Meet Australia's citrus gurus: the trolleys from Renmark

Clive Blazey discovers a garden where citrus, dates, mangoes, peaches and apples thrive.

Meet Australia's citrus gurus: the trolleys from Renmark

About 30 years ago when Ian Tolley was just 57, I travelled to Renmark on the Murray specifically to talk to David Ruston about roses and Ian about offering citrus trees to our club members.

Both today are internationally regarded world leaders in their fields, a very rare but well deserved recognition of their service to Australian horticulture.

Intriguingly, both went to the same school where they shared a classroom and have lived their lives less than one mile from each other.

Many Diggers members know Ian through his Masterclasses where he translates an extraordinary knowledge by his showmanship into infectious enthusiasm for gardening, with sessions often lasting 2-3 hours. He is also an agricultural consultant, an author, an expert on irrigation and nursery practices, and he maintains a citrus arboretum where he specialises with his wife, Noelle, in the production of seed for citrus rootstocks. Both have been honoured; Ian an OAM and Noelle an AM.

Recently I visited Ian again for the purpose of establishing an arboretum of citrus cultivars (like the one pictured below) at Heronswood.

We intend to establish a collection of all the best Australian climate adaptations resulting from the mutations that have occurred following 200 years of exposure to our intense ultra-violet light.

We can now, through the Tolley's pioneering work, find heirloom citrus cultivars that perform better in our climate than the original imports of Lisbon lemons, Florida grapefruits or Mediterranean sweet oranges.

Our discussions go on for 10 hours and we have only covered a fraction of the subject’s depth.

Sandy soils of the Sunraysia and Riverland are so poor

The sandy soils in which all our horticultural crops of grapes, citrus, almonds, olives, avocados and soft fruits are growing in the Mildura and Renmark areas, are so poor that all the soil provides is good drainage and root anchorage.

Their successful adaptation is simply because of the number of units of heat, the access to irrigation from the Murray and the availability of artificial nutrients supplied through added fertilisers. In short the soil is so poor production is entirely based on artificial input, i.e. it is horticulture rather than gardening which usually assumes growth from naturally fertile soils.

It is remarkable how lush, green and fertile these plantations are compared with the drab, dry and arid natural vegetation that is evident whether you drive or fly into this desert landscape.


The Trolley's Garden

With abundant watering and skilful selection of fruit trees it was astounding to find how self-sufficient their garden is. Imagine picking from four mature avocado trees 1,500 fruit of either the Reed, Haas, Bacon or Gwen varieties, 45 kilos of dates or 300 Kensington Pride mangoes!

They also have 11 different table grapes as well as persimmons, peaches, nectarines and surprise, surprise even Fuji apples. Their garden is now like an oasis with gigantic specimens of figs, Washingtonia palms, lemon scented gums and the beautiful rainforest trees of Agathus robusta which are at least 20 metres high.

Their climate is rapidly heating

When Ian was a school boy he suffered from chilblains when heavy frosts would last till 11am but not today. Instead of the 30 days a year of frost, which would cause severe damage to most trees, now with climate change he has to adjust to much longer periods of excessive heat.

Last year Renmark had 11 days over 42°C with a peak of 47.5°C. This excessive heat affects fruit set on citrus, apricots and peaches and causes erratic fruiting on avocados and mangoes because at 47°C all fruitlets drop off the trees.

Building a fertile soil over 70 years 

Their infertile soils have improved after 70 years of gardening and watering. They now have 6-12 inches of top soil by mulching and by using Zeolite and transferring biota from nearby fruiting trees (by scooping one inch of top soil and spreading to their trees to ensure beneficial mycorrhizae advance the nutrient uptake).

Ian's Books

There is so much knowledge in Ian’s head that all citrus growers, both commercial and at home, can benefit from.

Ian has recently updated his book Citrus: A Gardener's Guide, first published in 1999 with Bruce Morphett.

It is a masterpiece of information with monthly fruiting charts, weekly water requirements and basic help about choosing varieties and their compatible rootstocks.

But there is an even greater volume to come with Ian now in the final stages of a record of his lifetime’s work on citrus and there are examples everywhere of where his knowledge could be applied.

As we drive around the orchards we see lots of failures particularly by orchardists growing Imperial mandarins on incompatible rootstocks, which in less than 10 years strangle the uptake of nutrients leading to their premature death.

This tragedy reinforces the importance of matching soils climate, rootstocks and cultivars carefully and how much we rely on his skills to grow Australia's most popular fruit trees.

He explains how long lived citrus trees are, with some 800-year-old specimens still going strong, so to lose a whole orchard in less than 20 years is a tragedy of ignorance.

After all we have just transplanted 20 year old trees into our Heronswood vegetable garden so easily they look like they were there all the time. But how much longer can we call upon Ian Tolley's expertise? So we eagerly await his 300 page magnum opus on citrus which is due later this year.