“The fairest thing in nature a flower still has its roots in earth and manure”

Iwas down in Dunedin last week and while there I went to see my good friend, NZ Gardener columnist Margaret Barker at Larnach Castle. I have visited her extraordinary garden several times, but while poking about it on this trip, I came upon the remains of an outdoor building I had not noticed before. This outhouse was apparently the Larnach family’s outdoor dunny and the excrement collected therein was mixed with horse manure to produce methane gas, which was piped in to the house to power the lighting.

I was rather tickled by this piece of Victorian ingenuity although it is probably still only my second favourite example of the clever use of poo in the garden. For me, it is hard to top the pineapple forcing pits I saw at the Lost Gardens of Heligan, in Cornwall, where the 19th century gardeners would grow pineapples in deep trenches surrounded by a mix of horse manure and straw that was regularly soaked with horse urine. The fermenting manure released heat which created the tropical conditions which allowed the pineapples to bear fruit (fun fact: after the pineapple pit was restored in 2010, the gardeners at Heligan actually grew a pineapple using the Victorian method. It took more than 30 tonnes of manure and they worked out that, if you calculated the cost of labour and resources required, the fruit would have to sell for about $20,000 each).

It is a truth universally acknowledged that gardeners love poo. And no wonder. It’s widely and constantly available, and makes a marvellous soil conditioner as the organic matter it contains breaks down, and adds humus to the soil which in turn increases its ability to store nutrients and water. Yes, you need to age it before using it – uncomposted manure can burn plant roots and often contains viable weed seeds – but that just takes a little time (and time, like manure, is free).

Hipsters and hippies might wax lyrical about the permaculture design principle known as ‘energy cycling’, but they are hardly the first to see that organic matter should never be wasted. Way back in 250BC, the Greek botanist Theophrastus was singing the praises of “dung waters” and advising the gardeners of the ancient world to use the heat from fermenting animal waste to warm the soil to speed up the ripening of crops. About a hundred years later, Cato the Elder wrote about the many uses of dung, suggesting composting it or soaking it in water to make a liquid fertiliser (fun fact: Cato was also the very first person to write about using worms in your compost system).

There’s archeological evidence that Stone Age farmers in Scotland were using manure to improve their soil and increase their harvests as far back as 12,000 years ago (apparently they would just plough over an old midden). There’s a written description of making compost with animal manure on a set of clay tablets carved during the Akkadian Dynasty some 10,000 years ago. (Or so I’m told, and I have to take it on trust. My Akkadian is pretty rusty).

Those old gardeners recognised not all manure was created equal too. In The Gardener’s Labyrinth, published in 1577, Thomas Hill rated dove dung as best, “for it possesseth a mightie hoteness”; followed by “hen and other foules“, followed by the dung of an ass, “for his leisurely eating, digesteth easier, and causeth the better dung”; followed by goats, cows and finally pigs. I mean what useful sensible advice that is. I’d hire Thomas Hill as a writer for NZ

Gardener today if he was still alive, and his spelling was better. Have a great July in the garden everyone!