GAR­DEN­ING Does nut­grass drive you nutty?

No stop­ping this ve­ra­cious weed known the world over HOW CAN I GET RID OF NUT­GRASS?

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With TAFE Queens­land South West hor­ti­cul­ture teacher Paul Luck An­swer: Nut­grass, or Cype­rus ro­tun­das, is a prob­lem weed all over the world. In the USA it’s known as pur­ple nut sedge, in South Africa it’s win­tjiek­weed or red grass, teki in In­done­sia or motha in In­dia. From an­cient times, rhi­zomes and tu­bers of this weed have long been used as a herbal rem­edy to treat bowel and stom­ach dis­or­ders in sev­eral coun­tries in­clud­ing China, In­dia, Iran and Ja­pan. As you can see, we are not the only ones deal­ing with this lit­tle green shoot and it’s ac­tu­ally com­monly re­ferred to as the “world’s worst weed”!

There is no ques­tion that nut­grass is a very per­sis­tent pest for the gar­dener and land­scaper, and it doesn’t end there! I have seen nut­grass shoot through thick as­phalt and pool lin­ers; there just seems to be no stop­ping this pest.

It has been shown that nut­grass can re­main dor­mant or in­ac­tive in soil for up to 10 years. The nuts that lay below the sur­face in soils will shoot af­ter be­ing dis­turbed by move­ment. Any­thing that shifts and cracks the earth al­low­ing wa­ter and oxy­gen deeper into the soil may ac­ti­vate the dor­mant nuts. For ex­am­ple, I de­mol­ished a con­crete slab un­der an old Queens­lan­der a num­ber of years ago and had nut­grass grow­ing within a week.

Nut­grass grows best in full sun­light when ad­e­quate nu­tri­ents are avail­able. It gets out of con­trol when al­lowed to grow with­out com­pe­ti­tion from other plants, but only com­petes well in per­fect grow­ing con­di­tions. It is for this rea­son that in­fes­ta­tions are of­ten no­ticed for the first time when we spend a lit­tle time in our gar­dens. Fluff­ing up, cul­ti­vat­ing or im­prov­ing the soil, im­port­ing soil, fer­til­is­ing, weed­ing, re­mov­ing old plants and heavy wa­ter­ing are all ac­tiv­i­ties that can dis­turb nuts and en­cour­age them to shoot.

Glyphosate is the com­mon in­gre­di­ent in many store-bought her­bi­cides and is of­ten mar­keted as Roundup or path weeder which you can use to fight this weed. Glyphosate is a non-se­lec­tive her­bi­cide and will kill any plant that it con­tacts, so be very care­ful what you spray. It is re­ferred to as a translo­ca­tion killer of weeds and will travel through the nut­grass into the nuts and kill the whole plant. You will re­quire a num­ber of treat­ments.

For sit­u­a­tions like in the home lawn where you need to avoid killing your grass, look for a chem­i­cal with the ac­tive con­stituent halo­sul­furon-methyl. This chem­i­cal is com­monly sold as Sem­pra.

Sem­pra in­hibits a key en­zyme in the plant’s meta­bolic path­way and stops plant growth. Plant death oc­curs 14 to 21 days af­ter ini­tial ap­pli­ca­tion. Un­like glyphosate, halo­sul­furon-methyl does not translo­cate through­out the at­tached tu­bers, so mul­ti­ple ap­pli­ca­tions may be re­quired if the in­fes­ta­tion is par­tic­u­larly ad­vanced. In some cases, a one-off treat­ment is suf­fi­cient.

In my opin­ion, chem­i­cal con­trol is the most ef­fec­tive way of rid­ding your gar­dens of nut­grass.

Hand pulling nor­mally only causes the weed to send out more nuts. Read the chem­i­cal in­struc­tions for best re­sults.

Happy gar­den­ing!

Dis­claimer: The com­ments pro­vided in this ar­ti­cle are gen­eral in na­ture only and are not a sub­sti­tute for pro­fes­sional ad­vice. The au­thor ac­cepts no re­spon­si­bil­ity for any ac­tion taken by a reader in re­la­tion to this ar­ti­cle.

PHOTO: IAN READ

WEED: Nut­grass is a most in­va­sive weed, hav­ing a world­wide dis­tri­bu­tion in trop­i­cal and tem­per­ate re­gions.

PHOTO: CONTRIBUTED

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