Weed of the Month for November 2014 is Roughstalk Bluegrass

Roughstalk Bluegrass  

Biology: Roughstalk bluegrass, primarily known by its scientific name (Poa trivialis), is a cool-season perennial grass that can be found throughout the Midwestern United States. Though roughstalk bluegrass can be found in landscapes, roadsides, meadows, and waste areas, it is primarily considered a turfgrass weed. It can successfully germinate in multiple environmental conditions, but it has a preference for moist soils and high levels of shade. This ability to successfully establish in conditions ideal for the growth and development of most turfgrass species, as well as its ability to spread throughout the turfgrass canopy by stolons, make roughstalk bluegrass a common turfgrass weed throughout the state of Indiana.

Identification: Roughstalk bluegrass is a cool-season perennial grass that can be found in both high- or low-maintenance turfgrass throughout the Midwestern United States. Though the plant looks like it has clumping growth patterns, the plant survives from year-to-year through creeping, above-ground stems called stolons, which spread easily throughout the surrounding turfgrass canopy. Seedlings of the plant are generally small and slow to establish compared to other turfgrass varieties. Despite being included in turfgrass seed mixtures for shady areas, roughstalk bluegrass is also a common contaminant of uncertified turfgrass seed mixtures, and will successfully germinate alongside the desired turf species with adequate soil temperature and moisture conditions. Roughstalk bluegrass leaves are folded in the bud with a membranous ligule that can range from absent to very distinct (long) in size (NOTE: when samples are sent to me for identification, it is usually the type with no or very short ligules). The presence of very small, scabrous hairs give the leaf surface and margins a rough feel, thus accounting for the common name ‘roughstalk bluegrass’. The plant has a broad collar and a boat-shaped leaf tip that is characteristic of other bluegrass turf species. The leaves are shiny, and are pale green or yellow-green in color, but they often turn red or maroon during periods of drought or heat stress. Seedheads are produced from mid-May through June in an open panicle similar to that of Kentucky bluegrass. Roughstalk bluegrass can remain green throughout the winter (with some minor leaf-tip burn) and during the summer months it generally goes dormant. Stolons can successfully germinate after many years of prolonged dormancy. It is often confused with other bluegrass species such as annual bluegrass, though it is considerably larger, and Kentucky bluegrass, though it is generally lighter green in color. Annual bluegrass is primarily bunch-type. Kentucky bluegrass has rhizomes (underground creeping stems). Roughstalk bluegrass can also be confused with creeping bentgrass which is also stoloniferous; however, creeping bentgrass is rolled in the bud while roughstalk bluegrass is folded in the bud.  

Rough bluegrass stolon.

New growth emerging from a node on a rough bluegrass stolon in September following summer stress.

Most rough bluegrass samples have a small or absent membranous ligule with no visible auricle present.

Heat stress in summer will start off as a purpling of the leaves.

Patches of rough bluegrass turn brown.

Eventually rough bluegrass patches will enter summer dormancy and appear dead.

This golf course had a lot of rough bluegrass which created a perennial problem of summer decline in their fairways.

Green stolons look like spaghetti.

Green stolons look like spaghetti. Stolons easily pull up in summer when plants are stressed and rooting is poor.

Cultural control: Rough bluegrass likes shady, wet areas. Therefore, reduce irrigation frequency to reduce the spread of this grassy weed. Mowing practices alone will not provide adequate management since roughstalk bluegrass can survive in many of the same environmental conditions and management programs as other desired turfgrass species. The best method of cultural control for roughstalk bluegrass is to avoid contaminating your turf system in the first place by buying certified seed mixtures/blends from a reputable seed company. Carefully read the labels of each seed bag. Unless the seed is advertised as a shade tolerant mixture, make sure roughstalk bluegrass species are not mentioned in the varieties of seed contained within the bag as a 'weed seed'.

Biological control: None known specifically for roughstalk bluegrass.

Chemical control: Small areas and patches of roughstalk bluegrass can possibly be managed by making repeat applications of non-selective herbicides such as glyphosate and glufosinate; however, complete control is difficult due to the survival of creeping stolons.Spring application timings before the stress of summer will aid in the control of rough bluegrass with these non-selective herbicides.

For golf courses and sod farms, other products exist that are not labeled for use in lawns. For more information on these products and on weed control, check out our Turfgrass Weed Control for Professionals Publication.

For archives of past weed of the month postings, visit our Weed of the Month Archive.

Aaron Patton, Turfgrass Extension Specialist
Leslie Beck, Postdoctoral Research Associate
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Weed of the month for October 2014 is Buckhorn Plantain

Buckhorn Plantain  

Biology: Buckhorn plantain (Plantago lanceolata) is a perennial broadleaf that can be found in sites that are typically dry and consist of neutral to basic soils. Like the closely-related broadleaf plantain (Plantago major), buckhorn plantain can often be found in compacted soils but does not tolerate injury from constant traffic stress. It germinates by seed typically in spring or fall. Seeds have the ability to germinate in relative darkness and can successfully establish and develop into a mature plant; even when surrounded by tall, dense turf. These factors, coupled with its ability to survive low mowing heights, make buckhorn plantain a common weed in low or high maintenance turfgrass.

Identification: Buckhorn plantain is a perennial broadleaf weed that can be found in high and low-maintenance turf throughout the Midwestern United States. The plant produces a dense network of fibrous roots. Buckhorn plantain forms a central, basal rosette. Though it is a broadleaf weed, the first leaves (cotyledons) of the germinating plant are grass-like in appearance and are hairy only on the outer edge of the leaf (margins). As the plant matures, leaf clumps remain in a basal rosette; however, mature plants have the ability to produce multiple clumps all originating from the same crown. The leaves are spear- (lanceolate) to narrowly oval-shaped, are widest at just above the middle point of the leaf length, and are often twisting or heavily curled. Very prominent leaf veins run parallel to the leaf margins which may be entirely smooth or slightly toothed. These leaf veins form prominent ridges that can be easily seen and felt along the lower surface of the leaf. Leaf blades are generally smooth, but can occasionally have long, silky hairs at the base, and are bright to dark-green in color. In a taller turfgrass canopy, the leaves can grow more erect. As the mowing decreases in height and increases in frequency, leaf growth will be more prostrate along the surface of the turfgrass canopy. Small white flowers can be seen branching from dense, cone-shaped seedheads held aloft on an erect, leafless, hairy stalk from June throughout September. In yards that are infrequently mown in the Midwest, the appearance of hundreds of erect buckhorn plantain seed stalks can increase the look of a ‘weedy’ lawn during the summer months. Buckhorn plantain may be confused with bracted plantain (Plantago aristata); however, it has narrower, and hairier leaves and lack the deep, prominent leaf-vein ribs that are characteristic of buckhorn plantain. Buckhorn plantain may also be confused with broadleaf plantain; however, broadleaf plantain has much longer spike-inflorescence (not cone-shaped) and leaf veins appear to originate from a very distinct attachment point to a long, broad leaf-stem (petiole). Buckhorn plantain leaves originate from a very short stem which forms the basal rosette.

Buckhorn plantain grows in clumps of leaves which originate from a central rosette.

Buckhorn plantain leaves have parallel leaf veins that form very deep, prominent ridges.

 Dense population of buckhorn plantain.

 Cone-shaped seedhead with small white flowers.

 Dense groups of seedhead can often appear in lawns that are infrequently mowed. These seedheads can make lawns look very 'weedy', even from a distance.

 Multiple clumps of bright green buckhorn plantain leaves in a droughty cool-season lawn.

Though the plants are related, the leaves of broadleaf plantain (left) are much more broad with leaf margins that originate from the leaf stem (petiole). Buckhorn plantain leaves (right) are more narrow with seemingly parallel leaf venation.

Cultural control: None known specifically for buckhorn plantain. Since its primary method of dispersal is through seed, control or removal of the plant prior to seed production is crucial for deterring the spread of the weed. However, mowing practices alone to remove the seed stalks prior to germination will not provide adequate management since the vegetative portion of the plant can tolerate very low mowing heights. Additionally, since multiple plant clusters can originate from the same crown, it is possible to hand-weed buckhorn plantain; however, it is crucial to remove the crown to prevent regrowth.

Biological control: None known specifically for buckhorn plantain.

Chemical control: Both buckhorn and broadleaf plantain can be chemically controlled using similar herbicide products. Repeat applications of two- or three-way mixtures contianing 2,4-D, MCPP, or MCPA are available in multiple formulations at local retailers and can provide adequate control of buckhorn plantain. Additionally, herbicides that contain triclopyr (Turflon Ester) or triclopyr in combination with other herbicides, such as 2,4-D, can also control buckhorn plantain in cool-season grasses. For best results, herbicides should be applied when buckhorn plantain is actively growing. Follow the directions on the product label for suggestions on improving herbicide efficacy through mowing and irrigation practices prior to- and following the herbicide application.

For more information on weed control, search this blog and check out our Turfgrass Weed Control for Professionals Publication.

For archives of past weed of the month postings, visit our Weed of the Month Archive.

Aaron Patton, Turfgrass Extension Specialist
Leslie Beck, Postdoctoral Research Associate
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December Workshops for the Crew: Weed Identification & Control (Herbicide Workshop) and NEW Equipment Technician Training Workshop

Two workshops are available for you and your crew this December.

First, a new workshop, Equipment Technician Training is available. On December 11, 2014 we are hosting our first equipment technician training opportunity at the W.H. Daniel Turfgrass Research and Diagnostic Center in West Lafayette, Indiana. The training is meant for anyone who has some level of responsibility (managers and technicians) for maintaining equipment and those interested in learning more on the subject.

Workshop Brochure | Register by scan/email, fax or mail or Register online.

Participants at this workshop will learn reel grinding fundamentals with hands-on demonstrations.

Second, what is becoming a popular classic, the Herbicide Workshop. This one day workshop is designed for beginners and for more experienced professionals who want more information on herbicide use principles and discussion of how to control the most common weeds in turf. This workshop offers training inweed identification, integrated weed management, herbicide mode of action, and weed control principles. The workshop is held in four locations (including a Chicagoland location) this year.

December 2, 2014, West Lafayette, Indiana
Registration Brochure (PDF) | On-line Registration
December 4, 2014, Indianapolis, Indiana
Registration Brochure (PDF) | On-line Registration
December 9, 2014, St. Charles, Illinois
Registration Brochure (PDF) | On-line Registration
December 11, 2014, Fort Wayne, Indiana
Registration Brochure (PDF) | On-line Registration

Over 70 different live weed samples will be showcased at this event in addition to great content on weed control.
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2015 Great Lakes School of Turfgrass Science Online (For Professionals)

Any investment in quality continuing education opportunities benefits employees and employers alike. The 2015 Great Lakes School of Turfgrass Science Online is designed to help meet the continuing education needs of any individual or organization.  This 12-week program will have training sessions accessible live online on Wednesday evenings from 6 to 8pm (Central Standard Time) or the option to view the recorded sessions. This 12-week certificate-based program aims to provide participants with thorough and practical continuing education in turfgrass management.  The course is directed by educators from the University of Minnesota-Twin Cites and the University of Wisconsin-Madison, with 12 turfgrass scientists and educators from eight Land-Grant Universities.

Turfgrasses are a resource in our urban community environments and best management practices are aligned with environmental, economic & societal priorities. The Great Lakes School of Turfgrass Science provides participants with the science based principles needed to effectively manage turf for recreation, sport, aesthetics and environmental protection. The Great Lakes School of Turfgrass Science is a quality training opportunity for:
  • Practitioners that establish and maintain turfgrass for athletic fields, consumer/commercial lawns, golf courses, recreation/parks, and sod production
  • Technical representatives from industry (suppliers of equipment, plant protectants, fertilizer, etc.)
  • Those new to the industry – wanting to get trained and off to a great start
  • Those with experience in the industry – to review/update their knowledge and practices
The registration deadline is December 31st, 2014. Students will have access to the course and materials at their convenience during the 12-week period via moodle class management system.  The fee for the course is $495, which includes supplemental materials and a certificate after successful completion of the program.  Visit this link to register: http://z.umn.edu/2015greatlakesturfschool

Early registration is encouraged and pre-registration is required.

For Further Information: Contact Sam Bauer, Assistant Extension Professor – University of Minnesota, Email: sjbauer@umn.edu Phone: 763-767-3518.

The Midwest Regional Turf Foundation is a supporting partner of this short course and Purdue's Dr. Aaron Patton is one of the instructors. We encourage you to consider this new, online education opportunity.



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Is it Too Late to Apply My Last Nitrogen Fertilization?

Fall is an important time to fertilizer our cool-season turfgrasses. Fall nitrogen promotes good root development, enhances storage of energy reserves, and extends color retention in cool-season lawns. Most of the benefits from late fall nitrogen will be seen next spring and summer with earlier green-up, improved turf density, and improved tolerance to spring diseases such as red thread and pink patch, and reduced weeds.

Historically, we recommended applying more nitrogen in late-fall than we currently recommend. While we used to recommend applying 1.0-1.5 lbs N/1000 square feet with a quick-release nitrogen fertilizer in early to mid-November, we now recommend lighter rates of 0.5-0.75 lbs N/1000 square feet with a quick-release nitrogen fertilizer in early to mid-November. In southern Indiana, a late November or early December application timing would be similar to a mid-November application timing in north central Indiana as there is about a 3 week gap in seasons between the northern and southern ends of the state.

This fall has been cooler than average, especially in November. We are not used to having snow on the ground in mid-November. This caught many by surprise and they were unable to get their last round of nitrogen fertilization out onto the turf. Now, they are wondering if it is too late or not to apply some nitrogen fertilizer if we have a few mild days in late November and early December here in Indiana.

Q: Is it too late to apply nitrogen to cool-season turf (November 26, 2014)?
A: In my opinion, the answer is yes. It is too late to apply nitrogen in 2014 and here is why.
Nitrogen uptake decreases as temperatures cool in autumn.  Since growth and transpiration is slow when temperatures are cool in late-fall, nitrogen is taken-up at lower rates. As such, if you apply nitrogen now when it is cool and temperatures are just a few (<10 °F) degrees above freezing, not all of it will be taken-up by the plant and the remaining nitrogen will stay in the soil or could be prone to loss from leaching.

Fertilizer should not be applied when snow is on the ground or when the ground is frozen as this will make the nitrogen more subject to runoff.

Q: What should I do now since I didn’t get my last application out?
A: Do nothing now. We just missed our opportunity to fertilize in late-fall because of the weather. It happens! While the forecast may have a few days at 50°F or higher predicted in the near future, turf growth, transpiration, and nutrient uptake will be minimal for the remainder of the calendar year as most days will have highs just above freezing.

If you were able to apply some nitrogen in August, September, or October, you should have few worries as you applied nitrogen during the most important part of the year which is at the end of the summer or start of the fall. If the turf seems lean next spring because you missed your late-fall nitrogen application, consider applying a little extra (0.25-0.5 lbs N/1000 square feet) nitrogen fertilization in late April or early May after the spring growth flush to help thicken the turf. Use a slow-release nitrogen source for this spring application.

The ongoing research we have on this topic of late-season nitrogen applications is active and much is being explored on this topic.

Below are a couple examples of research published on this topic in the past few years. Several more experiments are ongoing and we will continue to keep you informed as new research develops.

1. Bigelow, C. and others. 2013. Cool-Season Lawn Turf Response to Fall Applied Nitrogen Programs in the North Central States. Available at: https://scisoc.confex.com/crops/2013am/webprogram/Paper80460.html
2. Lloyd, D.T., D.J. Soldat, and J.C. Stier. 2011. Low-temperature Nitrogen Uptake and Use of Three Cool-season Turfgrasses under Controlled Environments. HortScience 46(11):1545-1549.
Restricted access to full report. Available at: http://hortsci.ashspublications.org/content/46/11/1545.short

More fertilizer program information is available in AY-22: Fertilizing Home lawns at http://www.extension.purdue.edu/extmedia/AY/AY-22-W.pdf

Aaron Patton, Turfgrass Extension Specialist
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Weed of the month for September 2014 is Broadleaf Plantain

Broadleaf Plantain  

Biology: Broadleaf plantain (Plantago major) is a perennial, broadleaf weed that can be found in nutrient-poor soils; however, they prefer nutrient rich-soils that are moist and often high in calcium. Broadleaf plantain is a common weed in turfgrass, nurseries, and landscapes as it can tolerate very low mowing heights. It germinates from seed in late spring through mid-to-late summer and occasionally in the fall depending on temperature and moisture. It has a low growing rosette habit and tolerates close mowing. It's ability to surve a range of environments make broadleaf plantain a common turfgrass weed in North America.

Identification: Broadleaf plantain is anchored primarily by fibrous roots. Some describe the root system as having a central, short taproot with branched-out fibrous roots but my experience is that large, fibrous roots are common and that taproots (especially large taproots like a dandelion) are very uncommon. Broadleaf plantain grows with a rosette habit with leaves that can grow flat along the turfgrass canopy or more erect and upright depending on mowing practices. The plant produces leaves that form on long, broad leaf-stems (petioles) that may grow up to six inches long and four inches wide when left unmown or untreated. Young leaves are oval to egg-shaped, generally have 3-5 prominent veins, and are light green in color. As the plant matures, the leaves start to appear darker green, can be smooth or slightly hairy, and abruptly narrowing to the petiole (leaf stalk). Very prominent leaf veins run parallel to the margin and appear to originate from the attachment point at the petiole. Leaf margins are smooth (entire) and appear more crinkled and wavy as the plant matures. Though the leaves can appear waxy and dark- to bluish-green, the petioles often have a reddish color towards their base, or the origin point of the rosette. Broadleaf plantain can produce flowers from June through September on long, leafless flower-stalks that arise from the center of the rosette. Small, whitish petals emerge from the flower-stalk where seeds are produced in an oval-shaped capsule which can contain up to 30 viable seeds. It may often be confused with blackseed plantain (Plantago rugelii) which is similar in appearance. Additionally, it is thought that many plants characterized as broadleaf plantain may in fact be natural crosses between Plantago major and Plantago rugelii.  

Broadleaf plantain appearance in early spring. it will regrow all its leaves each spring. The purple coloring here is in response to cool, spring temperatures.

Cultural control: None known specifically for broadleaf plantain. Since its primary method of dispersal is through seed, control or removal of the plant prior to seed production could reduce the spread of this weed. However, mowing practices alone to remove the seed stalks will not provide adequate management since the plant can produce viable seed at low mowing heights (produces viable seed at about 2 inches and taller heights of cut). Proper turf management such as higher mowing heights, irrigation, and fertilization will help to produce a dense, aggressive turf which is the greatest defense against invading/germinating weeds. Broadleaf plantain thrives in compacted soils, moist or dry soils, and shady conditions. Some research suggests as well that this plant prefers high calcium soils, but high calcium soils are a common phenomenon in North American because the soil parent material is limestone. Plants can be removed by hand-weeding if there are only a few on the property.

Biological control: None known specifically for broadleaf plantain. Many new organic products contain the active ingredient iron HEDTA (FeHEDTA). Multiple applications of this product are required for control. FeHEDTA containing products injure turf less (can actually make turf darker green), but their efficacy for weed control is yet to be well documented.

Chemical control: Broadleaf plantain can be chemically controlled with several products such as repeat applications of two- or three-way mixtures of 2,4-D, dicamba, MCPP, or MCPA which are available in multiple formulations at local retailers. 2,4-D is the active ingredient that does most of the work in these mixtures. Herbicides that contain triclopyr (Turflon Ester) or triclopyr in combination with other herbicides, such as 2,4-D, can also provide good broadleaf plantain control in cool-season grasses.

For more information on weed control, search this blog and check out our Turfgrass Weed Control for Professionals Publication.

For archives of past weed of the month postings, visit our Weed of the Month Archive.

Aaron Patton, Turfgrass Extension Specialist
Leslie Beck, Postdoctoral Research Associate
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Armyworms Invade Indiana

There appears to be a wide-spread outbreak of armyworms [Pseudaletia (=Mythimna) unipuncta (Haworth)] infesting residential turf across southern Indiana. These insects typically have 2 generations per year in this part of the country and we are in the midst of the 2nd generation of larvae. Adult armyworm moths lay their eggs in large masses and when the eggs hatch, the resulting caterpillars begin to feed and move across the infested area. When the larvae are small, this feeding causes little damage and may go unnoticed. However, As development proceeds, the larvae increase in size, consuming larger amounts of turf.
Armyworm taken from turfgrass in southern Indiana. Photo courtesy of B. Voges.

Where heavy infestations occur, a typical home lawn may seem to disappear almost overnight!! Feeding damage often appears to radiate out from a central point where the main infestation likely started. Although the damage can be alarming, armyworms are easily controlled with insecticides and the damage they cause, although unsightly, will not permanently damage the turf unless it is already stressed from drought.

A home lawn in southern Indiana showing typical armyworm damage. Photo courtesy of B. Voges.

Fortunately, most of Indiana has been experiencing adequate rainfall for the last few weeks, so turf should be resilient to this damage. Still, expect damage to get worse before it gets better. Good cultural practices including adequate fertility and irrigation will help the turf recover more quickly. The caterpillars we are seeing now will pupate by the end of September and attempt to remain in the soil over winter. Unless we experience an exceptionally mild winter, most pupae will not overwinter successfully.

For control information go to: http://extension.entm.purdue.edu/publications/E-61.pdf

Doug Richmond, Turf Entomologist
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Words You Might Hear a Turf Nerd Use

A nerd is an intelligent but single-minded person obsessed with a nonsocial hobby or pursuit1. Therefore, a turf nerd is someone single-minded towards turf, obsessed with turf, and a bit nonsocial. I suppose that described me pretty well.

To help increase your turf nerd quotient (only nerds use words like quotient), I thought I would educate you about 12 words that you might hear a turf nerd use. Try your best to weave one of them into a conversation this week.

12 Words You Might Hear a Turf Nerd Use:

agrostology – the branch of systematic botany that deals with grasses2. Some of the first turf scientists in the country were first called agrostologists in the early 1900s.

anaeraobic – the absence of molecular oxygen2. This term is usually used when discussing soils. A soil that is anaerobic is lacking on oxygen. A wet or water-logged soil is anaerobic. Without oxygen in the soil plants suffer and shifts in bacterial populations occur.

apomixis – the laymen’s definition is “clonal reproduction through seeds” which is also known as agamospermy.  This one gets complicated, but all you need to know is that Kentucky bluegrass is apomictic which means that when you buy a particular cultivar of Kentucky bluegrass (Poa pratensis), all the seed you plant will essentially grow-up to be genetically identical to the parent plant. With many other cool-season turfgrass species, the individual seeds are produced through sexual reproduction (intercrossing) of plants with similar traits which results in individual plants within a cultivar that are almost identical or very similar but technically genetically different than one another. Vegetative apomixis can also occur such as with bulbous bluegrass (Poa bulbosa).

cation – a positively charged ion2. Examples include calcium (Ca), magnesium (Mg), sodium (Na), and hydrogen (H). These will commonly be referred to as cations on a soil test report. Cation exchange capacity is a measure of the soils ability to retain these positively charged cations on the soil colloid which is negatively charged.

desiccation – the process of being desiccated (which is to dry up) due to the deprivation (another nerdy word) of water2. Desiccation or drying out is a common term used to describe a specific type of winterkill than can occur in turf when no snow fall is present and when wind speeds are high and windy days are frequent. Desiccation injury to turf is more common in the plains in states such as Nebraska.

dioecious – having staminate and pistillate flowers on separate plants2. A plant that has separate male and female flowers that usually occur on separate plants. Buffalograss is an example of a turf that is dioecious.

Male flower

Female flower or burr.

glabrous – having a smooth surface, without hairs2. When you want to describe that a grass plant is smooth and without hairs, use the term glabrous. The Kentucky bluegrass had a glabrous leaf blade. The opposite is pubescent which means covered with short hairs3.

hygroscopic – readily capable of absorbing and retaining water from the atmosphere, under normal conditions of temperature, pressure, and humidity2. You all have experienced this phenomenon whether you know it or not. Most fertilizers are hygroscopic. When you open the fertilizer bag and then come back a few weeks later and all the fertilizer is stuck (caked) together, it is due to the fertilizers hygroscopic nature.

marcelling – A wavy or washboard pattern on the surface cutting plane of mowed turfgrass; usually results where the clip of the reel exceeds the mowing height4. Marcelling is specific to reel mowers and not an effect seen with rotary mowers.

Look for the parallel lines running NNW. This is Marcelling.

mat – Thatch intermixed with mineral matter that develops between the zone of green turf vegetation and the original soil surface; commonly associated with golf course putting greens that have been topdressed2.

rachilla – subdivisions or branchlets of the rachis that support individual flowers, (seeds), within the spiklet of grasses2. The axis of a grass spiklet3. This is the little golf tee looking appendage on a turf seed.

verdure – the quantity of green living plant tissue per unit land area remaining above the soil following mowing at a specified height and usually expressed on a dry weight basis2. Essentially, this is how much turf is left above the soil surface after mowing. We often measure the mass or the quality (carbohydrates, mineral content, etc.) of verdure in turf research.

I hope you enjoyed this post.

Aaron Patton, Turf and Weed Scientist, Purdue University

  1. http://dictionary.reference.com
  2. From or adapted from Beard, J.B., and H.J. Beard. 2005. Beard’s Turfgrass Encyclopedia for Golf Courses, Grounds, Lawns, Sports Fields. Michigan State University Press, East Lansing.
  3. Harris, J.G., and M.W.. Harris. 2001. Plant identification terminology: an illustrated glossary. Spring Lake Publishing, Payson, UT.
  4. Turgeon, A.J. 2008. Turfgrass Management. Pearson Education, Inc. Upper Saddle River, New Jersey.
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Weed of the month for August 2014 is Prostrate Spurge

Prostrate Spurge  

Biology: Prostrate Spurge (Euphorbia humistrata) is a summer annual broadleaf weed that can be found in dry/sandy and/or nutrient-poor soils along with compacted, weakened or disturbed turfgrass and landscape sites. Look for it first in driveways and sidewalks or in potted plants in a landscape or nursery as temperatures start to get warmer. Prostrate spurge can also be found in cultivated fields, brick walls, and parking lot cracks. It germinates from seed in June and July in Indiana and spreads via low-growing prostrate stems than form a dense mat as they invade the turf canopy. Its ability to establish and grow in multiple soil/climate conditions and highly compacted soils, as well as its ability to withstand low mowing heights, make prostrate spurge a common turfgrass weed throughout the state of Indiana.

Identification: Prostrate spurge is a low-growing summer annual weed in Indiana. The plant is anchored by a central shallow taproot and, as suggested by its common name, it forms a ground-hugging mat with prostrate stems that grow outward throughout the turf canopy. The plant produces these spreading stems along with viable seed very quickly, often within a couple of weeks after germination.

The leaves of prostrate spurge are pale green, hairy, egg-shaped, widest at the apex, and located opposite of each other on the stems which are pinkish in color and distinctly hairy. Prostrate spurge continually flowers from July to September and produces large quantities of viable seed throughout its life cycle. These flowers are small but numerous, originate from the base of leaves located on the upper-stem, and are composed of several male and female flowers within a cluster. It produces a fruit that consists of a 3-lobed, 3-seeded capsule with stiff hairs on its surface.

Prostrate spurge is very difficult to distinguish from other spurge species, particularly spotted spurge (Euphorbia maculata). In fact, some taxonomists consider the two plants to be the same species. An identifying characteristic of both species is a small reddish-brown splotch at the mid-vein/base of the leaves which acts almost as a camouflage; thus, making the weed difficult to distinguish from the desired turf. The primary difference between these two species is that spotted spurge leaves are often darker in color and the nodes do not produce roots when they come into contact with the soil.

Additionally all spurges exude a milky/white sap when damaged that can be toxic to animals if ingested.

Cultural control: None known specifically for prostrate spurge. Proper turf management such as adequate mowing heights, irrigation, and fertilization will help to produce a dense, aggressive turf which is the greatest defense against invading weeds. Prostrate spurge also thrives in compacted soils; thus, soil cultivation (hollow-tine aeration) may aide in management of the weed. Due to its shallow taproot, prostrate spurge can often be hand pulled when populations are small enough; however, it is important to remove weeds as soon as possible due to its ability to produce copious amounts of viable seed very quickly after germination.

Biological control: None known specifically for prostrate spurge.

Chemical control: Control options for prostrate spurge can include both pre- and postemergence herbicides. Preemergence control can be achieved with spring applications of isoxaben (Gallery, Isoxaben) prior to germination in summer. Dinitroaniline herbicides (such as Barricade, Pendulum) can also be applied for prostrate spurge control though the results are often less consistent than applications of isoxaben.

Once spurge germinates, control in cool-season turf can be achieved with applications of two- or three-way mixtures of 2,4-D, dicamba, MCPP, or MCPA which are available in multiple product formulations at local retailers. Repeat applications may be necessary due to the germination of new seedlings.

For more information on weed control, search this blog and check out our Turfgrass Weed Control for Professionals Publication.

For archives of past weed of the month postings, visit our Weed of the Month Archive.

Aaron Patton, Turfgrass Extension Specialist
Leslie Beck, Postdoctoral Research Associate
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