Perfect Tasmanian Blue Gum for inner city garden

School's back, and it seems I have more to say about plants. Talking Plants returns, albeit now fortnightly rather than weekly. 

In other news, during my sabbatical I announced my resignation as Director and Executive of Royal Botanic Gardens Victoria, effective July 2023. Still six months in the best job in the world, and plenty of opportunities to post before and after then on plants and gardens. 

Now, back to (almost) normal transition with a selection of stories from that Great Southern State, Tasmania...

When someone mentions the Tasmanian Blue Gum, we think of a towering tree like the ones above (to 90 metres in some Tasmanian forests), with long lanceolate leaves hanging from limbs often draped with shredded bark. 

Perhaps also some of that distinctive glaucous blue juvenile-foliage if the tree is damaged in some way or there are seedlings nearby.

I also think of terrace houses in Melbourne, in the 1970s, courageously (aka stupidly) planting a young sapling in their tiny front yard.

Yet there is a variant - an 'ecotype' - these inner-city folk could have planted with more foresight. These are multi-stemmed ('mallee') forms reaching only 4 metres or so where they grow on exposed granite headlands in eastern Tasmania (a similar form also grows at Wilsons Promotory in Victoria).

At Cape Tourville, where I photographed the tree above (and those following), the 'dwarf form' (as it is called) grows within 300 metres of the typical forest form of the same species. Mostly it has been assumed the reduced habit of the cliff top specimens was due to exposure to salt, wind and/or water stress.

However, when seeds were grown in a simple garden experiment, it turns there was some genetic basis to that height differential. A later study using DNA comparison showed that each isolated population of clifftop plants had its own origin (that is, they didn't all have a common, short ancestor) and were not interbreeding any more with their nearby forest relatives. 

The question I have, though, is why isn't this variant available to grow in our home gardens. It may be that the genetics only constrain the species so far, and away from the coast you might get a slower growing but still rather large eucalypt at your front door.

Another reason might be that the Tasmanian Blue Gum is not the prettiest or most interesting mallee. If you want a small eucalypt, there are plenty of better ones with showier flowers and more interesting fruits. 

If you have your heart set on a Tasmanian Blue Gum, perhaps you are better off buying a house on a larger block somewhere in the outer suburbs or beyond. Or better still, moving to Cape Tourville.


you guys really know your plants.