Monthly Archives: May 2013

May 28th

Hi All,

Spare a thought…

You’ve got to feel sorry for the grass plant at the moment :(….On Friday, it got blasted by cold, northerly winds with a windchill temperature of just 5°C and to add insult to injury, cold rain as well, that dropped the soil temperature down from 13.5°C to under 10°C. Saturday was a gentle reprieve, but for many a slight ground frost started the day…by Sunday, the same, but the wind was picking up and starting to exert an E.T stress, that by Monday had risen to 4mm a day in hot, dry, gale force, southerly / south-westerly winds. So it’s not surprising that it isn’t up to much in terms of greens growth, particularly when we’re cutting low to provide consistency of surface, ho hum 🙁


Haven’t we been here before ?

I have a certain sense of déjà vu typing this blog, particularly when I look at where we were a year ago, jet stream and hence weather-wise. As you can see from the graphic below with the two months placed side-by-side, the jet stream is still prone to slipping south and hence letting cool, wet air follow it. The difference for me is that this year instead of it staying put, it keeps fluctuating from this to a peak and back again, and so we have the scenario described above in terms of wildly fluctuating weather. I know things must be bad weather-wise because I’ve taken to listening to The Verve and Morrisey again ! 🙂


General Weather Situation

Well for this week, we’re in a trough again for most of the week, so that means staying cool and with the ever constant threat of rain, with a lot of places receiving a dollop – 20mm + on Tuesday. Friday looks a better day (hence I’m taking it off) before the weekend slips back again into that trough, but there may be better news round the corner, so read on 🙂

For Wednesday, we still have that Atlantic low pressure in charge so a cool, wet day for some, with that rain band from Tuesday still lingering in a horizontal line (-) from above the Thames Estuary to Wales. Above and below that, it’ll be drier and brighter, but for the south of the U.K, that’ll only last till mid/late morning when that rain band will slowly sink south and give more rain before fizzling out. Ireland should be much better with a sunny day in prospect after the clouds break in the morning 🙂 After lunch, a new front of rain pushes into the north east of England / south-east Scotland and tracks south-west into The Midlands and Wales / South-West England later on in the day to conclude with rain. For Thursday, we have another nice sunny day for Ireland, whilst the dry start in the U.K is temporary with a rain front extending from Edinburgh to Eastbourne (sunshine capital of England apparently, but not this day Andy !) during the day and only the east and west coasts of the U.K staying dry. On the bright side, temperatures will be a bit better for Wednesday and Thursday, reaching mid-teens during the day, and remaining up at night, so that means thumbs up for greens growth (but also disease I’m afraid). Winds will be from the north, peaking on Thursday. Friday sees that trough in the jet stream temporarily dissipate, allowing warmer air across the U.K and Ireland, though the winds will remain from the north. The skies will brighten and by mid-morning, most areas should see the sun, yes, the sun, that’s the yellow thing. Ireland will have a duller day and some light showers, particularly across Leinster. Later on Friday, cloud cover will build again and that may bring some light rain overnight across the north of England and The Midlands, but this should clear on Saturday morning, the first day of June (already!!???) and not a bad day in store for Saturday with hazy sunshine and reasonable temperatures for many, though they’ll be more cloud cover and the risk of light showers across Ireland and Scotland, later in the day. Sunday looks if anything slightly better, particularly for the west and Ireland with more sunshine and nice, pleasant temperatures…smart. Crucially for me, we’ll keep good night temperatures, so that means greens growth should kick off in the latter part of this week.

Weather Outlook

Next week, looks like starting off dry and settled for many with high pressure, yes that’s high pressure (!) building, light westerly winds and temperatures moving up into the 20’s, I think. There’s still a threat of rain towards the end of the week, particularly to Ireland and the west, but at this stage, things look appreciably better for the start of June than they did for the start of May ! Now wouldn’t it be nice to have some dry and settled weather for a change 🙂

Agronomic Notes

Growth-Degree-Day Data and its interpretation

Got the nod on Friday night that the blog and more importantly the GDD data was a subject of discussion (thanks Matt, Claire) on the BIGGA forum and wanted to tackle the subject matter / questions raised whilst it was still fresh in my mind.

The question related to the unit of measurement of growth-degree-days on the vertical axis, as unfortunately in last week’s blog, the graph wasn’t the clearest due to the limitations of the WordPress layout (the software I use to do my blog).

Before I do,  please remember there’s a comment option on each blog that I publish, so you can ask a question, raise an issue, whatever and I do read and answer every one of them. If you prefer to, email me directly, the same comment applies in terms of answering, with the only exceptions being whilst fly fishing, riding my mountain bike or blatting along on my VTR 🙂

Growth-Degree-Days (GDD) are a method of measuring / quantifying the plants growth potential, year-on-year and rose to prominence originally I think in agriculture, but later, they were adapted for turfgrass growth, primarily for the timing of PGR’s with respect to seedhead suppression. An excellent article written by Karl Danneberger on GDD’s is available here who explains GDD’s better than I can, except to say that the model I have created starts on January 1st of each year, (because the grass plant is easily capable of growing in January, as has been shown the last 3 years), is calculated in °C and I use a base air temperature of 6°C for my calculations, as I believe this is required for the initiation of shoot growth on our resident grass species.

GDD’s are calculated using the following formula ;

( (Maximum air temperature + Minimum air temperature) / 2 ) – Base Temperature

(with base temperature fixed at 6°C)

So, if a day has a maximum air temp of 15°C, a minimum of 5°C, and a fixed base temperature of 6°C, the GDD calculation is as follows ;

((15 + 5 ) / 2) – 6   =  (20 / 2) – 6  =  (10) – 6 =  4

As Karl explains, there is no unit for a GDD model, it is simply a number summarising growth potential on any one day and cumulatively, over a given length of time. I’m in the process of trying to link this number with actual growth as measured by clipping yield, but it’s early days yet. So what use is it ?, well it provides a quantifiable measurement of grass growth in a given year for your site and already it has shown me the impact that shade has on this process. In turn you can use it to demonstrate why growth is where it is, i.e slow, normal or flushing.

I can also state that for this year, Poa annua var. annua started seeding in earnest when the cumulative GDD reached 154, which was on the 7th May and Poa annua var. reptans started seeding in earnest when the cumulative GDD reached 191.5, which occurred on the 19th May, nearly 3 weeks later than normal in my books. So GDD data provides a benchmarking model for growth, day to day, month to month and year to year.

Looking at the GDD data for May, we can see what a topsy-turvy month it has been growth-wise, with some distinct peaks and troughs continuing right up to last weekend with a growth check on Friday 24th and Saturday 25th. (low GDD figures)

 Grass growth – The current state of play

The constant ‘stop-start-stop-start’ temperature pattern, so typical of May is causing its usual issues for many on managed turf areas, but I always work on things not really stabilising till the end of May and in particular night temperatures. It is these that are the key to greens growth and I think we will see a gradual pick up as the week goes on and especially from next week. So if you’ve fertilised and nothing much is happening at present, hang fire, before applying on top of the previous application because if you do, you’re likely to get a 2+2=5 growth scenario, if the projected weather stays on track !

Outfield Turf is go !

Just watching the local council guy cut the rec behind my house. I can remember him in April zipping along with scarcely a grass blade flying in the wind, such was the lack of growth back then. Now there’s a bow wave of clippings from his units as he struggles to get on top of the growth !

So if anything I’d be looking to put a PGR + iron mix pretty much top of my list regardless of the type of turf you maintain (golf, sports, etc) because with the rain of this week, gradually increasing soil temperatures (courtesy of those milder nights) and warmer weather on the horizon next week, I think we’re going to see a significant growth flush, particularly on higher-height of cut areas, if it hasn’t already started for you.

“My turf is puffy, slow and unresponsive

With the Poa plant putting a lot of its efforts (and food reserves) into producing seed, the leaf is pale and coarse, puffed up by high soil moisture levels and the sward is soft and slower than usual due to the presence of seedheads.

I got tipped me the nod to an excellent blog (ta Sean) compiled by Golf Course Superintendent – Adam Garr from across the pond at Plum Hollow Country Club, which according to Google Maps (isn’t the Internet great for this kind of thing ???) is located just north west of Detroit, in Michigan State. Adam has put together some great features on specific areas and a couple deal with Poa seedheads (yes they do have them there too you know 🙂 ), click here for an ‘aggressive greens program’ approach to seedheads.

It made me smile, shake my head in awe and feel a bit depressed how far we are behind over here and at the fear of alienating anyone reading this blog, there are so many turf management situations that we deal with on a day-to-day basis, reactively, in fire-fighting mode, which could be prevented by good, practical, cultural maintenance beforehand, if time, money, resource and most importantly, the will and understanding (often from above) is there. The heart of the problem is of course, our poor economic situation, and the plain truth that the threat of revenue loss is king now. Trying to overcome the ‘If it ain’t broke, don’t fix it mentality’ that exists higher up in many circles is hard work…there are exceptions of course, but they are few and far between. (refreshing as they are though when you encounter them)

OK, I’ll get off my soapbox now and deal with the issue that initiated this slight digression. In Adams blog above, he remarks on the loss of 2ft of greens speed due to the onset of Poa annua seedheads and I think the puffier, broader leaf that accompanies them also plays a part in this. High soil moisture levels also promote a thicker leaf and we’ve had plenty of that of late, so all this adds up to slow greens speeds for many and for those maintaining sports pitch scenario’s, the appearance of pale, clumpy grass within the sward.

If the projected weather patterns come about, they will initiate a number of positives to help us manage the above. Firstly, they’ll dry the plant out, so the leaf will fine down, for all grass species that is. Secondly, the growth will allow us to employ some good cultural work, that is verticutting, grooming, brushing, topdressing to begin to manage proactively the mix of grass species present AND get reliable growth / recovery thereafter from our fertiliser regime. Lastly, we’ll be able to control soil moisture levels, firming up greens by utilising targeted hand-watering where it is required. (labour and climate allowing of course)

 Disease Activity

A number of reports of Fusarium doing the rounds, not surprising really with the high soil and leaf moisture levels and when you chuck in some milder nights this week, it could become quite aggressive in places, so be on your guard. Fortunately if we do dry out, that’ll both lower the disease pressure and give us the chance to initiate recovery without having to spray necessarily.

I’ve also seen some Plant Parasitic Nematode (PPN) damage on my travels, which at first glance looks like Fusarium or maybe Anthracnose. (see pic) Both Endoparasitic and Ectoparasitic species are active and the patches tend to show if the sward is at low fertility or has recently suffered a high E.T (Evapotranspiration) event. Ultimately the rub here is to maintain a healthy plant, make sure nutrition is balanced, so not over-fed, nor under-fed. Aeration to generate new roots, unaffected by the PPN’s is also key as will be regular biostimulant applications to suppress plant stress if it does go hot and dry.

Pathogen Complex Effects – PPN + Pathogenic Fungi

One key point pertinent to what we’re seeing at the moment is that it maybe the case that both PPN’s and a disease like Fusarium are active on the grass plant at the same time, working together in a complex. This was first described by Kate Entwistle (no ‘h’ mind) and  Colin Fleming and it’s a bit of a chicken and egg scenario – i.e the PPN weakens the plant and that exaggerates the effect of the plant pathogen …in these cases it means just treating the turf disease (e.g. Fusarium) doesn’t always result in alleviation of the symptoms or recovery is unusually slow. According to Kate, Fusarium and Anthracnose, are the most-often encountered turf diseases that can occur in the presence of a background level of PPN’s…the giveaway that a complex scenario may be at work is that the disease keeps re-occurring in the same location on the turf surface, i.e the same part of a green or a football pitch.

Turf symptoms caused by plant parasitic nematode species and a pathogenic fungi (Fusarium)
















In 9 times out of 10 PPN situations, there’s normally at least one if not two contributory factors (shallow rooting, high E.T days increasing stress, low cutting height, compressed fibre, poor rootzone physical structure, etc) that increase the severity of PPN damage and often dealing with these will also lessen the effect of the nematode, without having to apply a control product. If in doubt, get a sample off and Kate will put you straight :), click here for contact details.

Chafer Activity

A lot of golf courses have seen grub activity this Spring, particularly Leatherjackets, but Badgers, Foxes and Corvids looking for Chafers have also caused significant damage, particularly early in the season when food elsewhere was scarce. For guys managing Chafer Grubs, I’d be interested in any observations of adult Beetles or new juvenile grubs throughout the year, so if you wouldn’t mind, drop me a comment or an email…cheers in anticipation.

Ok that’s all for now, back to the grind…:( or 🙂 as the case maybe

Mark Hunt

May 21st

Hi All,

Another Tuesday blog and unfortunately a premature publishing, so if you got a ‘blind update’ earlier, it was because my blog published just as I started writing it !, ho hum.

May is continuing its up and down weather pattern with North Sea ‘Haar’ exerting a big influence on the temperatures. Haar is a sea fog that drifts inland by convection and typically affects Scotland, the North of England and The Wash areas, but when the wind is in the north-east, it can push well inland. So last week we saw days like Thursday which were ‘Haar-free’ and the temperature shot up to 19°C, but the next day, the Haar moved in, bringing low cloud cover, upping the humidity and temperatures barely broke 12°C.

Speaking of last Thursday, I took a day off to fish Eyebrook reservoir, with my brother and dad to mark the 70th anniversary of the Dambusters raid in WWII. Eyebrook was one of the reservoirs they used to practice on for that famous night raid, flying at just 60ft above the water. So we sat there and witnessed a Lancaster bomber flying at 150ft right over our boat, twice, accompanied by 2 Spitfires and then later, there were 2 low passes by Tornado jetfighters, an absolutely fantastic experience, but it did put the Trout down 🙂

 General Weather Situation

Our weather is still subject to trough patterns as we saw last year, it’s just at the moment they are not lasting for long periods, but coming up we will be slipping into a trough and that’ll introduce cold air down from the north (see image right for Thursday’s temperatures), so not the best forecast for the coming bank holiday I’m afraid, but it shouldn’t be too bad Saturday and Sunday in the U.K.

Tuesday is looking the last day with reasonable temperatures, so after morning drizzle for some, the north of England and Midlands primarily, the outlook is reasonably dry with warm temperatures when and if the sun breaks through the low cloud cover, which may not be until late morning in those areas. Winds will be light / moderate and from the north. Overnight, the cloud cover thickens over all of the U.K and Ireland and this will be thick enough for some light rain coming into Wednesday, which is the change day as that cold air moves into Scotland early in the morning and pushes down, so you’ll notice the colder start to the day up there. Further south, not a bad day, temperatures dropping a little into the low-mid teens and again, a chance of some rain, later in the day, down a central belt of the UK, stretching from the north of England to The Midlands. By Thursday, that cold air has pushed down across the U.K and most of Ireland, so the morning starts cold, with fresh northerly / north-westerly winds and a much chillier feel to the weather in general. The cold air will push rain into Scotland early doors and I expect this to fall as snow over the higher ground, it’ll be that chilly 🙁  That rain will push south across most of the U.K through Thursday morning, but won’t reach the eastern coast of Ireland till the afternoon, so Connacht and Munster should miss most of it. Friday looks a drier, sunnier day, but chilly, with a north-east wind pushing cloud cover off the sea, though there should be some sunny intervals as well. There’s a chance of light rain down the westerly coasts of England and Wales and also potentially heavier rain coming over from the continent for the south-east of England, but as we saw last weekend, rain from the continent is not the most reliable to forecast, one minute its there, the next it isn’t. The bank holiday weekend isn’t looking too bad as the coldest part of the trough pushes away from the U.K, so Saturday and Sunday are looking warmer, we’re talking low-mid-teens, instead of barely double figures prior to that. Saturday looks dry and pleasant with slightly lighter, north winds and hazy sunshine. Overnight into Sunday,  a rain front pushes into west Connacht and Munster and moves eastwards, so a potentially wet day for Ireland on Sunday, but rainfall amounts won’t be heavy. This light rain will push eastwards into Wales and western England introducing more cloud cover later in the day, but further east it’ll be similar to Saturday, so sunny, with cloud cover and temperature’s in the low / mid-teens. Later in the day, there is a threat of rain pushing over from the continent, but as mentioned earlier, this is a tricky one to forecast, so best keep a close eye on your Headland Weathercheck portal for a more accurate forecast closer to the time.

 Weather Outlook

If this rain does push over from the continent later on Sunday, then Monday looks to be unsettled, with showers, especially across the east side of the U.K and a cooler wind to boot, from the east. Further west, the outlook is better, with temperatures picking up a little for the west of the U.K and Ireland, but still with a risk of showers. Looking into next week, I think the outlook is unsettled, with more rain and we’ll be keeping an easterly / then northerly wind direction, so temperatures are likely to be mid-teens at best. Later in the week, high pressure is trying to assert itself, so hopefully warmer and drier for the 2nd part of the week.

Agronomic Notes

Disease Pressure

When you look at this pic from my weather station, taken at 10.21 p.m. last night, it’s not difficult to see why disease has become very aggressive over the last 3-5 days. A temperature of 16.1°C and humidity of 83% is ideal for the rapid development of Fusarium,  I’m getting (and observing) lots of reports of disease outbreaks, so if you think you’re the only one, you’re not. The question is to spray or not to spray and for me that depends on 2 main factors ;

1. – The Poa content of your greens – If it’s high, like most people’s, then the disease threat is also high and …

2. – Looking at the outlook, it’s primarily cool, so the chances of growing it out are not as high as usual for this time of year, particularly as we’re going to get a run of cold nights, so that’ll drop soil temperatures and hence growth potential.

I’m not a fan of spraying indiscriminately through the growing season, (I’ll leave that to the big chemical companies), but taking into consideration the above, I do think the best policy is to spray, either with a light rate contact (Iprodione) mixed with iron or a systemic along the same lines, provided the latter is a good one for controlling Fusarium, so in other words, not a Strobilurin chemistry.

 Nutrition and Growth Potential

If you look at the daily GDD data below, you can see from the profile that it’s up and down like a side profile of The Alps. When we get warm nights, we get a high GDD, when we get colder nights, a low GDD, so that’s what grass growth is like at the moment, up and down, particularly for Poa annua, because it’s putting it’s energies into seed head development currently. Interpreting the GDD data into actual growth levels, i.e clipping yield is the next step for me, to make this data more meaningful, but gut feeling is that you need a GDD figure over 6 to give good growth and you can see we’ve had very little of that over the last 7 weeks.

This growth pattern is quite normal for May in my experience and it’s not usually till the end of this month that soil and night temperatures stabilise and growth patterns become more constant. The problem is every time we get a cold weather trough pushing down, it knocks back growth, great for keeping outfields under control, not great for producing consistent greens.


Two choices here – either stay with low temperature-available granular products or apply low temperature-available foliars, but remember with the latter that these will be less effective if the plant is checked prior to application and / or you get high levels of rainfall just after applying. So if you’re using liquids, I’d tighten the spray frequency down to 14 days maximum, don’t try and stretch things out because it won’t work when we have this type of weather.

Maintaining Uniformity

In my experience Poa isn’t growing consistently at the moment, whereas bentgrass is, so keeping uniformity on a greens surface is challenging. As I’ve said in earlier blogs, a tight cutting height definitely helps to achieve this, certainly <4mm. I know cutting height is a great subject for debate :), but the fact remains, that a lower cut surface provides less chance for the different physical characteristics of the grass species present in your greens to manifest themselves, so that means less bobbling. The plant is not under stress from environmental pressures (heat, drought, etc), but it is seeding, so we have to be mindful of this. Applying Trinexapac-ethyl to greens surfaces is still too early for me, but as always I have an open mind on this, so if anyone’s thinks that they’ve achieved a better surface by applying an early PGR, drop me a line / comment on this blog and I’ll pass on your experience. Outfield turf like tees, approaches, sports fields is another matter, the height of cut is higher, the grass species often different and here applying a PGR makes sense to me at the moment.

Rolling can be also be a good ally during these conditions, just to improve ball roll and take out the bobbling aspect, but you need a firm, (topdressed incorporated / well-integrated into the surface organic matter) surface to get the best out of it. Of course topdressing can help as well, but the tricky part here is that when growth levels are low, it is sometimes difficult to incorporate a good quality, coarse-medium dressing into the surface, without removing it all and compromising the condition of the cutting blade.

So it’s a balancing act, for me, light inputs, applied frequently are the way to go to maintain consistency, so that’s light dressings, light brushing, a tight cutting height and nutrition along the lines I’ve detailed above.

That’s all for now, sorry for the cock-up publishing earlier and I’ll try and get back to my Monday slot in future, but of course next week is a bank holiday here, so we’ll see.

Mark Hunt


May 13th

Hi All,

Bit later in the week than usual I know, but up with the lark at 5 a.m. Monday morning and I was already 2 Costa’s shy to the wind by 9.30 a.m., sitting in the sunshine on the M25, what a rad-man lifestyle I live! didn’t finish this blog post until late on Monday night and didn’t think it sociable to publish it at 11 p.m. so Tuesday morning it is….

Hmmm, the first part of this week looks not great really, as we’re being paid a visit by a cool, Atlantic low pressure system, especially Tuesday and Wednesday, with a chunk of rain on the way for a number of us, though strange as it may seem to some, very welcome in the central and eastern parts of the country, where rainfall has been hard to come by of late… So let’s put some detail on it…

General Weather Situation

Tuesday sees two separate rain fronts pushing into the U.K and Ireland, the first reaches the west coast of Scotland early doors, the second, reaches the south-west of England / Wale, mid-morning and tracks its way diagonally (/) along the M5 towards The Midlands, pushing through to reach the east of England later in the day. The extreme south-east and the area north of say,The Humber, should escape the worst of this rain, but for areas in the firing line, it’s looking like a minimum of 10-12mm is on the cards (more – 50% – for the south-west I’m sorry to say). The rain will be pushed along on westerly winds and they’ll be keeping temperatures down to low double figures through the day. Over night the rain will push into the south-east and east of the country in earnest, so heavy rain for the early hours on Wednesday in these areas . Ireland should miss the worst on Tuesday / Wednesday, pushed along by those westerly winds and instead have a mixture of sunshine and blustery showers. Showery is the picture for Wednesday after that heavier rain clears the east of the country. As skies clear, temperatures will drop on Tuesday and Wednesday night, so a chilly start for many compared to the double-figure nights of late. Thursday will start off dry for Ireland and the UK, but showers will soon bubble up in the west of Ireland and push easterly across the country. The winds though will be much lighter than of later and possibly southerly, though not warm, southerly by any stretch of the imagination. The same weather pattern is true for the U.K with showers bubbling up later in the morning / early afternoon Thursday, but much lighter rain and winds than Tuesday or Wednesday. Friday sees a re-run of Thursday with a showery pattern of weather for Ireland and the U.K, light winds, but remaining cool with low double figure, daytime temperatures. The weekend is looking slightly better, with a dry day in prospect for Saturday, though again there is still a chance of light showers for Ireland, Wales and the west of the U.K p.m. Sunday is looking the reverse with a drier day in prospect for Ireland and the west, but after a dry start for the east, a significant heavy rain front is projected to push across from the continent into the east / south-east of England / The Midlands during Sunday morning and at this stage, it could well bring an 15-25mm of rain to these areas, so not good at all. By the time the rain has reached more central areas, it will give lower, but still significant amounts of rainfall by late morning / early afternoon, so a wet 2nd half of the day here. For the west of the U.K / Ireland, it’ll stay dry most of the day, with no risk of rain, but it’ll still be on the cool side I’m afraid.

Weather Outlook

Still no Unisys solution, but we’re working on it and the GFS models I’m trialing correctly forecast last week’s Bank Holiday weather and the rainfall for Tuesday / Wednesday this week, so all is not lost 🙂 After the potentially heavy rain for some areas on Sunday,  Monday and Tuesday are looking much drier and hopefully temperatures will also pick up in the lighter winds for the early part of the week as a high pressure tries to nudge its way in. At the moment, this looks like stalling after mid-week, so dropping back cool again, but hopefully staying mainly dry. Looking to the very end of next week, we may see that high pressure push in again, so who knows, a nice end to next week ?

Agronomics Notes

Ok, there’s lots to talk about this week, so I’ll try and make it interesting 🙂

Poa seeding

The hot Bank Holiday weather in the U.K (cooler in Ireland I know) triggered the beginning of the Poa seed head flush, but it’s only the beginning because as we can see from this pic, it’s the coarser, annual biotype that’s seeding first, whilst the finer perennial biotype, which produces much less seed heads will follow in due course. If we look at the GDD data from The Oxfordshire, it suggests that the annual biotype began seeding after the cumulative GDD data measured from Jan 1st reached 154. Obviously temperature isn’t the only influencing factor, but this sets a line in the sand, data-wise for the future.

GDD and shade

Now a word of caution, it’s clear from my initial work (ably aided and abetted by the increasingly-proficient Wendy, whose getting a dab hand at crunching this data :)) on GDD data, that there exists great variability from course to course and within 18 greens on a course. If, for instance, you take a tree-lined course, shade plays a bigger part, particularly early in the year when the height of the sun is lower on the horizon. (as this pic shows with the mid-winter path of the sun shown in blue and the early spring path of the sun shown in yellow).

In this scenario, early in the year, because the sun doesn’t clear the tree line, the turf doesn’t warm up as much during the day and consequently drops to a lower temperature at night, so the growth potential is much lower than a more open site. This fact is amply illustrated in the GDD data from 2 sites shown below, the first an open course (minimal shade) sitting at 71m above sea level (asl) vs. a heavily tree-lined course, less than 20 miles away, but crucially also sitting at a greater elevation – 166m asl. Comparing the GDD figures for January, one can see that the tree-lined site had only 25% of the growth potential of the more open site, so when early January was mild, the more open site benefited, whilst the tree lined site did not. The same would be true when you compare greens on the same golf course in an open and shaded perspective.  This has both growth and aeration implications, i.e. you could imagine a scenario where early (January) aeration would work on the open site / greens, but recovery would be much slower on the tree-lined, woodland site / greens.

Soil Temperature / Night Temperature / Growth Potential

You can see why the GDD data is so useful when you look at the graph below of the first 8 days of May. If we just focused on soil temperature alone, you’d say well no great shakes there because it’s pretty consistent over this period, so growth should be as well, but this isn’t the case. If you look at the GDD figures you’ll see that they are pretty low and that’s because the night temperatures were low, so regardless of what the soil temperature reached during the warm part of the day, growth wasn’t forthcoming because of low night temperatures.

You can also see the effect of milder night temperatures on growth potential. On the 8th May, the night temperature was mild (11°C), and the GDD suddenly shoots up to 10.5 and produces a flush of growth on all areas (temporarily).

 E.T / Irrigation Requirement

Those first 8 days of May also highlighted that perennial issue, to water when it is cold at night or not.

Quite simply the logic behind not watering is flawed. If you look at the graph above, on a open site like The Oxfordshire, the total E.T. loss for the first 8 days was 26.4mm and during that same period, only 0.8mm of rain fell, so that leaves a soil moisture deficit of 25.6mm. Working on replacing 60% of that to keep a healthy plant, we would have needed to apply around about 15mm of irrigation over that period. So by not watering, you effectively stop the plant growing, particularly perennial Poa. The argument behind not irrigating with cold water at night is that it will cool the soil down and stop growth. Well you’ve done that anyway because of E.T loss. So the rub is to replace moisture during these periods with light irrigation patterns to wet the top part of the profile, because this is the part that’s drying out. Of course, The Oxfordshire is an extreme example, the E.T loss if high because it’s an open site and the rootzone is USGA-spec, it also doesn’t tend to receive high levels of rainfall. Now your situations will be different, you may have less E.T loss, more rainfall, but remember, by under-irrigating you reduce the soil moisture level to a point where the plant is unable to uptake nutrients, so even if you’ve fertilised, you won’t see the benefit if you’ve under-irrigated / dried the profile down too much.

Nutrition / Spray Windows

If you’re in a situation where you’re still experiencing differential growth and therefore an uneven surface and you want to get things moving, so you can verticut, topdress (and get growth through it) and maybe reduce the cutting height, then for the next 7 days, a low temperature-available, granular fertiliser is the way to go. This is because night and day temperatures will be cool and we’re due for plenty of rain, so granular’s will work best until the weather settles down.

If you’re looking to spray PGR (:)), selective herbicides, etc I’d personally wait till this rain front has moved through and either take a chance towards the end of this week or the beginning of next, after Sundays projected rainfall.

Ok, back to the grind, all the best

Mark Hunt


May 7th

Hi All,

After a beautiful Bank Holiday weekend with temperatures topping 21.5°C on Sunday and Monday here in The Midlands of England (as forecast 2 weeks prior to the event :)), we’re in for a cooler week, particularly from Thursday onwards, as a cold, low pressure system is set to push rain (welcome for most) and noticeably cooler winds into our weather pattern. May started with some pretty cold night temperatures and on the 1st of May I recorded a windchill of -3.8°C at 5.22 a.m., as my weather station shows below. Proves I do get up in the morning sometimes wee Angus! (A long-running bone of contention with a friend of mine who lives under the delusion that only greenkeepers get up early and work long hours 🙂 )

General Weather Situation

Tuesday sees a continuation of Monday’s glorious weather for most, with the only exception to this forecast being south Munster, where a rain front is pushing in for the start of the day and this will move up country through the day to affect Connacht and Leinster, though it may only get as far as Wicklow on the east coast. Elsewhere, save for some rain in the north Highlands and the chance of showers in northern England later, we’re in for another cracking day with light winds and high temperatures. Wednesday sees a cooler start to the day and that heralds the change, as a heavy band of rain pushes into the south west of Ireland and England just after midnight and moves north east affecting most areas through the day with showers, sometimes heavy ones. Temperatures will be down on the highs of the start of the week, but still pretty respectable. By Thursday though, those temperatures have dropped significantly, so a really cold feel to the day and again another band of rain is pushing into Ireland for early morning.  This rain swirls round into the south-west and Wales during Thursday morning and then pushes eastwards across the country affecting all areas through Thursday and particularly across the east coast as it stands now, continuing raining into Friday. This rain will provide cloud cover, so a milder night and as we go through Friday, the winds swing round from the south-west to west and finally north-west, so cool is the order of the day, with temperatures in the low-teens at best. Friday sees more rain showers pushing through Ireland and the U.K on cool north-westerly winds, so a cool, sunshine and showers end to the week. At this stage the weekend is looking better with drier conditions and temperatures recovering slightly to the mid-teens, as the wind swings more westerly, so not bad really for this time of year.

Weather Outlook

Ok, on to our crystal ball gazing….next week looks to start on a mild note, with westerly winds in charge and dry, but by Tuesday / Wednesday, there is a high risk of rain, potentially heavy, pushing in from the west and affecting the southern half of the U.K particularly. By the end of the week, the winds are looking to swing around to the north, so another potential dip in the temperatures on the way, but there’s plenty of time yet for things to change.

Agronomic Notes

Last weeks combination of cold nights, warm days and no rain produced plenty of issues with differential growth in Poa / Bent greens, particularly those that had been aerated, with the grass pushing up in tufts where oxygen was present, but sitting flat and dormant next to it. As discussed last week, there’s definitely a combination of reasons for this differential growth, Poa biotype distribution, nutrition, soil moisture content and organic matter (O.M)  levels. It was pointed out to me (thanks Julian) that the effect is worse on greens where O.M levels are higher and I can definitely concur with this because I’ve seen worse differential growth on higher O.M greens and particularly those that have been aerated. So the key is to keep cutting heights tight (4mm or below), adequate soil moisture, to stop the perennial Poa from going dormant and good nutrition, using a combination of liquids and granular forms. The appearance of the issue is often exasperated by application of granular fertiliser because the growing Poa takes it up preferentially and so you get a dark green blotch, whereas the dormant Poa sitting next to it, with the same granular fertiliser applied, is dormant and not taking up the nutrient.

Growth-Degree Days and Poa seedhead development

This is turning out to be a really interesting exercise and I thank everyone for their data and also Wendy, my assistant, for collating it. So where are this year? (Click on the charts below to download them in PDF format).

Well as you can see we’re a long way back from a ‘normal’ year, if anyone can remember what one of them is like! This means that the grass plant will be in a different growth stage compared to what we would normally expect at this time of year. This has a particular bearing on seed-head development because normally by now we have perennial Poa seeding heavily, whereas I’m only just seeing and getting reports (Thanks John) of the annual seeding. Annual Poa seeding (typically visible on clean-up strips, thin and worn areas) normally precedes perennial (tight, bunch Poa) by 10-14 days, so that would put us up to mid-May for the start of Poa seed-head flush in earnest. These last few warm days will have accelerated the GDD curve somewhat, so hopefully by close monitoring this year, we’ll be able to approximate a GDD total for Poa seeding and thus predict it for the future. (as they do in the States)

An additional factor that has a bearing on this is the very dry spell of weather we find ourselves in, with a wide discrepancy across the country. The South-East got a nice dollop in mid-April, so typically they had 40-50mm of rain in April, with the south-west and Wales, higher than that. In the south Midlands, it’s down to 22mm and for the central Midlands and East, they only received 11mm in April, in total, so extremely dry. If you look at the E.T loss during April of typically 30-45mm, it means in some areas of the country they needed to add 12-18mm of moisture by irrigation to keep things ticking and a lot of people haven’t done that, so there’s another reason why Poa isn’t growing. Of course in the areas where you’ve had plenty of rain, this doesn’t apply.

Got to dash today, so that’s all for now, enjoy the sun and wrap up well for the end of the week!

Mark Hunt