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

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.

Japanese Stiltgrass Control in Turf

Japanese stiltgrass (Microstegium vimineum) is a C4 summer annual grassy weed commonly invasive to forests. It can be problematic in lawns. Often it is problematic in shaded areas adjacent to an infested forest. But we have observed infestations in full sun turfgrass areas where you would normally expect crabgrass to be the predominant summer annual. It seems this weed is becoming increasingly problematic in lawns. But why I am I writing about a summer weed in February?

Japanese stiltgrass in a lawn during late summer.

Japanese stiltgrass is the first summer annual grassy weed to emerge. Preemergence herbicides commonly used to control the summer annual crabgrass (dithiopyr, prodiamine, and pendimethalin) were effective for Japanese stiltgrass control in our research. However, stiltgrass emerges sooner than crabgrass and these preemergence herbicides are only effective when applied before stiltgrass emergence. In our 2022 research we applied these preemergence herbicides on March 11, 2022 in Pittstown, NJ. Stiltgrass typically emerges in March, often about a month before crabgrass. Germination of the seed and subsequent emergence is probably highly variable from year to year and depends on soil surface temperatures. Do not expect seedlings to be killed by frost. While Forsythia full bloom can be used as an indicator to apply crabgrass preemergence herbicides, there is no information available regarding soil temperatures or phenological indicators for stiltgrass emergence.

Japanese stiltgrass seedlings emerged in tall fescue turf in March

Our research found that while preemergence herbicides applied before stiltgrass emergence (in early March) were effective, those same treatments applied around crabgrass emergence in early May were not effective. A mixture of the postemergence herbicide Acclaim Extra (9 fl oz/A) and a preemergence herbicide was effective for stiltgrass control when applied in early May at crabgrass emergence. For stiltgrass control in June, July, and August, higher rates of Acclaim herbicide will be necessary for control. Acclaim Extra is the only product registered for postemergence stiltgrass control in turfgrass. Field research found it to be the most effective control option. See this RCE factsheet for more information about Japanese stiltgrass identification and other control options in non-turf areas.

In summary, to control Japanese stiltgrass, preemergence herbicides need to be applied a month earlier than is typical. If this is not feasible, tank-mixing preemergence herbicide with low rates of Acclaim Extra is an effective option.

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

Green-up Transitioning to Growth: Ready to Mow?

Three weeks ago, many turfgrasses began greening up as surface soil temperatures warmed into the 50s °F during the day. Currently, surface soil temperatures are reaching into the 60s °F during the day, which stimulates vertical leaf growth especially after a rain. Any early spring N fertilization will also encourage vertical leaf growth.

Accordingly, mowing equipment should be reconditioned and ready for routine use. Setup of mowing height should not be overlooked; an incorrect mowing height will lead to problems. Generally, lawn grasses will be easier to maintained at a mowing height of 3-inches or higher.

Grasses will be healthier when there are more leaves (leaf area) to capture sunlight for photosynthesis and shade the soil surface. More photosynthesis helps the grass grow more roots and a shaded soil surface remains cooler. Shade also blocks the exposure of weed seed to light, which is an environmental trigger for weed germination.

Uneven ground is another reason to recommend relatively high mowing. Many lawns are relatively uneven. A lack of smoothness in a lawn contributes to poor mowing.  A mower set 3-inches helps protect high spots in a lawn from being severely scalped. For example, a high spot in a lawn that ends up being cut at 2-inches with a mower set at 3-inches would be cut at 1-inch if the mower were set at 2-inches.

Mower scalp caused by mower deck being set too low on a lawn with uneven ground.


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.

Weed Control in Spring Seedings

The recent warm weather means its time to started on lawn and landscape projects. You may have plans to seed bare spots in the lawn that you didn’t get to in the autumn. These bare spots may be the result of fungal diseases, which were aplenty due to heavy rainfall in 2018. Summer annual weeds such as crabgrass or Japanese stiltgrass can out compete desirable species in the summertime and leave bare areas as well. While autumn is the ideal time to seed lawns in New Jersey, spring seedings can be successful if you have a plan to control summer annual weeds.

Crabgrass in a lawn


Weed competition from summer annual weeds is much more intense and is the main reason spring seedings are unsuccessful. In a mature lawn, you can apply a pre-emergence herbicide (crabgrass preventer) to manage weeds such as crabgrass and stiltgrass. If you recently seeded or have plans to, these crabgrass preventers are not an option.

If you are planning to seed this spring, using a starter fertilizer product that also contains the active ingredient mesotrione is an effective option when applied at seeding. It will control weed seedlings as they emerge without harming the grass you’ve seeded. One product for home lawns that contains mesotrione is Scotts® Turf Builder® Starter® Food for New Grass Plus Weed Preventer. Mesotrione is available for professional applicators as Tenacity® and other trade names. Products that contain siduron (Tupersan) are also an option for crabgrass control at seeding. Mesotrione and tupersan are not as effective as other pre-emergent herbicides such as pendimethalin, dithiopyr, and prodiamine that can be used on mature, well-established lawns.

After mesotrione is applied, weed seedlings and sometimes the turfgrass will appear bleached for 7 to 21 days after the application. The turfgrass will recover but most of the weed seedlings will not. Read the label carefully especially when using mesotrione and seeding fine fescue. Do not over apply mesotrione as it can damage grass you’ve seeded, especially perennial ryegrass. In areas of heavy weed pressure, mesotrione and siduron will likely not provide season-long crabgrass control. A second mesotrione application can be made 4-6 weeks after the initial or post-emergence herbicides that conitain quinclorac or fenoxaprop are also options if crabgrass develops mid-summer. Sprayable products sold for crabgrass control usually contain quinclorac or fenoxaprop.