A late blog as forecast because I took a long Bank Holiday and very relaxing it was although the weather intervened as usual. The mornings started off very cool and windy courtesy of a north east wind pushing Haar in from The North Sea but by lunchtime it was lovely for walking with meadows full of Clover and Buttercups.
Last week I mentioned Pink Campion in my blog only for that horticultural sage, Mike Butler, to correct me and point out that the Campion species we see lining the hedgerows is actually Red Campion (yawn, looks pink to me Mikey ?). Luckily I managed to find a reference to the fact that Red and White Campion (above left) produce a pink hydrid in the wild so I think I was at least half right, genetically speaking..
Go west or north to see some sunshine 🙂
We are experiencing some strange weather at the moment because of that north easterly air stream and currently the U.K is split into three with the central and south east experiencing a very cool and wet spell of weather, the west, lots of sunshine and Scotland, a heatwave.
The rainfall has been unpredictable as well. Last Tuesday just after I had said we were in for a largely dry week (sod’s law), we got some very localised thunderstorms and you can see they worked in a line along the M1 from London. (the image below shows lightning strikes and the time they occurred) I can’t help thinking that it was the heat from the asphalt and cars that triggered off and fueled the storm. I watched the updrafts form right above my house and it went from sunny to dark in a matter of minutes with all the street lights coming on, we then picked up 19mm of rain over a very short period, mega interesting even if the neighbours curtains were flapping a tad as I stood on the front lawn and stared up at the sky for an extended period.
That rainwater contained 0.5kg of nitrogen per hectare by the way for every inch that fell which is kind of normal.(I was hoping for more)
General Weather Situation
So how does what’s left of the week look like ?
As mentioned earlier we have a real split in the weather between the north and west which is currently enjoying fine and warm weather and the central and southern areas of the U.K, which is getting the dirtier end of the stick so to speak. You can clearly see this on the Meteoblue image shown above and it’s a result of the wind direction pulling cool and moist air off The North Sea.
So Wednesday starts off dull and cool for the south and east and in fact they’ll be more in the way of cloud cover for the west again, but the difference will be what happens as we progress through the morning. That cloud spilling in off The North Sea will be heavy enough for some rain across the east / north east and north of England through the morning but further north and west of that cloud bank it’ll be a lovely sunny day with warm periods. By late morning though there’s a risk of showers for the south west, South Wales, Hereford and Worcestershire. For Ireland and Scotland we can expect a clear sunny day with temperatures into the twenties again, whereas further south it’ll be down in the low to mid-teens at best and somewhere in-between for the west. Remaining dull for the south and east then I’m afraid and it’s likely you’ll see some heavy bursts of rain feeding off The Channel into The Home Counties through the morning. The wind will be moderate to breezy under that cloud cover and from the north east, whereas for Scotland it’ll be lighter and more easterly in orientation.
Going through to Thursday we have a very similar picture with perhaps more in the way of breaks in the cloud cover for Wales, the west and south coasts of the U.K through the morning. So warm and sunny for Scotland with maybe a little cloud cover coming through later in the day, dull and cool for the The Midlands and the south east I’m afraid. Later in the day there’s a chance that the cloud may be thick enough for some rain across the south east of England.
Indeed overnight a band of rain is projected to push into the south east and east of England and move slowly westwards so by Friday morning rush hour it’ll be across London and up to The Wash. By late morning it will have reached the East Midlands, central and northern areas, but all the time fading….At the same time we will see thicker cloud push into the east of Scotland and again move westwards to bring rainfall later in the day for eastern and central Scotland. As you’d suspect when the The North Sea is involved, the best weather is furthest away from it so Ireland, Wales and the west of the U.K look to get the best of the sunshine and temperatures. Through the morning that rain will push inland and then fizzle out leaving just thick cloud over the U.K by nightfall, with only Ireland seeing a pleasant enough evening. Temperature-wise, mid-high teens for Ireland, the west and Scotland, but down a couple of degrees for The Midlands, north east and south east of England. The wind will remain north east / easterly in orientation but it should be lighter on Friday.
Looking ahead to the weekend, there is a change on the way in terms of temperatures and wind direction but it won’t be readily apparent on Saturday as we look to have a dull cloudy start for most of the U.K, but brighter for Ireland. During the late morning rain is projected to push in from the east to north, central and southern parts and move into the south and north west later in the day, intensifying as it does so. As this rain moves through it’ll leave behind a sunny and bright end to the day for many. That rain fades away overnight into Sunday to leave a hazy but much warmer start to the day for southerly areas as that wind shifts round to the east and pulls in warm air from the continent. So a warm, bright, sunny day for Sunday is on the cards and you’ll really feel the temperature pushing up in the south with low to mid-twenties on the cards. Further west and north a pretty similar picture with long spells of unbroken sunshine and warm temperatures.
I have to say I haven’t seen a weather picture like this for a long while, it’s a real miss-mash of weak weather systems with no one particular one dominating. We have a jet stream that’s sitting really, really high above us and that should mean we have stable high pressure filling in underneath to give us warm and dry conditions. The fly in the ointment is that we have a low pressure projected to sit out north of The Bay of Biscay from Tuesday onwards and that could easily feed in some rain and it’ll be unpredictable in nature. So it’s a real best-guess looking ahead for everyone and truth be known I think the situation will only become clear as we start next week. So I think we will a dry, warm settled start to the week but there’ll always be a risk of rain, perhaps thunder heading in from the continent to the south east / south of England. This risk increases on Monday night / Tuesday and it may well spill rain as far west as Wales. The most settled weather for the early part of the week will definitely be in the north again I think. By mid-week we have that low pressure projected to pass over us so unsettled for Wednesday before finer, drier weather moves in for Thursday and Friday.
I’d repeat though that I think there’s a good deal of uncertainty with the weather picture for next week due to the potential behaviour of that low pressure system.
Being the start of the month we have a good deal of GDD info to look through…
May 2016 – Thame Location…
May 2016 provided us with the highest amount of growth (according to GDD) since we started monitoring GDD back in 2010 with a total GDD of 208.5 for the month, the previous highest being 198 back in 2012.
As I’ve commented upon in some of my previous May blogs, it has been a typical roller coaster of a month in that respect, so let’s look at it in more detail from a number of locations.
Growth Potential vs. GDD during the summer
From May onwards I start to use Growth Potential as a way of modelling growth more so than GDD and that’s because Growth Potential works on an optimum temperature basis for grass growth and has ‘top out’ functionality within its model. What I mean by that is that if the air temperature gets too hot for grass growth then the figure calculated for Growth Potential will decrease because of how the formula works, whereas GDD will just return a higher and higher figure. That’s the key difference between the two models and because of this, Growth Potential can function as an indicator / predictor of plant stress and that’s key from now onwards.
Here’s how May 2016 mapped out on a daily basis in Wicklow, Bristol, Guildford and York.
The growth flushes are very evident in week 2, 3 and 4 as are the sharp reductions in temperature during the early and mid-part of the month, definitely a roller coaster. You can also see the difference between the locations in terms of total growth across the month.
If you compare the last week of May in Bristol vs. York, it graphically illustrates the west / east divide in terms of temperatures and hence growth. Yesterday for example Bristol was on 0.9 GP, in other words, things were growing well, whereas York was stuck under that North Sea Haar and barely at 0.4 !
You can download the pdf of this content here
Maintenance issues, seeding and disease…
So we know May brought with it some real maintenance issues with huge amounts of grass growth and typically the last one occurred on the run up to The Bank Holiday over here. It was worse in the west where the temperatures were higher however in some places the combination of warm temperatures and a strong drying wind were enough to slow growth naturally due to E.T loss.
Poa annua seeding…
We also know that Poa annua went from little or no seedheads to full-on seedhead expression in less than 5 days at the beginning of the month. It will be interesting therefore to see if that means that the seedhead flush will be shorter this year because the beginning of seeding started so quickly.
Not surprisingly the mixture of sudden increases in temperature and moisture have led to quite a high level of disease pressure during May. Specifically Microdochium nivale in the beginning and end of the month, and Red Thread..
If there is one thing that Red Thread likes it is humidity and there’s been some of that around of late. It also seems to favour the finer-leaved plant species and that includes the latest generation of ryegrass which I think is particularly susceptible to this disease. If you happen to have regulated your grass lately on outfield areas (and you’d have good reason to do so in some areas) it’s likely that you’ll have seen more Red Thread because one of the mechanisms of disease reduction is the physical removal of the mycelium of Red Thread by cutting. Less cutting, less mycelium removal, more disease, simples. It follows of course that if turf is under-nourished and / or growing slowly for another reason, then Red Thread will be more severe. (That’s why all the books recommend fertilisation to remove the disease because you effectively ‘grow it out’ of the sward). Nowadays though I don’t think it’s that simple because I’ve seen aggressive Red Thread on areas that are growing strongly and are being cut regularly.
Looking ahead to the end of this week and the beginning of next we can see a number of features we should be aware of ;
In some areas things will dry out quickly…
Firstly for the south and east of England, you’re likely to experience a growth flush as grass growth approaches optimum over the weekend and early part of next week. Secondly we can see that the projected E.T loss is high over Saturday and Sunday which will mean surfaces will dry out quickly. Interestingly the projected E.T loss for Scotland is 25% higher so for the second week in a row you’ll not only be on the warm side but your turf surfaces will be drying out significantly.
Shallow Rooting = Problems..
This can highlight the presence of plant parasitic nematodes and / or Take-all disease because both of these pathogens attack the roots of the grass plant early in the season, but the symptoms only become expressed when the plant needs to take up high levels of water through its roots. Obviously these roots are already damaged by the activity of the pathogen and so they cannot accomodate the requirements of the plant and we see wilt initially and then leaf loss / symptom expression. If you have higher than normal levels of fibre and therefore more surface rooting then you’ll notice warm temperature / stress first on these areas..
Talking of shallow rooting..
I grew out some cores of Poa annua recently from a golf green in a sand / composted organic matter media and was quite surprised to see how well this ‘shallow rooted, weed grass’ (as it has been termed in some quarters) rooted 🙂 Ok it’s at fairway cutting height but you can see that Poa isn’t always a shallow-rooted grass…
Pale and Pasty
Like most teenagers, a lot of surfaces will look pale and pasty at present because we are still going through the seeding process. During which the plant channels food reserves upwards and away from the older leaves which tend to die off. So the turf surface looks paler because of this and it will thin out more as well because Poa isn’t actively tillering. For me it’s best just to manage the surface culturally and trickle on a little nutrient and iron to help the Poa through as quickly as possible. One things for sure if you put the Poa under stress then it’ll keep seeding for longer…
That’s all for today folks.
All the best