The weeds of spring

A field of  mouse-eared chickweed and wild aster. Both species thrive when the competition has been killed previously.

A field of mouse-eared chickweed and wild aster. Both species thrive when the competition has been killed previously.

One of the ongoing problems in the wetlands is weeds. Because the soil is so fertile and moist, come the warm weather and we tend to be inundated by them. At present there are far more species of weeds than native plants, after all, not only were the wetlands left vacant for many decades, but there were several irrigated vegetable gardens there too, for such plants as alfalfa and carrots. And lets not forget that there were a few years in which the wetlands was used to house a small herd of Shetland ponies. One way to deal with weeds is broad-scale spraying with glyphosate in the form of bioactive Roundup or other appropriate herbicides.

Bill is of our volunteers who makes it his regular job to spot weed in small or difficult places, unsuited for broad-scale spraying.

Bill is of our volunteers who makes it his regular job to spot weed in small or difficult places, unsuited for broad-scale spraying.

While we try to minimise the application of herbicides, with 30 acres of land that contains a massive seed bed and with occasional floods that readily deposit even more, hand weeding is not an option in most places. That doesn’t mean we don’t try. Where our planted species occur, weeds readily grow, even through the thickest mulch. In these cases we use mattoacks and a range of weeding tools to physically remove the weeds and replace the mulch. As time goes on we know that many of our plants will provide root or shade competition to discourage new weeds from occurring. But in these early stages it is a weed’s paradise, after all weeds love disturbance best, and that is what we are up to at the moment. Where broad-scale weeding won’t work, we spot-spray in tight niches or where a few targeted weeds occur in relative isolation. One of our FROGS’ members has modified existing equipment to minimise wind drift and makes it his job to routinely and sequentially walk the wetlands, removing such culprits.

Greg mulches the inter-tussock spaces. Even mulch is no permanent guarantee against thriving weeds.

Greg mulches the inter-tussock spaces. Even mulch is no permanent guarantee against thriving weeds.

So what are our main weeds? There are too many to list in this space. Almost certainly worst is Chilean Needlegrass, This is a relative newcomer, having arrived in Goulburn around the early 2000s. It didn’t take long to establish itself in moist valleys and riversides. Soon a plant that many took to be the healthiest looking speargrass they ever saw covered thousands of acres, aggressively excluding most other plants in its path. The good news? Well, it is palatable to cattle and only has a relatively short seed life of about 3 years. The bad news is that it is incredibly invasive. In the wetlands we sowed several hectares to native grasses at great expense. The native grasses came up, but, despite having slashed, mowed and sprayed twice, so did Chilean Needlegrass and it was so vigorous it completely swallowed up the native grasses, only a tiny fraction which has been seen since. The other serious problem with needlegrass is that it sets seed in three parts of the plant: the seed head (well, you’d expect that), inside the stalk holding up the seedhead and, worse still, at the very base of the tussock. In other words, mowing has little or no effect on the spread of this species. The golf course beside us is largely mown needlegrass.

Burr-medic in flower. Great thickets growi in the moist soil above the water-line.

Burr-medic in flower. Great thickets growi in the moist soil above the water-line.

Below are some photos of typical weeds found during spring in the wetlands.