We were sitting in the winter sun in his garden when I idly asked a keen vegetable-growing friend what his soil was like.
Mary Lovell-Smith gets down to earth to look at the wonders of soil
He shrugged his shoulders. “Dunno,” he replied. “Heavy? Sandy?” I suggested. He remained uninterested. “Wouldn’t have the faintest. As long as it grows good vegetables, does it matter?”
There’s a bit of wilful ignorance going on here, a lack of curiosity and a missed opportunity to develop a deeper connection with his environment.
For soil is particular to its site, offering gardeners a close sense of place and time. It is a major factor they have to contend with regularly when they garden, be it planting, weeding, watering, or simply working out why one plant is thriving and another not. A site’s soil contains a whole geological history.
So when I mutter to myself about mine, about how bone hard it is to dig into in summer and how sticky and dank it is in winter, reflecting on its origins eases the pain a little.
My garden is on the lava flow of an ancient volcano.
Its centre was near the middle of Lyttelton Harbour (the port of Lyttelton sits inside the crater). The soil is heavy clay, positively puggy in places; in other parts there is literally no soil, just bedrock. And here and there in between, there is something resembling a friable loam.
The volcano first came to life about 20 million years ago and carried on for 14 million years, spewing out basalt and other igneous rocks, which over a few more million years were covered with a mantel of loess. These fine particles of greywacke were carried by the winds to Banks Peninsula from the Southern Alps and are easily recognised in the yellow clay banks all over the peninsula.
Then came the overlay of colluvial soil, eroded from the bedrock. Next – and much much later – came the thin layer of topsoil built up from vegetation and tiny organisms.
Of course, the layers are not as clearcut as this all sounds, with colluvial and loess mixing with each other and with the various periods of volcanic activity.
Christchurch poet Dennis Glover in his 1970s poem Pigeon Bay summed up the soil profile beautifully: “Over the hard lava. A khaki clay balaclava And a thin shirt of dirt.”
I have learnt to live with the khaki clay balaclava.
I don’t dig into it unless planting a tree or shrub for it is rock-hard when dry and sticky when wet. For beds, I pile on top of the clay as much organic matter as I can muster, such as pea straw as well as composted horse and cow manure. I disturb the clay as little as possible. I have tried gypsum to “break it down”, heaps of it, but the verdict is out on its efficacy. I struggle to grow lemons and no longer even try with rhododendrons but take solace in how beautifully my roses bloom and my fruit trees produce.
My shirt of dirt is indeed thin in places, non-existent where the bones of “hard lava” poke through. These I try to appreciate for what they are: a semblance of “normal“soil and a design feature.
To be fair, my friend lives in a small back section in the upmarket Christchurch suburb of Merivale.
Maybe it is harder to identify or have any sense of turangawaewae on a patch of dirt with no other determining natural physical characteristics.
Soil for him is the sweet-smelling and rich compost he makes himself for the raised beds in which he grows his veges. Soil is the medium in which his wife grows ornamentals in the rest of the garden, and to where he reluctantly relinquishes the remainder of his compost.
Very likely he knows the geological history of Christchurch and the plains upon which it stands, but I doubt he feels it deep in his bones, and maybe won’t till he immerses his hands in the soil.
Which of course, he won’t. That’s what his wife and the gardener are for! ✤