What to do with an underperforming plant?

The small leaf bluebush is a native shrub with huge potential for habitat restoration projects. It can colonise damaged ecosytems, stock can graze on it, and it provides groundcover for small birds, reptiles and insects. But it’s notoriously bad at germinating when collected and planted in new locations. We decided to investigate.

In natural conditions Maireana brevifolia, or the small leaf bluebush as it’s commonly known, is a successful pioneer species – one that’s adapted to colonise disrupted or damaged habitats. It also recovers well from grazing and once present will spread naturally.

But time and again attempts to collect and re-plant the seed have resulted in little or no seeds germinating. This indicates that the seeds might have a high rate of dormancy – a natural state where seeds are prevented from germinating even under environmental conditions normally favourable for germination.

With its high potential for our landscape restoration projects we wanted to know why the seeds rarely germinate. So we sponsored an honours project with Curtin University in Western Australia to investigate the “Seed Viability and the Effect of Various Seed Pre-Treatments on the Germination of Maireana brevifolia”.

In other words we wanted to find out if the seeds had a high rate of dormancy. And if they did, what could be done to break the dormancy and make them grow.

Tiffany Bennett, a University of Western Australia graduate in Botany, decided to take on the honours project and commenced work in April 2012. We’d like to say a big thanks to Tiffany who proved to be a diligent and dedicated researcher and completed the project on time.

Now let’s start with the bad news.

None of the three common seed treatments that Tiffany tested – oven drying, cool storage and gibberellic acid – had a significant effect on germination rates. Some even had a negative impact on early seedling growth. The results showed that no quick-fix is offered by the treatments.

The good news is that the research revealed that there’s actually little or no dormancy in small leaf bluebush seeds, and the majority of viable seeds will germinate immediately after rain.

The study also investigated seed viability percentage and showed that 54% of seed was viable. This aspect of the research was supported by our partners at the West Australian Kings Park research facility where seeds were x-rayed under the instruction of Dr David Merritt. This x-ray analysis is an efficient and non-destructive method of assessing seed quality which can reveal details of seed embryo development and insect infestation.

The results still leave us with a couple of mysteries that need further investigation:

Why aren’t the remaining 46% of seeds developing to maturity?

Why have attempts to collect and re-plant the seed been so ineffective when there’s little or no dormancy and 54% of the seeds are viable? There are some theories out there. Insect attack, particularly from red legged earth mites, could be causing problems. Seed handling and storage might also need modifying to increase germination rates.

But although there’s more work needed the results will prove to be invaluable for our direct seeding program. We’re definitely a step closer to accessing the full potential of a perplexing plant.

Following on from her work with Greening Australia Tiffany was selected as a finalist in the Young Professionals in Agriculture sponsored by the Agricultural Institute of Australia.

You can also find her full study published in the December 2014 edition of the AG Institute Journal.

Seed collection

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