Plants I love

Chocolate grows on trees

If it’s a birthday there must be chocolate. And so it is that the Story of Chocolate is one of the treats the Royal Botanic Gardens Sydney is sharing for its 200th birthday. The story unfolds in the big present the Gardens recently unwrapped, a new horticultural exhibition space called The Calyx. (For those whose high school biology is shadowy, calyx is not just a handy Scrabble word, but also the term used to describe the cup that protects the developing flower bud. Think of the curving green sepals around a rose bud or the green skirt at the end of a tomato or strawberry.)

The Calyx replaces the Pyramid glasshouse and links with the Ken Woolley-designed Arc glasshouse, completed in 1987. It’s part-exhibition space and part-function centre, its purpose being to fund horticulture as well as to show it off.

Calyx, RBG

Chocolate is a good place to start exploring the deep relationships between money, plants and people. Cacao was currency in Aztec culture and is now traded on the futures market. It grows only in a thin band, 20 degrees either side of the equator, making Hawaii the North Pole of chocolate and tropical Queensland the South Pole.

Calyx, RBG

At the entrance to the Calyx exhibition is a beautifully grown representation of the South American rainforest, featuring rare palms, lots of bromeliads, shawls of Spanish moss, and a mature cacao tree of the ‘Criollo’ variety, which is the one used by the Mayans to make their hot chocolate. Behind the tree is a long living green wall featuring the Mayan god of chocolate as well as the Mayan symbol for chocolate, illustrated in plants. (Interestingly, the images are hard to make out unless you look at a camera screen, which draws the ‘plant pixels’ together.)

Calyx, RBG

The ‘Criollo’ in the Calyx is flowering, with tiny complex blooms springing directly from the trunk, a form of flowering called cauliflory. In the wild little midges like fungus gnats pollinate the flowers but as fungus gnats aren’t welcome in the controlled environment of the glasshouse, Gardens staff are painstakingly hand-pollinating the flowers to see if they can produce a pod before the show closes after Easter next year. In the meantime, freeze-dried cacao pods provided by the Daintree Chocolate Company have been hung on the tree.

The relationship between the midge and cacao is just one reason chocolate responds so poorly to industrialised plantation farming. It’s a plant that grows naturally in the rainforest understorey, with protection from hot sun, and with a thick compost of rotting leaves at its feet providing shelter and food for those pollinating midges and for the mycorrizal fungi that help provide nutrients to the plant. Sustainable farming requires replicating these kinds of conditions, rather than destroying rainforest to establish plantations of high-yield varieties that threaten to narrow the varietal diversity of cacao and send some of its most interesting flavours extinct.

Calyx, RBG

The chocolate-coated conservation message from the opening of the Calyx is that plants are part of an ecosystem deeply impacted by the choices we make. Most visitors seem happy to take the message home – in the form of a block of chocolate from Lindt, which is a major supporter of sustainable cacao in Ghana, and exhibition sponsor.

For how to make chocolate once you have grown the cacao, check out this on Melanie Boudar’s chocolate plantation tour in Maui.

It’s time to

Watch pines
A new pine nematode is killing pine trees in the Sydney basin. Plant Biosecurity NSW is asking for help reporting dead and dying pines so that the nematode and its vector beetle can be tracked. Go to

Cut back
Trim liriope to the ground to allow fresh new growth to rejuvenate the plant.

Feed bulbs
Use a soluble fertiliser on spring bulbs you plant to keep for next year.

Buy fragrance
Daphne is one of the signature scents of winter. ‘Perfume Princess’ is a new variety that flowers over a long period, with an intense perfume, in gardens or pots, semi-shade or full sun. It’s Australia’s Nursery and Garden Industry Plant of the Year for 2016.






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