Where land has been extensively modified or polluted by humans, some weed species grow in areas native plants won't. Many are capable of absorbing pollutants and nutrient run-off, increasing soil organic matter and building topsoil, making the land habitable again for desired species. Environment Southland states that cadmium in New Zealand soil has increased after many years of farmers fertilising with cadmium-rich superphosphate. It points out that Hort Research has named willow as a species with the ability to decontaminate soils polluted with cadmium.
Weeds are also used in herbal tinctures. Some, such as cleavers (biddibid), are recognised as important medicinal herbs. My dog happily chomps on this plant when he finds it. Try making cleavers tea as a purifying tonic. It also makes a good face wash, tightening the skin. Do your research first with all home herbal remedies: avoid consuming cleavers if you are on blood-thinning medication.
No dig for healthy soil
A no-dig method to improve soil structure involves chopping or hoeing weeds (before they seed), leaving them on the soil to break down. Add tree mulch on top as a carbon source. The worms and other soil life will incorporate this material back into the soil, and they'll appreciate being fed. The weeds are nitrogenous, and will add nutrients to give your soil an energy boost. Over time, you'll have lovely friable topsoil.
Brew your own fertiliser
Yellow-flowering Kahili ginger is one of those desirable garden plants gone AWOL. Once it sniffed freedom it ran for the hills, taking over native bush habitat. But Kahili, like most weeds, can be used to make rich liquid fertiliser by rotting the chopped-up plant and root in a barrel of rainwater. Tradescantia can be tied up in a black bag and left in a hot spot where it will eventually turn into rich compost. Weedfree Trust sells a large weed bag called The Black Hole, along with blue ginger barrels. Both are perfect for turning weeds into useful fertiliser. See weedfree.org.nz
Food for thought
Fire your imagination and give chickweed, finely chopped onion weed or onion weed flowers and spicy nasturtium flowers a go in your next salad. I made a pasta dish the other night and mixed in Waiheke Herbs' Herb Spread, which features nasturtium, dandelion, plantain, New Zealand spinach and calendula in the ingredients. Delicious. To find out about edible weeds in New Zealand, plus great recipes, see juliasedibleweeds.com
Artist warms up to the charms and diversity of 100 weeds
My designer friend Jacinda Torrance set herself a 100-day challenge.
Each day she illustrates a different weed with fine brush and ink:
"I have chosen to draw weeds ... because of the huge variety of plant forms that are easily available to me.
"No one minds if I extract one from the edge of their garden or verge. I am forming a love-hate relationship with these plants as I get to know them. It is fascinating to discover that many are useful, even edible.
"At the same time the invasive nature of many of the climbers is alarming to observe."
I love Jacinda's delicate filigree drawings. They are beautiful, unique artwork.
She is getting to know the weeds she is illustrating and can rattle off their benefits.
When I dropped in we shared a pot of delicious dandelion root coffee.
• See her work in 100 Days Project: Inkweed
