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The big chill in my alternative food garden

An alternative winter food garden.

We have a Rare Fruit Specialist who works in the nursery on Saturdays. His name is Dennis and here are a few snaps of his winter garden following on from the previous winter, spring, summer and autumn blogs.

It is amazing what you can grow successfully in a suburban garden in Melbourne despite the hot and dry weather we have most summers due to normal relatively mild winters. However this winter it was a real doozzie of cold nights and frosts in last two weeks of June here for me something I had never experienced in over 10 years. The lowest recorded outdoor temperature was -2.7 c one morning in my garden which was the lowest I had ever seen. As you know from previous blogs I am a keen grower of the sub-tropical and exotic fruits so expected there to be some damage but there were also some pleasant surprises of survival too!

The effects clearly seen on soft leafed sub-tropicals with totally scorched leaves – tamarillos, babacos, black sapote (leaves and stems really black now) and three year old passion fruit wilted (gone). The tamarillo fruits were okay and all the fruit have ripened, babaco fruits should ripen in November and both are sprouting new leaves again. My ‘Podded’ and covered sub-tropicals – avocados, curry leaf tree and mango (surprisingly) show no or minor ill effects, the acerola cherry defoliated (looks okay) and three year old coffee blackened and gone (flowered last summer and had beans but takes no frost at all).  No terrible effect on citrus, cherimoya (cold climate custard apple), feijoas, jaboticabas, macadamias (flowers okay) and white sapote (despite leaves frozen solid).

Tamarillo with leaves totally burnt by frost.

Three year old Passion fruit vine may be dead.

Three year old Coffee totally blackened may be dead.

Jaboticaba showing reddening of leaves due to cold stress.

It is not all bad as there may be a plus side with great winter chill for all my pip and stone fruit and interspecific hybrid apricot / plum / nectarines?  So what is winter chill in basic and very simplistic terms? It is the number of hours below 7 c measured during the three main winter months of June, July and August required to set off flowering and blooming in many fruit trees. But it is not quite so simple as many factors affect chill units including the specific variety and whether a tree is in the sun or shade, wind etc. Then there are also other models that deduct from the chill units if the temperature rises above a certain level.

So here is a list of winter chill hours for some of the more common fruit trees that could be grown in Melbourne and I would like to highlight some.

 Almond 500-600

Apple 400-1000 (Low chill varieties are less)

Apricot 500-600

Japanese Pear 400-500

Blackberry 200-500

Blueberry (Northern High Bush – Deciduous) 800

Blueberry (Southern Low Bush – Evergreen) 300

Chestnut 400-500

Cherry 700-800

Citrus 0

Currant 800-1000

European Pear 600-800

European plum 800-900

Fig 100-200

Filbert 800

Gooseberry 800-1000

Grape 100+

Japanese Plum 300-500

Kiwi 600-800

Mulberry 400

Peach 600-800

Persimmon 200-400

Plum Cot 400

Pomegranate 100-200

Quince 300-500

Strawberry 200-300

Raspberries 700-800

Walnut 600-700

Apples have a wide range chilling requirement hours depending on the variety 400 to 1000 so choose the variety carefully. 

 Japanese Pears require only 400 – 500 while European Pears are 600 – 800 and therefore flower much earlier.

Japanese Plums require only 300 – 500 while European Plums are 800 – 900 and therefore flower earlier too.

There are a range of low-chill fruits like citrus, figs, mulberries and persimmons that do well in Melbourne.

 Some of the high-chill fruits like currants, European plum, European pear and even raspberries maybe more difficult in the bay side suburbs but would be fine in more inland and hill suburbs so careful selection may be required.

Josephine pear will it ever flower ???

If you are having trouble with getting good blossoming on your fruit trees then the lack of winter chill hours for your specific variety may be an issue and some years may be better than others. I have some five year old dwarf European pears of ’Josephine’ and ‘Beurre Hardy’ that have developed flower spurs but never actually open flowers in spring yet so I will be interested to see if the cold winter has helped. I have a five year old ‘family’ apple tree with five ‘Heritage’ varieties grafted on but one never blooms although it has fat flower buds in winter and they just turn into leaves!!

Apple tree with five varieties showing fat flower buds.

 I guess in conclusion a cold winter is great if you are trying to grow some of the high chill requirement deciduous fruit trees but a problem if you are trying to grow some of the tender evergreen sub-tropical and more exotic plants from warmer climates

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