Weed Control

Weeds in lawns, you are going to get them at some time doesn’t matter how well you look after your lawn, they can get into your lawn by air movement, bird droppings, and mower contamination or even of shoes.

Controlling weeds in lawns is a real specialise field, we aim to be as environmentally friendly as me can with our chemical applications.

Each and every grass species has different requirements in regards to weed control, what might work for one species of grass won’t work for another that is why it is important from day one to get the correct advice on lawn installation.

Of all grasses couch has now become one of the easiest grasses to keep clean from weeds and undesirable grasses.

Lists of chemicals that control following: –
  • Katana – Couch Lawns only
  • Sempra – Nutgrass control in most grasses
  • Expo 500 – Poa control in cool season grasses
  • Puma S – Summer grass control in cool season grasses

Cape Daisy

Cape Daisy (Arctotheca calendula) is also known as Cape Weed. As depicted in the photograph above, it has short thick horizontal stems with a rosette forming at the ends of these stems. As a result it forms thick, dense patches in lawns. The upper side of the leaves are green and the undersides are white. The characteristic flower is similar to a daisy in shape but it is pale yellow on the outer petals, bright yellow on the inner petal with a purplish centre.

Cool season lawns:

Cape daisy can be selectively controlled using any of the commonly used selective broadleaf herbicides. Warm season lawns (Kikuyu, Couch, Seashore paspalum); Mecaprop + Ioxynil (sold Image or Axall)

Chickweed

Chickweed (Stellaria media) and mouse eared chickweed (Ceratium glomeratum) are part of a number of different types of weeds that are referred to as chickweed. Typically Chickweed has long stems with rounded leaves placed as opposing pairs on the stem. The leaves are hairless as are the stems but the leaf stalks are hairy. Whereas Mouse Eared Chickweed is a bluish-green colour and has very hairy leaves and stems. In turf situations they tend to creep along the ground suffocating desirable plants. All chickweeds have small white flowers.

Chickweeds are more difficult to control than many broadleaf weeds as they are not susceptible to 2,4D, dicamba or clopyralid. Picloram & Tricopyr (Triumph, Victory, Tordon Brushkiller) is effective as is Mecoprop & Ixoynil ( Image, Axall). These should be applied at label rates when the turf is actively growing.

Couch Grass

Couchgrass (Cynodon dactylon) is a warm season creeping grass that is sometimes referred to as twitch or Indian doab. The newer cultivars of couch can be used to make a great lawn in warmer climates. However, it is still generally regarded as a weed to many gardeners because of its creeping and spreading growth habit. It produces long creeping stolons (overground runners) and rhizomes (underground runners) that are highly invasive. The stems of these stolons are significantly narrower than that of kikuyu. It is a summer prominent species that tends to go into dormancy over the New Zealand winter. During this period it will stop growing and can often appear quite grey in colouration. As a result, it is normally only used as a turf grass in the warmer parts of coastal New Zealand and prefers dry, warm and sunny areas rather than shady areas where it tends to become sparse. It is a loosely tufted, slightly hairy perennial with long pointed rhizomes. The upper surface of the leaf blade is usually covered with scattered hairs as opposed to the lower surface which is less hairy.

All turf types:

The best measure of control for small infestations is to carefully lift long stolons from the sward and dip or paint on a 3:1 solution of roundup. The active ingredient will translocate through the remainder of the plant. This must be carried out when the plants are actively growing in summer. In the infestation is heavy then the lawn may need a complete spray with round up followed by replacement or re-seeding.Fine Fescue; Control can be exerted by using Haloxyfop-P-Methyl ( sold as gallant or Ignite) The application rate is 37.5 – 50mls per 100m2. At the upper rate some damage may occur to the fescue and because of that we recommend that the lower rate is used as a spot spray treatment to the effected areas only. To ensure that grass is actively growing and healthy prior to treatment a nitrogenous fertilizer application (Turf Gold applied at 3.0kgs per 100m2)is recommended 10 -14 days prior to treatment. In dry weather conditions the lawn should also be irrigated for 7 -10 days prior to application. The best control will occur if the product is applied from November until March when the couch is actively growing.

Creeping Oxalis

Creeping oxalis (Oxalis exilis) is a member of the Oxalidaceae that is a native of New Zealand. Its leaves are comprised of three leaflets that have notches at the tip which is why many people confuse it with clover. It is a perennial plant that grows from creeping stems and stolons which means that it has a tendency to creep over and smother the other more desirable turf species. It is additionally distinguishable by small yellow flowers that are produced for much of the year. It appears to tolerate a wide range of growing conditions from damp poorly drained soils to quite arid environments. Its small size and prostrate growth habit make close cut lawns an ideal habitat for its proliferation. It can be selectively controlled using the active ingredients Picloram & Triclopyr which is sold as the herbicide Triumph Gold.

Creeping oxalis is able to be selectively removed from all cool season turf species using products containing Picloram and Triclopyr such as Triumph, Victory and Tordon Brushkiller. Please note that these products cannot be used on warm season grasses such as kikuyu and couch. For these grasses control is best achieved using repeat applications of 2,4-D & Dicamba (sold as Banvine) or mecoprop, MCPA & dicamba (sold as Broadsword)

Creeping Speedwell

Creeping speedwell (Veronica filformis) is one of four similar forms of veronica that occurs as weeds in lawns. This is a perennial weed that has wide hairy kidney shaped leaf. The stems produce roots to enable them to creep along the ground which creates a very dense mat. This mat suppresses the growth of the desirable turf species. The leaves are dark green and are lightly serrated or toothed. It produces small pale blue or almost white flowers on longish stalks. It is regarded as more difficult to control than the other varieties of speedwell.

All turf types:

Creeping speedwell can be selectively controlled by using bromoxynil & ioxynil & mecaprop. ( Sold as Axall or Image). Repeat applications may be required in circumstances where there is a lot of mature creeping speedwell in the lawn.

Daisy

The common daisy (Bellis perennis) is a troublesome weed which is easily identified by the characteristic white flower with a yellow centre that is often used to make “daisy chains”. It grows as a rosette and belongs to the asteraceae family. These grow as rosettes in the vegetative state which are often joined to gether by subterranean stems

Herbicides containing Picloram appear to be the most effective and this includes products such as Triumph, Victory Gold, & Tordon brushkiller. Be aware the fine fescue and NZ Browntop will discolour if these products are applied during the cooler winter months when the plants are not actively growing. . Therefore it is best to apply this product from September through until April. Fine turf species will also be affected if Brushkiller is applied to lawns that are suffering from heat stress or moisture stress. Therefore, the best control will occur if these species are sprayed prior to flowering and when the grass plants are actively growing.

Dock

Dock (Rumex obtusifolius) is a relatively common tap-rooted weed that in found throughout New Zealand, however because of its size it is not common on lawns. Closely related species such as fiddle dock (Rumex pulcher) and sheep’s sorrel (Rumex acetosella) are likely to be more common in lawns. It has very large (up to 250mm long) wide, erect, round tipped leaved that are bright green in colouration.

All turf types:

Dock is controlled using a selective herbicide such as 2,4D & Dicamba (Banvine) applied at label rates. It is preferable to apply these products from September until May when the plants are actively growing. Fine turf species will also be affected if these products are applied to lawns that are suffering from heat stress or moisture stress. In these circumstances it is advisable to apply fertilizer and irrigate for 7 – 10 days prior to application to ensure that the lawn is in a healthy state prior to spraying.

Hawksbeard

Many lawns become yellow over summer due to mass of yellow flowers appearing from weeds commonly referred to as dandelions. The term dandelion is often used to describe a number of different species. They are all members of the Asteraceae (Compositae) family, all grow as rosettes with tap-roots, have yellow flowers on long green stems, and all produce ‘feathery’ pappus with their seeds, allowing them to be blown around in the wind.

The seedlings of these species are fairly susceptible to most herbicides commonly used in turf. However, because of the large tap-root systems that develop once these weeds get established, older plants are more difficult to control. We recommend using Versatill or Banvine.

Hydrocotyle

Hydrocotyle ( including H.americana, H. heteromeria, H. novae-zeelandiae, H.mochata) is also known as Pennywort. It is a common perennial that grows vigorously via a network of stolons. It has small heavily serrated circular shaped leaves that are light green in colour. It forms a dense mat which suppresses the growth of desirable turf species. It has a distinctive odour when crushed that resembles cat’s urine. It prefers moist, shady areas but will survive well in full sunshine. Some people even use it as the primary composition of their lawn however, it is not durable under heavy or constant wear situations.

All temperate species:

Whilst most normal broadleaf weeds will burn the leaf of Hydrocotyle they will not provide long term control as the plants will recover rapidly. Herbicides containing Triclopyr & Picloram ( eg; Triumph, Victory, Brushkiller) will provide good control. However, this product should only be applied to fine turf species from spring through until mid-autumn when the grass plants are actively growing. Likewise these products should not be applied in hot dry conditions when the plants are under heat stress or moisture stress. NOTE; Products containing Triclpyr or Picloram should not be applied to warm season grasses such as Kikuyu, seashore paspalum or couchgrass

Onehunga Weed

Onehunga weed (Solvia sessilis) is named after the suburb in Auckland where it was first found, though it actually originates from South America. It is most recognisable in the summer months by the spiny seeds commonly referred to as prickles that attach easily to bare feet. It is for this reason that most residential lawn owners wish to have it controlled. Control should preferably occur in July and August prior to the seed setting. It generally germinates in autumn growing initially as rosettes and then producing short prostrate stems. The seeds form at the base of these leaves. Onehunga weed will often invade bare patches on lawns after hot dry summers. These areas should be scarified and re-sown in autumn to avoid re- colonisation by this weed species.

All temperate lawn:

Control Onehunga weed using Triclopyr & Picloram ( Tordon Bruskiller, Triumph, Victory) or Bromoxynil & ioxynil & mecaprop. ( Image, Axall) or Clopralid (Versatil) These products are best applied from July to September prior to seed set. Beyond this period the plants will be adequately controlled however the sharp seeds or prickles will already be present and as such will still be a problem to bare feet. Do not use any products that contain Picloram or triclopyr on kikuyu or couch grass lawns. .

Paspalum

Paspalum (Paspalum dilatatum) is a perennial grass weed that causes problems on lawns throughout the North Island of New Zealand. ( Note that this is significantly different plant to the turf variety known as Seashore paspalum) It is a problem in summer when it produces large numbers of seed heads and its low growing wide leaves hug the ground tending to smother other desirable species. It is dormant for the majority of winter, though the crowns are often still visible in lawns that are cut at a low mowing height. These seed heads are similar to some other types of annual summer grass, which tend to be prominent at the same time of the year. The leaves are dark green in colour and are hairless with the exception of two tufts the at emerge at the base of each leaf blade.

Ryegrass lawns:

Methylarsinic acid (Pasma) is effective if used in November or December. Be aware that Pasma will take out fine fescue grasses also. This is an arsenic based product and therefore it is highly poisonous. For that reason it is not recommended for residential lawns. It is a registered product and as such it can only be sold or applied by a registered user. Additionally, the registered user must have a Stage 2 applicators certificate.The alternative solution is to spot spray the paspalum using Roundup or a similar Glyphosate based product when the plants are actively growing and re-sow those areas in autumn.Fine Fescue lawns: Apply Haloxyfop -P-methyl (Ignite, Gallant) at 50mls per 100m2 when the paspalum is actively growing. Given that this is a high label rate, it is recommended that the Gallant is preferably used as a spot spray treatment otherwise some damage will occur to the lawn, particularly if the lawn is under heat or moisture stress.Other Lawn types:Spot spray the paspalum using Roundup or a similar Glyphosate product when the plants are actively growing and re-sow those areas in autumn.If the paspalum infestation is heavy then we recommend spraying the entire lawn with roundup at 50mls/100m2 preferably twice 21 days apart to ensure an effective kill and then re-sow the lawn.

Pearlwort

Pearlwort (Sagina procumbens) is more accurately called procumbent pearlwort. It is a diminutive bright green coloured plant that has small needle shapes leaves set on opposite sides of a tiny stem. The plant looks similar to and is sometimes mistaken for Irish Moss. It forms a tight, dense mat even in closely mown swards.

Pearlwort can be selectively controlled using herbicides containing Triclopyr & Picloram (Victory Gold, Triumph,Tordon Brushkiller) at recommended label rates.

Poa Annua

Poa annua is an annual grass weed from the large Poa family that tends to act as an annual grass in irrigated situations. This species which is sometimes referred to as “annual winter grass” or “green-keepers curse” is endemic in soils throughout temperate parts of the world. It is a relatively small grass plant which is light green to yellow green in colouration and it seeds prolifically throughout the year. The seeds are white in colour and the leaf blades are soft and often crinkled when young. Poa annua is often confused with poa trivialis which is an annual weed from the same family but is distinguishable by bright green and very shiny leaves. Poa annua seeds prolifically and will seed regardless of cutting height. It is probably the most common grass weed problem for lawns in New Zealand. Typically, it will germinate in the absence of comeptition so is most prevalent on newly established lawns. In the absence of irrigation the plants will die out during the hotter summer months and these plants will not re-emerge. However, in irrigated situations poa annua can behave and persist much in the same manner as a perennial plant. When it behaves in this manner it can be hard to eradicate from temperate grass lawns and several treatments may be required.

Ryegrass, Tall fescue, N.Z. Browntop: Apply ethofumesate (sold as EXPO 500, Ethosin, Claw, Nortron) at 40mls per 100m2. This will need to be applied twice within 28 days. Repeat application every 3 – 4 months if the infestation is bad. Ryegrass only; Ethofumasate acts as a pre-germination spray and as such can be applied directly over freshly sown ryegrass seed to avoid poa annua germinating. Repeat applications will be required every 3 – 4 months. Fine Fescue lawns: Apply Hasloxyfop-P-Merthyl (sold as Ignite or Gallant) at label rates from September through until April. It is advisable not to use this product in winter as it does have a tendency to discolour the fescue. Couch & Seashore paspalum: Use Kerb at label rates Kikuyu; Use Atrazine at label rates

Speedwell

There are four types of speedwell all from the Veronica family. Creeping speedwell is dealt with under its own heading. (See accompanying photographs). The leaves are dark green slightly elongated with toothed margins. The flowers are pale blue or white and are held on relatively small stalks. Speedwell is found as a common weed in many lawns and waste areas in New Zealand.

All turf types:

Speedwell is one of the more difficult to control broadleaf weed species but it can be selectively controlled by using bromoxynil + ioxynil & mecaprop-p.( Axall or Image). Because it is notoriously difficult to control, it is advisable to spray it or dig it out as soon as it is noticed. Products that contain the active ingredients Triclopyr and Picloram will provide a measure of control but this is only temporary.

Summer Grass

Summergrass is a term used to describe a range of annual subtropical annual weeds the seeds of which are endemic in soils in the top half of the North Island. They germinate as a function of light incidence at ground level once ground temperatures exceed about 16 -17C. Because of this they tend to cause most problems in spring or summer sown lawns in the first stage after sowing. Being subtropical plants they grow very rapidly in warm humid conditions. This group of plants includes crowfoot grass (Eleucine indica) summer grass (Digiteria sanguinalis) and smooth summer grass (Digiteria ischaemum). They are annual species and as such they will die and disappear from the sward in autumn when temperatures start to decrease. Quite often they can be mistaken for paspalum because the seed head is similar.

Ryegrass Lawns:

Apply ethofumasate (sold as Expo 500) prior to the anticipated time of germination of these species. This product achieves a high level of success if used as a pre-germination spray. It can also be applied directly onto freshly sown ryegrass seed to prevent these species germinating.Alternatively Pendamethalin can be used as a pre-germination spray. However, this is best used on mature swards over six (6) months of age. This product contains harsh solvents that tend burn ryegrass plants so it is best applied during or just prior to impending rain. Control can also be achieved by applying the active ingredient fenoxaprop-P-ethyl (sold as PUMA S) if you hold an Approved Handler’s certificate.Fine Fescue lawns: Apply Haloxyfop-P-Methyl (sold as Ignite or Gallant) at 60% of label rates when these species are actively growing. Couch & seashore paspalum; Apply flazasulfuron (Katana) at label rates. Kikuyu; Apply Atrazine as a pre-germination application

Twin Cress

Twin cress ( Coronopus didymus) and a similar species called wart cress ( Coronopus squamatus) are common broadleaf weeds in new turf . They belong to the Brassicaceae (Cruciferae) family. These are annuals and as such they tend to dissipate from the sward within 12 months even without chemical intervention. They germinate rapidly after soil cultivation and grow as rosettes when young. Although annual weeds such as this species will die naturally within a year, it is preferable that they are removed early in the establishment phase to assist the development of establishing turf grass seedlings by reducing competition for space and nutrients.

These species are susceptible to most selective broadleaf chemicals. However, because they germinate in large numbers in young turf it is preferable to control them at an earlier stage than other broadleaf weeds. The best solution for this is to apply Inoxynil & Bromoxnil (Axall) at recommended label rates

White Clover

White Clover (Trifolium repens) is a native of Europe and is common in pastures, roadsides, wasteland and lawns throughout New Zealand. It is a legume and as such it is regarded as an important pasture species because of its activity in fixing nitrogen from atmospheric nitrogen. However, it is not welcome as a lawn species because it can be slippery when wet and because it’s flowers attract bees. It is a relatively common weed in lawns throughout New Zealand largely because the seeds can remain viable in the soil for extended periods of time. White clover in particular is easily recognised by the familiar trifoliate leaves and the distinctive white, round flower heads. All the commonly used selective broadleaf herbicides will control white clover in lawns.

Clover is relatively easy to selectively remove from lawns and a wide range of selective broadleaf herbicides can be used successfully. All Lawns; Mecaprop, MCPA & dicamba (sold as Broadsword) or 2,4-D & dicamba (sold as Banvine) applied at label rates will control all species of clover. CAUTION; Triclopyr and Picloram blends (sold as Triumph, Brushkiller, Victory and Tordon Gold) are also effective at controlling clover but these products should not be used on couch, seashore paspalum or kikuyu lawns.

Yarrow

Yarrow belongs to the Asteraceae (Compositae) family, and in the vegetative state resembles a number of other turf weeds from this family. Yarrow ( Achillea millefolium) is often confused with soldier’s button ( Cotula australis). Soldier’s button originates from Australia and so is not native unlike the cotula species (which now belongs to the Leptinella genus) which is commonly used in bowling greens. Yarrow is found throughout the world and originates from Europe. It is a perennial species and has an subterranean rhizome system which spreads to form new plants. This subterranean root system can make control somewhat more difficult and repeat herbicide applications may be required to exert full control.

Clopyralid (versatill) appears to be the most effective herbicide to control this species. Also note that products containing either 2,4D & Dicamba or Picloram & Triclopyr may have some limited success in controlling this species.