Spring Green-up

Rain late last week combined with rising soil temperatures has initiated green-up of some cool-season grasses in central New Jersey.

Spring green-up initiated on a tall fescue lawn.

Spring (March 27, 2023) green-up of a tall fescue turf seeded in the fall of 2022.

Soil temperatures have been slowing increasing over the last few weeks. Currently, the 24-hour and 5-day rolling averages for soil temperature are 47 degrees F at Hort Farm 2 in North Brunswick, New Jersey.

Keep in mind that exposure will influence green-up. Turf grown in shaded locations will remain cooler and hence be much slower to green-up than turf grown in full sun locations. Growth of cool-season grasses will become more vigorous once soil temperatures are consistently above 50 degrees F.

Now is a good time to remove winter debris like branches, twigs, and leaves to avoid smothering damage during green-up of turfed landscapes.

The decision to fertilize a turf/lawn depends on its function and whether vigor or growth needs to be encouraged. For example, a lawn with a full turf cover that is rapidly greening-up should not be fertilized until later this spring; whereas, a lawn that hasn’t fully recovered from last year’s stress damage will likely benefit from a well-timed fertilization with nitrogen. See Rutgers Cooperative Extension bulletin E327, Best Management Practices for Nutrient Management of Turf in New Jersey for more information on fertilization of turf.

Be aware that green-up will vary with the species of grass. Among the cool-season turfgrasses, perennial ryegrass will be the earliest to green-up. Tall fescue will be slower than perennial ryegrass. Green-up of Kentucky bluegrass will depend on the cultivar (variety) being grown; older, common types of Kentucky bluegrass can green-up relatively early in the spring. Whereas, many of the newer, darker green, and lowing-growing types of Kentucky bluegrass can be very slow to green-up. Green-up of a fine-leaf fescue turf will depend on the species; strong creeping red fesuce and Chewings fescue will be faster to green-up than hard fescue.

Zoysiagrass, which is a warm-season grass, will be the slowest to green-up and is not likely to exhibit substantial signs of growth (green-up) until late-May. See Rutgers Cooperative Extension fact sheet FS521, Zoysiagrass Lawns in New Jersey for more information on advantages and disadvantages of growing zoysiagrass.

Property owners with lawns needing repair this spring should select seed blends or mixtures based on site conditions, intended use, expected level of maintenance, and the potential turf quality that can be achieved. See Rutgers Cooperative Extension fact sheet FS684, Turfgrass Seed Selection for Home Lawns for more information.

Mild winter, what does it mean for overseeding of turf or dormant seeding?

Typically, turf management isn’t on top of the to-do list in mid-February. But winter in New Jersey isn’t typical typical this year. The statewide average temperature in January 2023 was 41.0°, which was 9.3° above the 1991–2020 normal and ties with 1932 as the mildest January since records commenced in 1895. For more details on a winter weather recap see the Rutger NJ Weather Network at https://www.njweather.org/

Some may be asking, what does this mean for the overseeding I did last fall to renovate my turf? The answer depends, in part, on what seed mix or blend was used and when was it seeded. The minimum temperatures for seed germination are poorly defined because of the extreme slowness of germination at low temperatures. But observations of late-fall seedings clearly indicate that tall fescue and Kentucky bluegrass seed does not effectively develop a seedling turf once soil temperatures drop to 50° F. Late-fall seedings with fine fescue will also be slow but greater seedling development may be seen with the red fescues (strong creeping red and Chewings). Among the cool season grasses used for turf, perennial ryegrass has the greatest chance for development of turf cover from a late-fall seeding since the species has been observed to germinate at temperatures below 40° F but above freezing.

Because of the mild winter weather, it would be useful to scout any areas of turf that were overseeded last fall to identify and document the extent of seedling emergence and development. This will serve as a benchmark for future assessments and indicators of progress for turf renovation during the approaching spring.

Small seedling plants emerged during winter in a damage lawn.

Although difficult to see, the small seedling plants in this image during February indicate germination and emergence of a late-fall overseeding of Chewings fescue on a lawn that suffered damage from summer stress.

Mild weather may be encouraging some to consider dormant seeding, which is the process of applying seed with the knowledge that it will not germinate (remains dormant) until environmental conditions are favorable for germination later in the spring. For cool-season grasses, that generally means seed will not germinate until soil temperatures are consistently above 50° F. And it is important to understand that air temperature will probably need to be 60° F or above before soil temperatures will be consistently above 50° F. Soil temperature at the 2-inch depth is currently averaging above 40° F at the turfgrass research farm in North Brunswick, NJ.

Dormant seedings have greater risks associated with higher seedling mortality and loss from wash-outs, bird feeding, etc. Mortality can occur if the seed germinates and then a hard frost occurs and kills the seedlings. Losses due to wash-out and bird feeding are greater because proper soil preparation during the winter is limited by excessive soil moisture or frozen conditions dictating that dormant seeding are reliant on frost-action to incorporate seed into the soil. As a result, seed rates for dormant seeding are often increased by 30 to 50 percent as an attempt to offset these possible losses.

When attempting dormant seeding, consider using walk-behind spreaders and other equipment that won’t cause soil damage and compaction. If the soil is dry and firm enough, heavier equipment may be used but dry, firm conditions are often not the case, especially when the soil has frost heaved or rains have saturated the soil. Also, do not add a fertilizer product during winter dormant seeding operations in accordance with sound environmental stewardship. Fertilizers should never be applied to snow-covered or frozen soils as there is a high risk of fertilizer runoff.

If rapid ground cover is a primary goal for dormant seeding, perennial ryegrass will provide the fastest rate of establishment. Also, covering a dormant seeding with a growth blanket will be a great aid to germination and establishment. Growth blankets protect the seed from wash-outs, wind blowing, and bird feeding and retain moisture and heat, thereby accelerating the establishment rate and extending the growing season. Growth blankets also discourage people from trafficking and disturbing the area.

In summary, dormant seedings are much riskier than seeding at more ideal times. This doesn’t mean dormant seeding aren’t or shouldn’t be done, but it does mean expectations need to be tempered based on the associated risks. And it would be wise to have alternate plan ready should the dormant seeding not achieve the expected outcome.

Please Help: Annual Bluegrass Survey

Conditions for good annual bluegrass growth have returned. Whether you adore or despise Poa annua, consider completing a survey which will allow us to collect valuable insights regarding the turf industry and opinions about managing this pesky grass. The results of this survey will inform a national project team of turfgrass weed scientists working to develop improved solutions for annual bluegrass control.

This survey is being conducted to investigate attitudes and actions related to the management of weeds, in U.S. turfgrass operations, including

golf courses,
sports and recreation turfgrass (athletic fields, schools, parks),
sod production, and
turfgrass seed production.

Your participation in this survey is completely voluntary and responses will be anonymous. Please click the link below to begin. The survey may be difficult to navigate on a smartphone device and is best completed on a PC or tablet. Thank you for your time and insight.



Annual bluegrass

Tropical Storm Brings Rain But What About Gray Leaf Spot?

The passing of tropical storm, Fay brought some needed precipitation to the region, albeit too much at once in many places. Relatively dry soils (assumes not being over-irrigated) and the long, warm days of summer should allow turfs to dry out reasonably fast.

But what about gray leaf spot? Spores of the pathogen are thought to be blown up from southern regions to the north on the winds of tropical systems. With the recent passing of Fay, Dr. Bruce Clarke recommends being on the watch for early symptoms and signs of gray leaf spot outbreaks. Gray leaf spot can be severe on older, non-tolerant cultivars of perennial ryegrass while new, improved cultivars will be much less sensitive although not immune. Over the last couple years, we have also experienced some strong outbreaks of gray leaf spot on tall fescue across the region. So don’t ignore the tall fescue turfs if you have some.

For more information, see the fact sheet, Integrated Control of Gray Leaf Spot on Perennial Ryegrass.

Gray leaf spot control with fungicides on perennial ryegrass.

Fungicide plots on a perennial ryegrass cultivar that is highly susceptible to gray leaf spot.

Green-up Started

Soil temperatures have been warming and reached the mid-40s °F last week at Rutgers Hort Farm No. 2 in North Brunswick NJ and are creeping into the upper-40s °F early this week. Dr. Clarke recommends that treatment of turf with a history of take-all patch be initiated when soil temperature averages 40 to 60 °F. Treatment of fairy ring should be initiated when average temperature is in the range of 50 to 55 °F. Waiting to treat beyond these soil temperature thresholds will increase the risk that control strategies are not as effective.

Table 1. Soil Temperature Data under Bentgrass Turf Mowed at 0.375-inch in North Brunswick, NJ on 17 March 2020 at 2:00 PM.

3-inch Depth Thatch-Soil Interface
Current 48 °F 50 °F
24-hour Average 45 °F 44 °F
5-day Average 47 °F 47 °F


Additionally, the Forsythia bloom started last week in central New Jersey, which Dr. Matthew Elmore recommends as a traditional phenological indicator for preemergence herbicide programs on turf.

Initial forsythia bloom in a home lawn in central NJ last week.


Summer Aeration/Cultivation/Venting

Aeration during the summer can be a helpful practice but does need some caution. Many turf managers performing mid-season aeration on putting greens will be using needle tines, which are less disruptive. But the key words are [Read more…]

Glyphosate Alternatives

Recent news about glyphosate has many thinking about alternatives.

Joe Neal (Professor of Weed Science, Extension Specialist & Department Extension Leader Horticultural Science) and Andrew Senesac (Extension Weed Scientist Cornell Cooperative Extension, Suffolk Co., NY) have published a thorough summary of alternatives and the associated pros and cons through NC State Extension at https://content.ces.ncsu.edu/are-there-alternatives-to-glyphosate-for-weed-control-in-landscapes

Roughstalk bluegrass

Roughstalk bluegrass (Poa trivialis) is a cool-season perennial grass often considered a weed. Light green in color it is most obvious in the early spring when it grows more rapidly than other turfgrasses. As temperatures rise in the summer its growth will slow and it often goes semi-dormant until cooler temperatures and rainfall return in the autumn.

A roughstalk bluegrass plant in a lawn in spring.

A small roughstalk bluegrass plant with purple stems.

Infestations usually begin as small plants, but over time these plants spread via stolons and form patches that don’t tend to mix well with other cool-season grasses. These patches form as small plants expand from stoloniferous growth. These stolons (in addition to the lighter green color) can be used to differentiate roughstalk bluegrass from other bluegrasses such as annual bluegrass (no stolons or rhizomes) and Kentucky bluegrass (rhizomes only). Unlike Kentucky bluegrass, roughstalk bluegrass also has a long membranous ligule with a pointed tip.

Patch of roughstalk bluegrass in a lawn.

Patches of lighter green roughstalk bluegrass amongst Kentucky bluegrass

Currently there are no selective herbicides you can use in a home lawn to control roughstalk bluegrass. For many years Velocity herbicide was an option for professional turf managers, but it is no longer being manufactured and is not registered for use in home lawns (golf courses and sod farms only). Xonerate herbicide can provide some suppression, but should be used carefully to prevent injury to desirable turfgrass.

To control roughstalk bluegrass in cool-season lawns and athletic fields, nonselective control with glyphosate (Roundup and others) followed by reseeding is the best option. Apply glyphosate at this time in early spring, before summer stress, for best control. Glyphosate will kill any plant the spray contacts so apply carefully. If the areas are small, consider removing them with a shovel or a sod cutter. Be sure to remove the patch and at least 12 inches of turf surrounding the patch. Removing soil to a 0.5-inch depth should be sufficient to remove the stolons and all growing points. Reseed or sod the area with a desirable turfgrass species after removal.

These recommendations are based off of the 2019 Turfgrass Weed Control for Professionals guide. I highly recommend this guide for professionals managing cool-season turfgrass.

Insane Rain

The summer of 2018 isn’t going away quietly for many in New Jersey. August 2018 will be remembered for a steady dose of torrential rain that has made turfgrass management extremely difficult, especially in the northern half of the state. In the last 30 days, over 12 inches of rain have fallen across several counties in Northern NJ. This is almost triple the 30-year average of approximately 4 inches of rain for this period in a normal year.

These rains have produced saturated soils during an already difficult time of year for cool-season turfgrass (examined by Dr. Murphy in a previous post). High humidity and extended periods of leaf wetness have provided ideal conditions for diseases as well. Desirable turfgrass is thinning out and giving the competitive advantage to certain weeds. If you have weed problems right now you are not alone!

Nutsedge, false-green kyllinga, and creeping bentgrass (where it is a weed in poorly drained areas) are very competitive perennial weeds in wet soils and I’ve noticed they have become more prevalent in recent weeks. Even roughstalk bluegrass has awoken from summer dormancy in some spots.

Amongst annual weeds, crabgrass and goosegrass seem to be especially prevalent this year. Plants that escaped pre-emergence applications matured very rapidly through warm and wet conditions in late July through mid August and made post-emergence control difficult. Crabgrass and goosegrass are much more difficult to control as they mature beyond the 5-7 tiller stage of growth. With heavy rainfall and warm temperatures in late July it was difficult if not impossible to make post-emergence applications in time for optimal weed control.

Goosegrass plant with 4 tillers. Difficult, but not impossible to control.

Goosegrass plant with too many tillers to count. Extremely difficult to selectively control.

In a perfect world, post-emergence herbicide applications are not necessary due to an effective pre-emergence herbicide program. But grass, soils, and weather are not perfect and pre-emergence breakthrough in problem areas is expected. Pre-emergence herbicide programs were pushed to, or past the limit after heavy rainfall this spring. Late May was especially wet in the Central NJ where some areas received almost 10 inches of rain which fell during 11 days of a 17-day period (see CoCoRaHS for statewide maps). These conditions may have increased dissipation of pre-emergence herbicides, especially in sandy soils. Crabgrass breakthrough may be especially evident on slopes, high traffic areas, compacted soils, or where only a single pre-emergence application was made. Research consistently demonstrates that split application pre-emergence programs provide better crabgrass control than a single application and we are seeing history repeat itself in our 2018 crabgrass trials. Split application programs are providing excellent crabgrass control, and two most common pre-emergence herbicides (dithiopyr and prodiamine) are providing the same amount of crabgrass control at both locations. Keep in mind that in our research trials we subject herbicides to intense weed pressure, but the herbicides are applied uniformly under ideal conditions (immediate post-application irrigation, clipping return, non-compact soils) so we can make comparisons amongst treatments. Real world conditions may not be so ideal.

Excellent crabgrass control from a pre-emergence herbicide applied in early April and re-applied mid-June. Notice crabgrass pressure in the non-treated areas around the plot.

Less crabgrass control from a single application of a pre-emergence herbicide in April. In total for the season, the same amount of product was applied to both plots pictured.


Moving forward

Apply post-emergence herbicides if possible. Weed suppression that limits seed production is especially worthwhile on and around high-value sites (e.g., putting greens, athletic fields). Pylex (topramezone) is an excellent option for goosegrass control and crabgrass suppression in cool-season turfgrass. In my experience, applications at 1.0 to 1.5 fl oz/A will control multi-tiller plants (only 0.25 oz/A is permitted in creeping bentgrass). Tank-mixtures of Pylex and SpeedZone also provided excellent goosegrass control in our 2018 research. This tank-mixture will be evaluated more in 2019 as an option in Kentucky bluegrass, perennial ryegrass, and tall fescue. Quinclorac products (Drive XLR8, Solitare, generics) that can be applied at up to 0.75 lbs quinclorac/A are more effective than Pylex on crabgrass in cool-season turfgrass (lower rates can be used in creeping bentgrass) but will not control goosegrass. Tank-mixtures of Drive XLR8 and Pylex are safe to Kentucky bluegrass, tall fescue, and perennial ryegrass in my experience. Acclaim Extra (fenoxaprop) is another good option that will provide multi-tiller crabgrass and goosegrass control at higher rates. See product labels for more information on turfgrass tolerance, tank-mixtures, and weed control efficacy. Be sure to read the label carefully for information on adjuvants. Not including an adjuvant, or using the wrong one will severely reduce the efficacy of many post-emergence herbicides. For even more information, an excellent guide for weed ID and herbicide selection can be found here at the Purdue University Bookstore. I highly recommend this comprehensive guide.

More importantly, use fertilization and cultural practices to encourage recovery of the cool-season turfgrass once temperatures are more favorable and cool-season grasses regain the competitive advantage (hopefully around labor day). A strong stand of turfgrass will be more competitive against winter annual weeds and crabgrass in 2019. Even in cases of severe crabgrass or goosegrass infestation, a total kill of the existing turfgrass stand is usually not necessary if there is a good base of desirable turfgrass lurking beneath the crabgrass. Use selective herbicides, seed, cultural practices, fertilizer, and September weather to your advantage.

Summer Patch on Hard Fescue

Hot weather in early July brought on some severe summer patch (root disease) symptoms in hard fescue. This disease on fine fescues hasn’t been as thoroughly studied as it has been on other grasses.  So recommendations are based on knowledge learned in Kentucky bluegrass (Poa pratensis) and annual bluegrass (Poa annua) turfs. We are establishing plots this summer and fall to learn more about this disease on hard fescue.

Symptoms of summer patch disease on a 4-year-old hard fescue turf in New Brunswick NJ.

Fine fescues are better adapted to dry and infertile soils. Summer performance of fine fescue will generally be better in moderate to light shade than full sun.

To limit damage from summer patch on fine fescues, do not apply more than 2 lbs. of N per 1,000 sq. ft. per year. An acidifying form of N such as ammonium sulfate is thought to be the best choice when fertilizing fine fescues affected by summer patch. Caution is needed when irrigation fine fescue turf, especially on heavy (loamy) soils. Summer patch disease tends to be more severe on soil that retains water. Irrigation should be applied in a manner that moistens the soil after some time of drying but does not keep the soil excessively wet for many days. Mow fine fescue turf no lower than 2.5 to 3 inches and stop mowing when the turf shows symptoms of heat and drought stress in the summer. Fine fescue turf grows more slowly than other cool-season turfgrasses especially when air temperatures approach and exceed 90 °F.

See Dr. Bruce Clarke’s PowerPoint slides for more details on summer patch disease.