Hi All,

Some of you may know I like to try and keep fit (emphasis on the try) and as part of this approach I wear a Garmin Forerunner which amongst many other things keeps a track of your heart rate. I had a laugh last week when I decided to look at my heart rate during a day spent applying trials, trying to keeping alert with copious Costa Flat Whites and finally having the wholely unwelcome sight of a BMW 5-Series Police Car loom up in my car mirrors on a mission 🙁

You can clearly see the effect of all of these actions….


Onto the weather…

So the North-South divide in the weather continues with temperatures hitting 31.5°C here yesterday as I was out for a leisurely stroll and a good 14 days now from the last significant rainfall. We are set to go higher today as hot air from the south pushes into the south of England. Up country we are 15°C cooler in Scotland.  If the weather projections are correct we will move from a peak pattern in the jet stream this week (that has allowed that hot air to push up from Europe) to a trough pattern which will allow cooler, wetter air to push in early next week. (see below)


General Weather Situation

So onto this week and Monday starts for central and southern England as a repeat of yesterday with heat building from the off (already it’s 20°C outside at 6.30 a.m.). Skies are clear right up to The Pennines so it means a hot day for all. Across to Wales and Ireland and we see the same picture, stable high pressure, hot and dry. Further north we see some cloud cover for Scotland which will bring with it some showers and much cooler temperatures, high teens for most areas there. Winds will be light and from the north east. Through the day the temperature builds in the south and may be hot enough to trigger some thunderstorms but it’s no use predicting where and when they will occur.


Thunderstorms begin as an updraft of hot air and this can be initiated off a car park, storage warehouse, ploughed field or the like and so are pretty random. Check the ATD Lightning Detector to see if there’s any storms coming your way in the afternoon / evening here.

Temperature-wise they are saying we could touch mid-thirties in the known hot spots down south which are traditionally Heathrow, Guildford and Gravesend (Keep hydrated Lee and lads :))

Onto Tuesday and we see subtle change in wind direction to the east and this will push some cloud cover off The North Sea into most parts of the U.K, thicker obviously along the east coast. Mercifully this will knock the edge off those high temperatures so we drop to low / mid-twenties for eastern and central locations but across the west, that cloud cover will break and we’ll be back up to the mid-twenties here and across The Irish Sea. For Scotland we see cloud cover remain for most of the day, broken up at times to reveal hazy sunshine. Here we will sit in the high teens for a thoroughly pleasant day. Cloud cover off The North Sea means we will have a mass of cooler air butting up against warmer air and it’s typically this mix that kicks off thunderstorms so there is a heightened risk through Tuesday of this occurring, more I think for eastern, southern and central areas.

This risk of thunder storms extends through Tuesday night into Wednesday morning with a much cooler night hopefully if you receive them. For Wednesday we have an active weather front pushing rain into north Connacht and Donegal through the morning and this rain will make the short hop across The Irish Sea into western Scotland in time for the morning rush hour. It will then push across country through the morning to give a wet day north of the border. For the south and central areas we start off with some cloud cover and risk of thunderstorms but through the course of Wednesday that wind swings round to the south for one last hurrah. This will push those temperatures up again into the high twenties from midday on Wednesday where skies clear and a couple of degrees lower further north where you retain more of that cloud cover. Later on Wednesday evening we could see some of that northern rain push south across the border into northern England. Humid it will be.

Overnight into Thursday and a change to a westerly wind direction will see a front of thick cloud push into Ireland so a much cooler day for you guys across The Irish Sea as that cloud will knock 7-8°C off temperatures, down from the mid-twenties to high teens. So the situation is reversed from earlier in the week with more cloud on western coasts pegging back temperatures into the more pleasant low twenties and that cloud may be thick enough for some mizzly, drizzle across north west England. For Scotland we see a similar pattern, thick cloud, cooler temperatures and some risk of moisture along western coasts. Across central and eastern areas though we will see those temperatures rise again into the mid to high twenties as skies clear and if the forecast is right, this will be the last day of those high temperatures for the southern half of the U.K.

Finishing off the week we see another band of rain and thicker cloud push into north west Ireland and this will move south and east through the course of early Friday morning so you’ll wake up to a much duller and cooler outlook at the end of the week (assuming you get to sleep of course :)) This thick cloud base will bring some rain to the coasts of north west Connacht and Donegal as well as across western coasts of Scotland. It may also bring some drizzle to West Wales and The South West. So a big temperature drop, maybe 10°C less for Friday for central and southern parts as that cloud cover pushes in during the course of the day. That rain affecting Irish coasts will push south and east to cross and cover Ireland by close of play Friday. The rain over Scotland will also push a little further south into north west England later in the day. So we close the week cooler with a fresher, westerly wind in situ.

So how are we looking for the weekend to come, another scorcher or more pleasant ?

Well Saturday could be wet for the north of England and Wales as that band of Irish rain crosses The Irish Sea and moves diagonally south, fizzling out a bit as it does so but it’ll bring some rain to northern England and this may even reach The Midlands later on Saturday. Continuing in the cooler vein from Friday and I for one will be thankful for that 🙂 This rain marks the beginning of the change from high pressure to low pressure and we will see more rain pushing in over Saturday and Sunday, principally more for the north and west (and in particular Ireland) so a much more unsettled outlook for the weekend and cooler to boot.

Weather Outlook

So next week if it pans out as projected that is, is a real about turn with low pressure and a trough system projected to be in place for pretty much the whole week. So a much cooler feel to the weather next week, frequent showers, more north and west initially but as we progress through the week, that low pressure sinks further south and so brings that rain with it to more central areas of the U.K. Potentially very wet for Ireland and the west of Scotland earlier on next week as that low pressure pushes in. I hope the projection is right as we could do with cooling off over here in more ways than one….

Agronomic Notes

I appreciate we have a north-south divide here so some of my comments relating to plant stress levels won’t apply to Scotland but hopefully it’ll be of interest.

During high temperature conditions like this we see the difference in using GDD as a measurement of potential plant growth rates vs. Growth Potential.

Growth Potential has a formula that is calculated on an optimum temperature for growth, in my spreadsheet this is 18°C for a cool season grass. If the temperature pushes above 26°C, we know the growth rate of the grass plant will begin to slow as physiological processes kick in to conserve water and cool the plant. This slowing down of growth rate is reflected in the Growth Potential calculation as a drop in G.P, whereas in the GDD equation we just see a continuation of higher and higher values as the temperature increases. (this is the drawback with using GDD during the summer)

So over the weekend and most of this week we will see a dropping back of Growth Potential and this is indicative of plant stress (see below)


I’ve marked the stress days in red where you can see both a reduction in growth and below that , 4 days of high E.T.

So the upshot is we are in for some hot weather and the prediction is that plant will go under stress.

During such times it is necessary to try and help the grass plant manage these conditions and one of the ways of doing this is light syringing, applying a fine mist onto the grass leaf which will help cool the leaf and reduce moisture loss. It’s the same effect as having a nice shower when it is hot, you come out of the shower and immediately feel cool as heat is taken from the skin to evaporate surface moisture. There are a number of practices that all help the grass plant during what for us is short periods of stress, imagine weeks of this as they get in Southern Europe and The States. (Note temperatures in Spain and Portugal are in the 40’s currently).

Raising cutting height, alternating rolling and cutting, skipping the clean up cut on greens and postponing aggressive aeration all come to the fore during these periods.

There’s a great recent article (June 2017 no less !) in the USGA Record on managing heat stress, some of it is typically American (use of fans which is a must on some of their sites with their pervasive humidity), but a lot of it holds true for us. You can download it here.

Where are you now Toro Hydrojet ?

One of the best machines to use during this time was the Toro Hydrojet because it could vent the greens and inject water at the same time allowing gaseous exchange and cooling of the rootzone. I still see some out there and wonder why they didn’t persist with it because it’s ace in the summer.

Collar Management – Putting Greens

I’ve seen quite a lot of puffy looking collars on my travels and it got me to thinking on this oft-neglected area of the green. These areas typically receive the same level of nutrition as the greens but often are not on the same rootzone, don’t receive the same amount of wear and tear and critically the same aeration.

For these reasons they tend to accumulate thatch and this can present a number of issues.

Not least the potential for disease formation and then ingression onto the green (probably worst with diseases that seem to be able to move like Anthracnose) but also and perhaps more importantly, water movement. If you have a high surface fibre build up on a putting green collar then it will effectively act as a barrier to water movement off the green, holding it in place just in the area that receives twice the cut (the clean up strip).

I have heard it described as ‘Collar Dams’ and for me if you have the resources, it’s worth upping your management of organic matter in collars by aeration and topdessing to reduce organic matter accumulation. You’ll notice the first signs when you see scalping on the collars because the mower has sunk into the surface fibre and the bottom blade has come into contact with the crown of the grass plant. The crown is the area where the plant produces both new shoots and new roots and if it gets damaged, then it’s bye bye grass plant. This situation can become exacerbated by a build up of topdressing on the collars as a result of pulling, matting topdressing off the green so you get a crown effect.

A quick way of alleviating this is to use a turf cutter, strip back the turf, remove the excess sand and level it back. Time-consuming I know but if you can create a healthier environment off green you’ll reduce potential disease infection and increase water movement to give a drier canopy during periods of high rainfall. (Difficult to imagine at present I know)

Plant Pathogens

With a north-south divide in place we also see a split in the types of pathogens present on surfaces at the moment. In the cooler and wetter north (Scotland) we have plenty of disease activity after what has been a prolonged wet spell that we call June..Mostly Microdochium nivale but if I’m right I expect to see the first signs of Anthracnose later this month or early in July following the late May trigger.


In the heat and high E.T of the south and west of the U.K and Ireland, I’d expect to see symptoms typical of root pathogens coming to the fore, namely Take-All and Plant Parasitic Nematodes to name but two. (above are images of Root Gall Nematode in Poa annua greens as an example)

As explained in previous blogs, these pathogens damage the root system of their host species and in so doing reduce the ability of the plant to uptake water. So during hot spells of weather when E.T loss is higher and the plant requires more water just to keep up with this process, it can’t uptake as much as it needs and so shows the symptoms of turf damage.

Kids gloves it is this week in the south from a plant management perspective and I’d be holding fire on PGR, Selective Herbicide apps to outfield until we get to the end of the week if your plant is showing signs of stress. You’ll get poor uptake and in some cases increase the stress on the plant by applying.

For Scotland though you’ll have some good spray days with lower temperatures and some periods of dry weather, especially early on in the week, so I’d make hay whilst the sun shines 🙂

Ok that’s it for this week, short and sweet…like me.

Keep hydrated, slap on the factor 30, don’t forget to top up those bird baths or put a tray of water out for wildlife because those guys need to drink as well you know.

All the best.

Mark Hunt