Oddly named hawthorn in a pond

Flashback to November 2022. After a day of driving past hawthorn hedges such as these, flowering white and occasionally pink, the Australian Garden History Society pre-conference tour group to northern Tasmania visited a garden with its aquatic namesake, the Water Hawthorn. We were at Connorville, the home of Roderic and Kate O'Connor, a marino farm just off the east of the Central Plateau in Tasmania. 

There were plenty of terrestrial plants to enjoy but I didn't recognise this distinctive white-flowered, floating aquatic. Stuart Reed suggested Water Hawthorn, and he was right (as he often is). It's Aponogeton distachyos. Also known as Cape Hawthorn, Cape Pond Weed or Cape Asparagus. Or in Victoria, Cape Pond-lily, where it has become established in natural areas after escaping from ponds and irrigation channels such as these.

Clearly from the common names, it's from the Cape, in South Africa, but well established (and weedy) in North America, Europe, Australia and New Zealand. The 'Hawthorn' component of at least two common names is curious. Perhaps the white flowers from a distance reminded someone of a hawthorn bush or hedge?

In South Africa, where also known as Waterblommetjie, the flowers and buds are added with the potatoes in the final stage of a mutton stew, creating a 'local delicacy'. I gather the young shoots and roots can also be eaten. 

As you can see the oval leaves float on the water surface, looking a bit like the native Swamp Lily, Ottelia ovalifolia.

But the chunky flowering stalk is quite different, emerging in winter and spring, the perfect time for a hearty stew. That white structure is a collection of flowers, with the flowers themselves a bit obscure in these pictures. You can see the anther-bearing stamens on this close up at least.

The white teeth-like structures, in two rows, are sometimes called bracts but in VicFlora we consider them 'perianth' (a general term for sepals and petals), with one 'tooth' per flower.  

The flowers are sweetly perfumed - like vanilla it's said - but I didn't get any hint of that in the middle or a rather hot November day for Tasmania. I spend most of time in the shade of a nearby Hawthorn hedge, continuing to mull over the borrowing of this common name for an entirely different looking plant.