its cousin in Cairns, just as the same species of plant found on the coast will be different from that growing in the mountains. Different populations containing local genetic variations are called provenances.

For true local provenance, the individual plant is grown from seed stock from parent plants within the same population (or as close by as possible).

Bringing in plants sourced from a different region can compromise the genetic integrity of the species i.e. weaken the ability of the plant population to thrive in the specific local conditions through diluting the genes that have been selected over a long period of adaptation to local conditions. Eventually, given time and the right conditions of isolation, this variation between populations can lead to new species evolving.

Preserving local provenance populations, on the other hand, is an important way of protecting biodiversity and combating the threat to biodiversity posed by climate change.

Aquatic weeds in the Ross River

Sagittaria/Delta Arrowhead (Sagittaria platyphylla) is a recent arrival to the Ross River, first found here in 2012. It is currently under a containment program in attempt to eradicate it from the river before it spreads throughout the region. Sagittaria is a highly invasive aquatic weed that can choke shallow waterways, including irrigation channels, blocking the flow of water, fish movement and recreational activities. The economic impact of Sagittaria is imense with farmers in the Murray-Darling basin collectively spending over $2 million on control each year to protect and restore irrigation channels.

Water Hyacinth (Eichhornia crassipes) Water hyacinth is a floating weed that forms a dense mat on the top of water bodies. It has light purple flowers and round, dark green leaves. Water hyacinth was originally introduced from Brazil to Australia as an ornamental pond plant. The dense floating mat restricts wildlife migration, depletes the oxygen levels of the water body and interferes with recreational use.

Cabomba/Fanwort (Cabomba caroliniana) grows completely underwater (except flowers) in slow moving or still water, forming a dense canopy below the surface of the water. The stems can grow to a massive 10m long and pose risk to swimmers who can become entangled.

Water Lettuce (Pistia stratiotes) is a floating water weed with spongy, fan-shaped leaves. It can form dense mats of material that shades out other plant species. Reproduction is by seed or runners which produce daughter plants. Water Lettuce has a rapid growth rate and if conditions are favourable it can quickly spread to cover an entire water body once introduced. The seed is generally spread between water bodies by water movement, natural or within water vessels or equipment.

Hymenachne (Hymenachne amplexicaulis) is a grass with long, wide leaf blades found in shallow water or the banks of rivers and can grow to 2.5 m high. Hymenachne forms dense stands and can increase the possibility of flooding by restricting water flow in drainage channels. The dense stands also pose risk to animals by restricting migration and reducing available habitat.

Salvinia (Salvinia molesta) is a free-floating, spongy water weed, found in slow moving water bodies with high temperature and nutrient loads. Salvinia impacts waterways by removing available habitat, shading the water column and reducing water quality by removing dissolved oxygen. Leaves are small and folded with tiny hairs on the surface and roots float freely in the water column. Salvinia does not produce flowers and therefore the only method of spread is believed to be transportation of live material between water bodies.