Spinifex

It is so incredibly well designed for what it does.

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What is it and what does it do? It’s the seed head, the seed-carrying part, of a type of dune grass called spinifex, and it goes rolling and spinning its way down the beach, carrying the seeds of the spinifex plant to other locations. On windy days, you can see scores of these seed heads scurrying their way down the beach, and only when the seed head becomes adequately lodged against something, and submerged in sand, will the actual seeds be released, and hopefully, new plants will grow.

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Spinifex on beach

They don’t know where they’re going, or why—but that’s what they do.

I like how spinifex looks. It looks like some Tinkertoy thing, which would roll in all directions, that I used to make years ago as a small boy. Or the prototype for some futuristic space vehicle—perhaps something that could land on planets and roll around exploring their surfaces.

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If you look closely, the spinifex legs are flexible. They are wispy and don’t dig in. They touch down and allow the seed head to be propelled forward with even the slightest of breezes. And no matter how it lands, it’s always on its feet. It all seems so clever and just plain smart.

The particular species of spinifex (Spinifex sericeus) found in New Zealand—it’s also found in Australia*—is the North Island’s most important dune, sand-binding grass. Spinifex grows long tentacle-type roots that claw and spread, holding sand together, and consequently helps sand dunes to form and protects beaches from erosion. Indeed, protecting, preserving and encouraging the growth of spinifex is a major part of dune restoration and protection in New Zealand.

The seed heads themselves can be up to 30 cm (12 inches) in diameter but most are smaller. The plant itself tolerates high winds, salt spray, shifting sands—an environment that most of plants shun.

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Clumps of spinifex

 

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Spinifex dune grass – protecting the dunes.

Plants use various strategies to spread their seeds. The hope is to disperse the seeds in as wide a range as possible around the host plant. Or another way of saying this is that plant species that employ such strategies, or have grown to evolve such strategies, are the ones that have survived.

Perhaps the most basic form of seed dispersal is gravity. The seed, often enclosed in a fruit, simply falls to the ground. Seed breaks lose. Falls to ground. That’s it.

Many plants, similar to spinifex, use wind-blown tactics to spread their seeds. When the seeds mature on the plant, they somehow make use of wind or air currents to spread farther than they would otherwise.

Think of tufts of seeds on dandelions or the winged seeds on maples that flutter down like tiny helicopters.

Other plants use water for their seed-dispersal strategy. Some seeds float and are carried to new locations. This includes even such large seeds as the coconut.

One of the more dramatic methods of seed dispersal is termed the ballistic method. Seed pods ripen and dry and then “detonate,” essentially erupting open and spitting seeds in all directions. Some types of these seeds are also then carried by the wind.

Finally, plants have evolved seed dispersal strategies that involve animals. Some seeds are in the form of burrs. They get caught and tangled in animal’s fur or feathers and carried to new locations. Some animals, such as squirrels, bury seeds, which they then forget about. Perhaps the most common method of seed dispersal enlisting animals is for the animals to eat the fruit enclosing the seeds. The seeds, due to protective coatings, then pass unchanged through the digestive tract of the animals and are deposited in the animal’s droppings.

It’s little things like spinifex seed heads that make nature so endlessly fascinating. At least a few others agree with me—last year here in Tauranga, a huge metal sculpture, nine meters high, was erected in tribute to the lowly spinifex seed head.

 

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Spinifex sculpture, Te Puke, New Zealand (1)

 

*Confusingly, spinifex is also used as a common name referring to another different, spiny-leaved grass common in the outback of Australia.

 

All photos by the author except as noted.

1)Tauranga Eastern Link project update – March 2015
‪www.tepuke.co.nz‪389 × 194‪Search by image

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