I grew up with the idea that weeds were a problem. And, on an orchard farm, they can be. November was always the month when the ground was still too wet to slash, but there was enough warmth and water for the weeds to reach up to two metres in height. Mostly the wild radish flowers, which are quite pretty, but still. It’s a fire risk, and firebreaks always had to be done by December 1st if not earlier. Plus, avocado trees have a shallow root system so you really don’t want a lot of weeds competing with them for nutrients, especially when the trees are nutrient challenged thanks to Phytophora attack. I grew up with glyphosate spraying under our trees as a standard tactic, and weeding in the vegie garden as a standard job. It just wasn’t something you thought about.
This started to change one time when I visited my dad on a uni break. He sent me out to weed the upper part of the vegie garden, which was loam soil with a lot of clay in it. It was a bright and warm sunny day. Most of the weeds were Portulaca, a hot-season succulent weed that lies flat in spreading mats on the ground. I noticed as I was weeding that where the Portulaca hadn’t grown the bare soil was drying hard and impenetrable in the sun, and the tiny amaranth seedlings we were hoping to encourage were just poddling along without really thriving. Everywhere I pulled out the Portulaca the soil was moist and crumbly underneath, and full of worms, bugs and other little life. I was starting to feel uneasy over weeding when Dad called lunchtime. So we went in, had a cuppa and sandwich, came back out – and in the area I’d just weeded was a big, long, fat tiger snake, curled up and enjoying the sun. As most Australians know, tiger snakes are in the top ten venomous snakes of the world – or is it the top five? – but they’re lovely and sweet creatures as long as you DON’T DISTURB them. So that was the end of weeding for the day. It got me thinking though about why the snake would have come to lie on the soil. The more spiritual aspect of life says that Nature protects its own and if you don’t listen to its tiny voice within you, it sends louder and louder messages until you get it (a tiger snake being the equivalent of shouting “You IDIOT!”). The more scientific aspect of life looks at the warmth of the drying soil, the developing moisture penetration barrier and the barren areas trapping and holding better heat for a reptile needing to sunbake. Having to stop weeding meant I got a chance to talk to Dad about both of those. And regardless of which reason meant more, we agreed that maybe we should leave the Portulaca in place.
I spent a bit of time reading about weeds along the way. Mainly because I’m fascinated by plants, all plants, and because many of our weeds turned out to have a fascinating history as well as being quite edible (though not necessarily eatable, an important distinction). Every so often in my plant research I’d come across a note about some property a particular weed had, a way it affected the soil, and I’d make a mental note. The info was scattered throughout many books (much of this was before the Internet) but that’s OK, my memory was good at filing that sort of trivia. Among those factlets was a comment about the weeds from the Asteraceae – the ones with dandelion-like flowers that turn into puffballs – both needing high potassium levels, and acting as potassium concentrators. I came across that when reading about fertilising crops with treated humanure or sewage sludge. There’d just been a side comment somewhere that using urine could mean an increase in the ratio of potassium in the soil, and these plants helped bring that balance back down by trapping the potassium in their tissues. It got filed in the mental stack somewhere.
And then, I got asked by a friend of a friend to come help sort out her garden. She’d been away overseas for five months and the garden had weeds up to her eyeballs. Literally, she was a short woman. And, it turned out, the weeds were mostly Asteraceae. Which I didn’t think much of, until she explained that she was using treated blackwater on her garden – she had one of the systems that takes all your wastewater and puts it through worms and bacteria and soil filters and suchlike til it’s suitable for a garden, then automatically sprays it onto the garden when it’s ready. She was rousing up to a big rant about the laziness of the guy who was supposed to have kept an eye on the garden for her, when I pointed out that the weeds were doing her an enormous favour. In the time she’d been away, they’d put the soil back into a better nutrient balance, and I showed her as I pulled the weeds out how their deep root systems had helped keep the laterite-clay-rock-based soil from hardening up and drying out without her regular care. She’d returned to freshly conditioned garden soil which only needed the weeds pulled to be ready for planting. Having those weeds there for a few months had saved her a lot of work and digging on her return.
I’ve been very conscious of weeds since, because I’ve found over and over again that the plants which grow in an area are both the ones that like those exact local conditions, but which also remediate the conditions to some degree. For instance if the soil’s hard, you get more of the weeds with strong taproots that can punch through it – but once they’ve punched through, other things can grow. When I arrived at the house where I currently live, there was little sign of weeds. The previous tenants had cleaned up immaculately before leaving, as per contract, and everything was mown to the ground. It didn’t take long though before I found compass weed growing only in the area where a dead bush had been mulched and left insitu a few years before, or couch grass invading thickly an area which had once been mulched bed and then stopping where the soil changed, or oxalis marking out the areas that remained shaded and moist first and longest. Instead of constantly weeding and mowing the large block I found myself on, I used the weeds that grew in my first winter to help plan where and what I’d plant. They told me far more about the soil history and local conditions than I could have got from asking previous occupants.
So far in my new gardens I’ve mostly used weeds for information and let the gardens do their own thing while I slowly work through them – but there are a few places where I’ve used them for soil remediation. There’s an area out the front under the neighbour’s mulberry tree where I’m starting a dichondra bed. Last autumn I reconditioned the soil there seeing as it probably provides a third of the mulberry tree’s nutrients and we certainly enjoyed having the berries. I used some kaolin clay my brother had given me to help increase the water retention of the soil – but kaolin does have this terrible tendency to clump, forming pockets and hard layers. Especially if you just dig it in fast with a shovel. I knew I might be inadvertently forming a barrier to absorbing moisture rather than increasing the soil’s ability to hold water, and I crossed my fingers. This winter and firstspring it’s been easy to see where I inadvertently spread the clay less evenly. The areas with more of it are densely packed with sows’ ear, wild chrysanthemum and other Asteraceae. I let them grow as long as I could, but now the dichondra needs more light and space in order to establish fully before summer. As I’ve pulled them, I can see that their penetrating roots have broken up those clay pockets and turned them into beautifully blended soil. Where I pull up the grassy weeds, I find the clay pockets still separated and breaking away in lumps from the compost, leaf humus and sand.
The other place where I’ve deliberately chosen a plant to become a weed is under the lemon tree. I’ve been selecting plants I want to grow there as weeds over last winter and this, and have had one success so far: nasturtiums. The branches immediately above last year’s two nasturtium plants grew more lemons than the other branches, all bigger and fatter too. This year I managed to get nasturtiums growing all the way around the tree – but they chose to only grow at the drip line. Which is fine by me. One of the reasons for choosing nasturtiums is they cover a lot of ground, protecting its moisture absorption and retention, but they don’t choke out the root space. And citrus trees have their active roots around the dripline. So those nasturtiums have picked the spot best for them – but it’s the spot that will best ensure a good crop of lemons next year.