More thoughts on the development of Potting media

Fred Linton sold his business to Dave at the end of WWII and Dave renamed his business Scotsburn Nurseries.  The development of his secret soil recipe continued with some nasty, chemicals (Methyl Bromide) and then steam pasteurization used to kill off pests & diseases.  Methyl Bromide is just plain dangerous and had to go, it has since been banned.  Steam created issues when it was first introduced.  Until the right combination of temperature and contact time were discovered the results could lead to a mix that was so completely free of micro-organisms that it was quickly re-colonized by the very fungal spores that were not wanted.  This is a key lesson for gardeners, recycled pots and potting mix attached to the roots of plants will carry fungal spores for a long time that can be transferred to new pots and around the garden.  Here’s a tip, Yate’s Anti-Rot is a form of Phosphorus acid that is safe and very effective for controlling the main root rotting fungi, Pythium.


The extended Wood family including Dave, Uncle Maurie, Cousins Claude & Fred and probably a few other nurserymen & florists.

In 1961 Professor Kenneth Baker lectured in Adelaide on the principals from his “UC system for Producing Healthy Container-Grown plants”.  The UC system replaced soil with fine sand and used peat as the organic, water holding component.  Fine sand was relatively cheap as it was “too fine for sand culture, and… because of its low fertility”.  But the low fertility of sand meant that it provided a consistent base material on which to add peat for water holding and an increasingly complex selection of fertilizers for nutrition.  Uncle Robert, his uncle Maurie (Woodlyn Nurseries) cousin Fred Wood (F.G, Wood Nurseryman) and other growers including a young Dick Wall (Wall’s Floriana) headed off to Baker’s lecture and returned with heads swimming with revolutionary ideas like “nursery hygiene” and steam pasteurization.

Production of potting media remained one of the key activities of nurserymen until the 1980’s when some clever science and the business concept of outsourcing caught up with the nursery industry.  Responding to the increasing cost of high quality peat, imported from Europe the DPI Knoxfield (Vic) carried out research to find a replacement.  Sphagnum moss grows in bogs at cold latitudes: northern Europe, Canada and New Zealand.  Over thousands of years layers of dead moss decay and compress producing an extraordinary organic material, peat.  For hundreds of years peat was used as a rather poor fuel for fires in a landscape that did not offer many trees for burning.  Sphagnum moss was also used as a wound dressing because of its exceptional capacity for absorption, the cylindrical structure of the Sphagnum moss cells allows them to absorb up to 20 times their own weight in water and the natural acidity of the Sphagnum helped control infection.  I can’t find when peat was first recognized as a horticultural material but we know the John Innes Institute was promoting it around the turn of the 20^th century.  Sphagnum peat is almost the ideal potting media ingredient, it holds a huge amount of water and balances this with the capacity to trap air and transfer nutrients to roots, it is also relatively nutrient free and if harvested properly it is weed free.  Of course the downside of peat is it is a non-renewable natural resource.  While there are still vast quantities still available for harvest in eastern Europe and Canada, Germany, The Netherlands and Britain have banned further extraction of bog peat.

David’s Beardsell, Nichols & Jones produced a series of papers through the late 70’s & early 80’s that identified Pine (Pinus radiata) bark as a useful substitute.  The key to Pine bark was composting, particularly to remove toxins naturally found in Pine oils.  Well composted Pine Bark has the advantage that the composting process kills unwanted micro-organisms, but retains valuable micro-organisms that drive the composting process.  The living micro-organisms in the composted bark help defend the potting mix from re-infestation by unwanted fungal and bacterial spores.  The enterprising Robert Debernadi of Debco fertilizers saw an opportunity and employed David Nichols as technical consultant and began the development of potting mixes for both the home gardener and commercial horticulture. 

And there is the Revolution.  Scotsburn bought its first load of pre-blended potting mix shortly before I started working here in late 1987.  Despite my nursery industry heritage and training, I have never mixed a potting mix batch.  For consistency, quality and simplicity we fax an order off and expect delivery the next day of a potting media blend that we have tweaked and adapted to suit our plants and environment but not especially different to the mix available in the “Terra Cotta & Tub mix” bags available at good garden centres. 


My cousin Cam, Dave & me.  Yes it's embarrassing and I no longer have that much hair.

I'll finish this little series next week with some thoughts on the future and some practical tips on fertiliser practice.