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Historic red cedar propagation success

Ensuring the genetic heritage of our historic trees lives on - the tale of Toona ciliata

Paul Lickorish, Horticulturist, the Royal Botanic Garden, Sydney 

When I first met Fran Jackson, the Manager of the Royal Botanic Garden, Sydney, the first thing she said to me was ‘Do you see that tree over there?’ I squinted into the sun, following the line of her finger. ‘I think so’, I replied, hesitantly. The tree I was looking at appeared bare of leaves, a number of small furry bodies hanging in the naked branches. ‘The flying foxes are destroying some of our most important trees,’ she said, ‘I need you to propagate them’.

Fran reeled off a history of the tree - it was Toona ciliata, the Australian red cedar, planted nearly two hundred years ago by Charles Fraser (first Superintendent of the Botanic Garden) who collected plants from near Parramatta in 1822 and that this tree is probably from that collection. There are no trees left in the Parramatta area; in fact much of the native habitat of Toona ciliata has been cleared. This tree, located within the Palm Grove, has never produced seed, does not sucker, and up until now has resisted all attempts at propagation. I replied, foolishly perhaps but honestly, ‘I don’t believe any plant cannot be propagated’. Fran laughed at that, and looked me in the eye saying ‘I will hold you to that!’

Later on I began to wonder what I had let myself in for. The poor tree was ancient, hanging on to life with the tenacity only old trees know, and there wasn’t a great deal of new growth to work with. Soft-tip cuttings were out, greenwood cuttings would be difficult, but all the older wood was knobbly and hard. Not only that, most of the material was too high to reach easily from the ground. It wasn’t going to be easy.

I went back weekly to scope out the tree; it was dormant until the first week in October when the buds broke and new growth sprang forth. A good year of rain and warm weather had done its work, I needed to act while the new growth was surging hormones down to the roots to restart the process of renewal. I waited a few more days until more leaves had developed, then gathered my pole saw and snuck out of the nursery before my other duties caught up with me and I was lost for the day.
 
After a bit of work, a few of the lower branches were lying on the ground at my feet, and I took them in to the nursery to start work. With my trusty apprentice Joel Cohen we decided to take 10 cm (4 inch) hardwood cuttings using material as straight as possible with some new growth at the tips. The cutting bases were 6-10mm wide and very woody, so we scored them heavily and applied generous amounts of rooting hormone, placed them in to very open cutting mix and put them under the mist.  From this point on it was a waiting game.
 
We waited a few months, I checked the cuttings weekly. Fran came by several times to check for roots and went away with nothing. A few cuttings died, and were removed to prevent rot. Then a few more, we were down to less than half of the original 19 cuttings. The remaining cuttings looked somewhat like the old tree; struggling. It didn’t look good.

Unknown to us, the old magic of rooting hormones and meristematic cells was doing its work under the surface, and after a desultory glance at the bottom of the pot three months later I was stunned to realise that we had been successful! Six of our precious cuttings had taken root, five of which were quite vigorous. They took readily to transplant, and to date, five of these cuttings are growing well under cover on the nursery and we have come one more step forward in discovering how to propagate aging trees.
 
This is one of the success stories of propagation in the Garden - of careful observation and patience. It is still only one success of many ongoing stories of our old trees, and there are many more which need our careful attention. Let’s ensure that the genetic heritage of these historic trees lives on.

Paul and Cedar

potted cedar cutting

cedar cutting

 

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