Tar­get­ing weeds at ground level

Sunday Tasmanian - Tassie Living - - HOME - Peter Cun­dall

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.

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