Targeting weeds at ground level
IT’S hard to believe that among the most successful of all weed- suppressing plants, potatoes remain one of the most effective. I’m already starting to harvest some tasty, early- planted tubers, but those that went in late during November have produced so much foliage it’s no longer possible to see between the rows.
Weeds – even the most aggressive species – have little chance of competing for light against this dense and wonderfully productive ground cover.
The few straggly weeds that manage to break through are easily pulled out and if seed heads have not formed, they can simply be laid flat on the ground to harmlessly rot.
Pumpkin plants, once established and growing fast, are another highly effective way of not only smothering parasitic plants, but like potatoes are a marvellous way to clean up a weed- infested vegetable bed.
The most frustrating of weeds in Tasmanian gardens is rope- twitch. These plants spread and survive by sending out long, root- like stolons, each with a sharp point.
This weed is also called couch- grass because its stolons send out fine, hairlike anchoring roots at intervals, similar to traditional couch- stitching. This makes it very difficult to remove from heavy soil.
While it can be contained by regular cultivation or by heavy mulching, twitch can also be smothered by using more dominant plants. Among the most effective is the common forget- me- not. The dense mat of leaves stems and soft blue flowers cover the ground, robbing the twitch- grass of light.
The weed eventually becomes so weakened by this competition it can be easily pulled from the ground, stolons virtually intact. And after a few months, the loose- rooted forget- me- nots can easily be cleared away.
African marigolds ( Tagetes erecta) especially the tall, vigorous varieties such as Crackerjack, have a devastating effect on all grass weeds, including twitch. These highly attractive marigolds have large, double- yellow flowers and produce a special root chemical. This not only stops most adjacent grasses from growing, it eventually kills them.
Seedlings can be bought by the punnet at most garden centres, while packets of cheap seed are available for immediate sowing. It pays to keep removing twitch- grass during the early stages of growth, but luckily, African marigolds grow very fast.
Another easily grown ornamental weedsuppressor is the yellow- flowered Californian poppy. This too can be highly aggressive and will spread widely, almost like a weed.
However, the plants are so loosely attached to the soil they can easily be raked out – roots and all – after they have done the job.
For more permanent solutions to persistent weeds, especially on exposed, dry banks, there are several tough but beautiful perennials that are able to compete very successfully.
Among my own favourite is the oldfashioned gazania.
They too are available as seedlings from good garden centres. The plants will rapidly colonise large areas of ground, especially if regularly divided to create new plants. The most common gazania produces orange blooms, but there are lots of cultivars that produce yellow, red, pale pink or wine- coloured daisies. All gazania plants love full sun and are marvellously drought- resistant.
Densely foliaged, dome- shaped shrubs such as hydrangeas, or Mock Orange ( Philadelphus) can also be used as highly attractive weed controllers.
Many other shrubs, including a beautiful range of ground- hugging junipers, have long been used for easy- care gardens and public landscaping.
However, most are relatively slow- growing so it is necessary to prepare the ground carefully before planting. That means digging out most weed roots and destroying weed seedlings until the ground- covering shrubs have grown large enough to capture the light and dominate the ground.