Spring Weeds | Turf Journal


By Dr. Eric Reasor
From the February 2023 Concern

The foundation of any turfgrass weed administration program is sustaining an actively rising, wholesome turfgrass stand. Utilizing applicable cultural practices akin to mowing, fertilization, irrigation, and cultivation for the turfgrass species is one of the simplest ways to assist the garden compete in opposition to weeds. Nevertheless, a number of weeds can persist in even essentially the most well-maintained turfgrass. Whereas there’s a rising pattern to tolerate sure weeds which might be pollinator-friendly (e.g., dandelions) or low-growing nitrogen producers (e.g., microclovers), many purchasers nonetheless need a weed-free turfgrass stand. In these situations, herbicide use is usually warranted.

9 of the most typical weeds affecting each warm- and cool-season turfgrass are: crabgrass; yellow and purple nutsedges; kyllinga; dandelion; white clover; oxalis (or yellow wooden sorrel); plantain; prostrate knotweed; and chickweed. Since a few of these weeds have comparable progress and management traits, a number of species might be managed with the identical cultural and chemical measures. Due to this fact, it’s essential to know which weeds are most problematic in your area and develop built-in weed administration packages.

Right here’s an outline of every of the weeds talked about, find out how to establish them, and an summary of the pre- and post-emergent herbicides which might be the simplest in treating them.


(Photograph: PBI-Gordon)

In most areas, crabgrass is a Summer season annual grassy weed. It germinates when soil temperatures heat to 55°F for a number of days. It is very important watch temperatures so herbicides might be utilized earlier than the crabgrass emerges since pre-emergent herbicides are the simplest management. Search for lively elements akin to dithiopyr, indaziflam, pendimethalin, and prodiamine. For maxi- mum efficacy, pre-emergent herbicides should not solely be utilized previous to crabgrass germination, however be adopted by irrigation or rainfall for “activation.”

Submit-emergent herbicides are a terrific instrument to regulate crabgrass that breaks by the pre-emergent herbicides. Examples of those herbicides embody fenoxaprop, fluazifop, pinoxaden, and quinclorac. Submit-emergent herbicides are only at early crabgrass progress phases with the addition of a sprig adjuvant (e.g., MSO, NIS).

Utilizing the identical herbicide repeatedly will ultimately enable for crabgrass immune to that particular mode of motion to populate. Since there’s solely a small number of herbicide modes of motion for crabgrass, it’s very important to handle turfgrass correctly by cultural practices, weed scouting, and utilizing alternate herbicide modes of motion. This may maximize herbicide efficacy and scale back the chance of herbicide resistance.

Yellow & Purple Nutsedges

(Photograph: PBI-Gordon)

Purple nutsedge is extra widespread than yellow in southern areas. Each have triangular-shaped stems and a shiny leaf look. Distinguishing purple nutsedge from yellow nutsedge might be considerably difficult with out the presence of seed heads. Purple nutsedge leaves are abruptly pointed. Yellow nutsedge leaves slowly taper to some extent. Each species have underground tubers and rhizomes that enable them to unfold and return year-to-year. Nutsedges may also unfold by way of seed. Nevertheless, their viability is comparatively low in comparison with different weed species.

Nutsedges want moist soil situations, however can persist in many alternative environments. Cultural management measures could not present acceptable management. Luckily, there are a number of herbicide-active elements. Some lively elements embody sulfentrazone, halosulfuron, flazasulfuron, trifloxysulfuron, imazosulfuron, and pyrimisulfan. You’ll want to learn the herbicide label previous to any utility to be used on the particular turfgrass species.

Kyllinga Species

(Photograph: Adobe Inventory / Nophara)

Kyllinga species are weeds within the sedge (Cyperaceae) plant household, however they aren’t nutsedges. There are lots of completely different kyllinga species that may infest turfgrasses. The most typical and troublesome to regulate are inexperienced kyllinga and false-green kyllinga. These perennial weeds can kind a dense cover to outcompete turfgrasses year-after-year. Inexperienced and false-green kyllinga sometimes have a finer leaf texture and a lighter-green colour than nutsedges. They’re additionally prone to have small and burred spherical seed heads on the base of the leaves even when commonly mowed. Kyllinga do not need any underground tubers, however they do possess a dense rhizome system. Like nutsedges, kyllinga want moist soil situations but in addition can persist in numerous environmental situations.

Mowing peak is likely one of the most essential components for managing kyllinga in lawns. Growing the mowing peak, particularly with cool-season turfgrass, can provide the turfgrass an edge in competitors.

The identical herbicide lively elements used for nutsedge can be utilized for kyllinga. Relying on the turfgrass species, sulfentrazone, halosulfuron, flazasulfuron, trifloxysulfuron, imazosulfuron, and pyrimisulfan herbicides can present kyllinga management.


Spring weeds
(Photograph: PBI-Gordon)

Widespread dandelion is likely one of the most recognizable weeds on this planet and probably the most prevalent in maintained turfgrasses. The enduring yellow flower on the tall, hole stalk is definitely identifiable. The yellow flowers then mature into the white “puff balls” or “blow balls” when the seeds develop and are prepared for wind and visitors dispersal, typically spreading all through massive areas.

Beneath mown situations with out the yellow or white flowers, dandelion leaves can be utilized to establish the species. Dandelion leaves are deeply lobed or toothed with an rectangular or spatulate form. The leaves kind a rosette which may encompass many leaves. Dandelions even have a deep taproot and milky sap.

There are quite a few herbicides labeled for dandelion management in turfgrasses. Most of those herbicide lively elements are thought of “broad spectrum” broadleaf herbicides; nonetheless, sure herbicides used for grassy weed management can present dandelion management. A number of the commonest lively elements used for dandelion management are 2,4-D, carfentrazone, fluroxypyr, MCPP, MCPA, mesotrione, metsulfuron, penoxsulam, quinclorac, and triclopyr.

Herbicide choice will depend on the turfgrass species, web site, and value. Herbicides are additionally much less efficient throughout peak dandelion bloom than they’re pre- and post-bloom. Submit-dandelion bloom might not be the very best utility timing both because of the seed manufacturing and dispersal of dandelion.

White Clover

Spring weeds
(Photograph: PBI-Gordon)

White clover is one other extremely recognizable weed in maintained turfgrasses. Present in warm- and cool-season turfgrasses, white clover is a perennial broadleaf and may tolerate a variety of mowing heights and environments.

The weed might be simply recognized by its leaves and flowers. White clover leaves are a trifoliate leaf association, with three spherical/elliptical leaflets, and sometimes have a white watermark that partially encircles the bottom of every leaflet. White clover produces white flowers on lengthy stems which might be largely current in Spring and Fall. Most lively white clover progress is in Spring and Fall and spreads from stems and stolons that root on the nodes and may kind dense mats or clusters.

White clover is a legume, so it will probably repair its personal nitrogen and may persist in N-deficient turfgrasses. Growing N fertilization and lowering soil moisture are two glorious cultural practices for managing white clover. Since white clover is a perennial weed, pre-emergent herbicides
usually are not readily efficient. Nevertheless, quite a few post-emergent herbicide choices can be found.

Herbicides that comprise three or extra phenoxy or phenoxy-type lively elements have proven to supply nice management. Some particular lively elements for clover management are carfentrazone, dicamba, fluroxypyr, halauxifen-methyl, MCPP, MCPA, mesotrione, metsulfuron, penoxsulam, quinclorac, and triclopyr. You’ll want to learn all herbicide labels prior to make use of.

Herbicide resistance is just not a widespread drawback in white clover; nonetheless, it’s all the time doable for any weed to develop resistance. It’s essential to use herbicides at labeled charges and alternate modes of motion.

Oxalis Species

Spring weeds
(Photograph: PBI-Gordon)

Oxalis is a gaggle of species generally known as woodsorrels. There are a number of woodsorrels problematic in turf, however essentially the most prevalent is yellow woodsorrel. It’s a perennial, cool-season weed and grows in a extra upright behavior than white clover.

Yellow woodsorrel weed can look just like clover with a trifoliate leaf association. Nevertheless, it has heart-shaped leaflets as a substitute of spherical. It additionally produces small yellow flowers that distinguish it.

Herbicide management of yellow woodsorrel might be fairly troublesome. Herbicide mixtures that comprise three or extra phenoxy lively elements may not present ample management. Further herbicide lively elements to incorporate in functions to assist in herbicide management are as carfentrazone, halauxifen-methyl, mesotrione, metsulfuron, penoxsulam, and sulfentrazone.

Plantain Species

Spring weeds
(Photograph: PBI-Gordon)

Broadleaf and buckhorn plantain are perennial broadleaf weeds present in many sorts of turfgrass. Broadleaf plantain has spherical leaves, whereas buck- horn plantain has slim, lance-shaped leaves. Each species have noticeable parallel leaf veins inflicting them to be simply misidentified with each other. The leaves develop in a rosette with a taproot, and seed heads develop on tall stalks.

Like dandelion, there are quite a few herbicides labeled for plantain management. A number of the commonest lively elements used for management are 2,4-D, carfentrazone, dicamba, fluroxypyr, MCPP, MCPA, metsulfuron, penoxsulam, quinclorac, and triclopyr.

There have been documented instances of herbicide-resistant buck- horn plantain species on account of overuse of group 4 herbicides (e.g., 2,4-D, dicamba, and triclopyr). This situation is just not widespread throughout the nation, although it’s important to alternate or mix a number of herbicide modes of motion to mitigate herbicide resistance.

Prostrate Knotweed

Spring weeds
(Photograph: PBI-Gordon)

Prostrate knotweed is a Summer season annual broadleaf weed. It germinates in early Spring, sometimes previous to crabgrass germination. Knot- weed seedlings can resemble grass seedlings quickly after emergence however will develop oval-shaped leaves and kind dense mats. It may possibly out- compete turfgrass in compacted soils and is taken into account an indicator of compaction. If knotweed is a persistent drawback, contemplate lowering compaction with aeration.

Most pre-emergent herbicides will present acceptable management. Nevertheless, utility timing is essential as a result of knotweed germinates previous to crabgrass. The lively elements in pre-emergent herbicides that present acceptable management embody, however usually are not restricted to, prodiamine, dithiopyr, pendimethalin, indaziflam, and isoxaben.

Submit-emergence knotweed management is usually a lot simpler when herbicides are utilized earlier within the season. The dense cover and thick stems of mature crops could make management troublesome in late Summer season. Typical 3- and 4-way herbicide mixtures containing 2,4- D, dicamba, carfentrazone, fluroxypyr, or triclopyr can present acceptable post-emergent management.


Spring weeds
(Photograph: PBI-Gordon)

Chickweed is a gaggle of Winter annual weeds present in each cool- and warm-season turf- grasses. Widespread and mouse-ear chickweeds are two which might be sometimes problematic. They germinate in Fall with cooler soil temperatures. Widespread chickweed has small leaves that come to some extent and small white flowers. Mouse-ear chickweed leaves are additionally small, however are very bushy and oval to rectangular formed. Each species can develop upright if not mown however will adapt to mowing by rising prostrate and forming a dense cover.

Chickweeds might be problematic in Spring if not managed in Fall or Winter. The crops might be extra mature and reproducing by way of seed in Spring. Each species are shallow-rooted, so correct irrigation practices are essential, particularly in Fall and Winter when irrigation wants of turfgrass are a lot much less.

Management of chickweed is easy with applicable timing. If utilized previous to germination in Fall, pre-emergents that present acceptable management embody, however aren’t restricted to, prodiamine, dithiopyr, pendimethalin, indaziflam, and isoxaben. If utilizing a post-emergent, most broad spectrum, broadleaf merchandise present acceptable management if utilized previous to Spring seed manufacturing.

Reasor, Ph.D, is Southeast Analysis Scientist with PBI-Gordon Company the place he’s accountable for coordinating all analysis protocols, technical help to cooperators, and product help for channel companions and end-users in 10 states. Reasor holds a Ph.D. in Turfgrass Weed Science from The College of Tennessee, the place he carried out analysis packages for “off-type” grasses in bermudagrass placing greens, participated in extension actions, and managed weed science analysis packages. He earned his Grasp of Science in Plant Sciences from The College of Tennessee, and a Bachelor of Science in Crop and Soil Environmental Sciences from Virginia Tech College.

Do you might have a remark? Share your ideas under, or ship an e-mail to the Editor at cmenapace@groupc.com.


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