Why we love weeds....
[Posted Spring 2018 in the Kikuyu Margin Project, which was later replaced by separate Projects for each section of Gahnia Grove's kikuyu margin, so this post was moved here.]
It's often hard to explain why we love weeds - while doing everything we can to get rid of the most threatening ones.
As the commonest, most rapidly produced plant material on a site, they are the first available source of Food for Plants - once rotted down, they form humus, nutritious and, more importantly, breaking up the clay to allow roots and water to penetrate. Without enough humus, plants suffer more from both drought and flooding, and can't absorb enough nutrients. The dense clay typical of Kaipatiki is rich in nutrients, but without organic material in the soil, plants can't absorb them.
The same goes for water. Rotted or dried plant material incorporated into the soil creates micro-channels for water, allowing it to reach plant roots - and reducing the amount that washes downhill, making paths slippery, causing erosion and polluting the streams and seas with sediment.
Diversification and protection of native vegetation are the planned outcome for these previously-sprayed and trimmed margins of the mown kikuyu lawns. The native trees likely to arise spontaneously on this ridge will be wind-hardy and acid-tolerant, and unless the soil is rehabilitated will need to be drought-tolerant if they are to survive.
Weed-suppression will be by manual selection, uprooting or spot-mulching depending on the nature of the weed and the availability of mulch.
Spot-mulching is usually easier and more effective than uprooting. It also improves soil moisture and health, shading the ground and creating the humus that feeds subsequent plants.
It is our intention to avoid the introduction of materials from other sites, for disease-control and cost-reduction.
Therefore we depend on the mulch available on site - preferably from close at hand. As long as weeds are being abundantly produced, we have an excellent source of mulch for weed-control, moisture-retention and plant food.
Generally the first source of plant material for the rehabilitation of the soil along the edge of mown kikuyu is the kikuyu itself, as it continues to spread from the mown area.
Grass-growing season is here, and it's time to define the area of unmown, untrimmed kikuyu that, through manual pull-back, will generate the essential mulch to control its own regrowth from its clone-patch, while rehabilitating the soil.
It will look different to the customary short-back-and-sides.
It will have height.
It will grow in diffferent directions - rumpled, backwards, and sideways - instead of to a neatly trimmed edge, or smoothly downhill into the native planting. More and more, it will be growing upside-down, showing only the browned undersides of long leafy stolons. These unruly clumps of wiry stolons probably won't die till winter, when, now rearranged to inhibit growth, they will rot in the cold wet weather...leaving a small amount of loose loamy topsoil for next year's seedlings.
It will, increasingly, hold familiar weeds of pasture - docks, initially, then sow-thistles, wild carrot, Parsley dropwort, Ox-tongues, Scarlet pimpernel, vetch, Cleavers, Red deadnettle, Common and Purple-top Vervains, Prunella, Lesser swinecress, chickweeds, the native (and locally wild) Esler's weed, the often-present but seldom recognised native Nahui and Microlaena stipoides, and...the as yet unknown, to be identified, selectively eradicated, reduced, suppressed or nurtured as required - till, among these ground-breakers, emerge the kanuka, manuka, karamu, totara, mingimingi, the unknown contents of the present seedbank, and the products of wind and birds.
So bring on the weedy growth of summer along Gahnia Grove's borders, watch it grow up and diversify and be pulled out and trampled and mulched, wonder and wait and look for surprises.
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We managed to get by without the docks, having plenty of more benign exotic herbs such as wild carrot, Verbena spp, Bristly oxtongue etc, which we used to shade and crowd out those dock seedlings not mulched or uprooted.
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