Plants I love

Why are banksia flowers so big?

Why are banksia flowers so big? I’ve long admired those huge cones, run my hands over their almost-plastic perfection, marvelled at their fabulous geometry and great colour combinations, but I’d never considered the question until I read Tim Low’s Where Song Began.

Banksia serrata

Bankisa serrata and friend, photographed on the walk south from Merry Beach to on the south coast of NSW.

As Low explains it, banksia (and other Australian flowers) are big as a result of a kind of evolutionary arms race with Australian honey-eating birds and mammals. In a land of abundant sunshine and impoverished soils, plants photosynthesise like crazy but don’t have the nutrients to turn that energy into growth. Instead they produce nectar, lots of it. With an abundant food source, the birds grew bigger (and more aggressive and much louder), and to survive their weight, the flowers needed to toughen up or collapse. The banksias, which can produce nectar for up to 20 days, are the biggest and toughest of the lot.

Matchstick banskia, Banksia cuneata

This is the matchstick banksia, B. cuneata, one of the rare beauties in the Collins collection.

There are 79 species of banksia in the world and Kevin and Cathy Collins have all of them growing in their garden, The Banksia Farm, at Mount Barker in south-west Western Australia. The Collins’ is the only full collection in the world. They no longer open the garden on a regular basis but banksia fans can stay in the B & B on the property and book a walk around the garden with Kevin.

Kevin Collins

Why does Kevin remind of a character out of May Gibbs?

A full set of banksias would be an impossible act to replicate in Sydney as the majority are native to the sandy soils and low humidity of Western Australia and less than perfect drainage spells death. But local gardeners can grow our local banksias. Banksia integrifolia, known as coastal banksia, is the least fussy about soil and has green-yellow flowers through autumn, with a silvery sheen to the candles when they first form. B. serrata, old-man banksia, has saw-toothed leaves and a develops a fabulously gnarly trunk. It is perfect in sandy coastal conditions, must have good drainage, and can be pruned to keep it to an appropriate size, or to emphasise its sculptural form.

Banksia serrata

So much to love in a banksia flower – the colours, the texture, the geometry. This one B. serrata.

Our local banksias are also good for pots. The dwarf forms of Banksia spinulosa are the easiest to find, and to grow. ‘Birthday Candles’ grows to about 50cm high and has yellow flowers with red styles through autumn and winter. The original plant material for ‘Birthday Candles’ came from Schnapper Point near Ulladulla on the south coast. ‘Stumpy Gold’ was developed from plant material collected at Catherine Hill Bay on the central coast. It has noticeably greyer foliage than ‘Birthday Candles’ with and gold on gold flowers.

Feed banksias in the garden or in pots in spring and autumn with a low-phosphorus fertiliser developed for native plants. Kevin Collins advises that banksias love a good mulch, kept clear of the trunks. Trim off the spent flower heads in spring and that’s all the maintenance required.

These dwarf banksia candles bloom into winter, providing a feast for birds. And when the big wattlebirds land for a breakfast feed those resilient and spectacular flowers barely waver.

It’s time to:

Bag a book
The Foundation and Friends Annual Book Sale is on Friday May 27, 11am -4pm and Saturday May 28, 9.30am – 4pm, Joseph Maiden Theatre, Royal Botanic Gardens, Sydney.

Choose citrus
‘Clementine’ mandarins, unlike most mandarins, can hang on the tree for months without deteriorating. Perfect for home gardeners.

Plant poppies
Plant seedlings close together in a sunny, fertile spot. Fertilise prodigiously for flowers all through winter.

Plant bulbs
Spring bulbs can go into the ground or into pots now, though tulips are best left in the crisper for another few weeks. Sow seed or plant seedlings of annuals at the same time to take over once the bulbs fade.

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