Well right on schedule my first Hedgehogs conformed to the last one in, first one out principle of life by emerging from hibernation on Friday night. Initially it was the last two of the 2016 brood, but one of their brothers (sisters ?) from an earlier in the year brood has since joined them. Mum and Dad though are still asleep which is par for the course, their old wise heads know that winter isn’t quite finished with yet and so they’re staying tucked up, nice and warm 🙂
As hinted above, our nice little snippet of spring will be coming to a (hopefully) temporary end this week with a cool and a wet interlude as a cold trough system in the jet stream (shown below) settles in to affect our weather. Just to give you something positive to focus on though I think by the weekend we could be warm, dry and settled with lots of sunshine, so get your head down and work through a crappy, cool week and focus on the weekend 🙂
General Weather Situation
So kicking off Monday and we have a wet picture on the rain radar as a thick band of rain sits from south east Munster across the Irish Sea, straddles Wales, The Midlands and pushes up from The Humber to The Borders of Scotland. South of this main rain band it is grey with some light rain around. There is also a band of heavy showers across Connacht, Donegal and these reach across in Scotland. Through the morning on Monday this rain will settle into two bands, one affecting the south of England righ tup to the north, the other affecting Scotland where that rain will fall as sleet and snow at higher altitudes. By lunchtime we also see some more rain pushing into south west Kerry and into south west Munster and this will slowly move north and east through the afternoon / evening to cross and cover Ireland. As the U.K rain sinks south to central and southern England and north across Scotland, it’ll leave a chunk of clear and sunny weather across the north of England so a clear, dry end to the day here. In those clearing skies temperatures will drop overnight and some areas will come close to a ground frost to start Tuesday. Temperature-wise I’d expect Monday to be reasonable with 12°C across the south of England, 10°C across Ireland, Wales and the west and cooler across Scotland with temperatures just tripping 8°C. Wind-wise, they’ll be light to moderate winds and from the west / south west.
Tuesday sees a band of wintry showers stretching down the spine of the U.K overnight and these will be principally affecting the south west of Scotland and Ireland / north west of England as dawn breaks. South and east of this it’ll be a bright but cold start to the day with ground frost in places. Through the course of Tuesday morning that mix of rain, sleet and snow will push across Ireland, the south west of England, Wales, the north west and Central Scotland so very much a west theme for that moisture initially. East and south of this it’ll be a bright but chilly day. Through the afternoon, those showers will push inland into The Midlands and if anything intensify across The South West and Wales unfortunately. That band of rain, sleet and snow across Scotland looks to be set in for the day so it’ll be full waterproofs for me, with a buff and wooly hat I think this week 🙁 A much cooler feel to Tuesday with a stronger westerly wind and as that cold air sinks south I’d expect high single figures to be the order of the day for all areas, so way down on the heights of last week and feeling chilly in that wind despite the sunshine in places.
Wednesday sees that that band of rain and sleet push across from Wales into The Midlands overnight so by dawn we have a large mass of rain and wintry showers across The South West and Central England stretching up the north. Ireland looks to start dry except for some wintry showers affecting Connacht. Scotland should be drier but they’ll still be some wintry showers across central areas and The Highlands. Through Wednesday morning we will see some wintry showers across the west of Ireland, south west / south east of England and the north east of England and Scotland. Between them they’ll be some areas that’ll receive long spells of winter sunshine, I say winter sunshine because it’ll feel right parky under that cloud cover with temperatures barely over mid-single figures in a light to moderate wind. One of the reasons it’ll feel cooler on Wednesday is that the wind will swing round to the north east in most areas pegging back the temperature even further. Closing out Wednesday we still see that rain across the south of England stubbornly in situ over the south east and East Anglia as dusk falls.
Overnight into Thursday we see more wintry showers coming off The North Sea pushed on by that light to moderate, north easterly wind so across the North East of England, down The Humber and Wash Estuaries and across the south east of England, you’ll see a mixture of rain, sleet and snow. With a north easterly wind, the boot is on the other foot for the 2nd part of the week because Ireland and the west of the U.K will be brighter and drier though there is a risk of wintry showers across Leinster first thing. Through Thursday morning we see that mix of sleet and snow sink south and affect an area from the Humber south I think as well as pushing inland into The Midlands. Bright, clear and cold elsewhere. So I’d expect temperatures between 6 – 8°C on Thursday
Finishing off what has been a cool week for all Friday sees a much clearer and drier picture across nearly all of the U.K and Ireland with just some rain and wintry showers affecting north west Scotland. So a much clearer picture for the end of the week, still cool though with that north easterly wind in situ but at least we are dry for 90% of the U.K and Ireland with only those persistent wintry showers spoiling the picture over north west Scotland. Remaining cool but you may just see a gentle lift in the temperatures across Wales and Ireland pushing up into high single / low double figures.
Looking ahead to the weekend we have two key processes at play here and they could conspire to give a very pleasant forecast (which is nice). The first is that the cold trough slinks south and clears the U.K and the second is that a warmer high pressure pushes in from the east. So the weekend looks warmer, dry and settled for most although still with an easterly wind in situ for central and southerly regions. The north and Scotland at the other end of the high will have westerly winds and these will pick things up nicely temperature-wise, so rejoice and enjoy a lovely weekend if it comes to pass. The only fly in the ointment could be across the north west of Scotland where those wintry showers may persist I’m afraid through Saturday / Sunday.
Next week is a tricky one to forecast because although we have high pressure in situ, we also have low pressure sitting in The Bay of Biscay. This is the remnants of the cold low of this week. The key is going to be exactly where the two pressure systems sit in relation to one another from a north / south perspective. At present the low is projected to sit just off the south coast of England and that means it may be close enough to bring some rain to the south of England / South Midlands, The South West, South Wales and South Munster from Tuesday onwards. Otherwise calm and settled with light winds and pretty dry for the U.K with the driest areas the further north you go. Like I say a good deal of uncertainty on this one but I think towards the end of next week we will see a new Atlantic low appear and that’ll shift the winds to the west and bring windier and more unsettled conditions. Mild though with light winds i think on the whole next week, just the rain bit which is hard to call.
A lot to talk about this week because last week’s temperature has really changed the game growth-wise…
Growth Degree Days – Aren’t they useful 🙂
First off, I think it’s good to show you how really useful Growth-Degree-Day models are from a spring growth perspective. So what I’ve done is graphed out the cumulative GDD for the last 4 years, 2014 to 2017 inclusive, from January 1st to the end of March (using projected temperature for 2017 of course as time travel isn’t one of my personal qualities though sometimes I wish it was ! 🙂 ).
I have also put a line in at 100 cumulative GDD because that’s when Poa annua var. annua starts to produce seedheads in my humble opinion…
So let’s look at 2015 vs. 2014 and see how the growth curves matched up…
So you can see that 2014 was a much warmer spring than 2015 and that Poa annua var. annua started seeding on the 21st March, 2014, whereas in 2015, we didn’t reach this point until later in April because we were cooler. Let’s look at this year vs. 2016 for the same location.
We can clearly see that 2017 (in black) has been much warmer so far this year with good growth really from mid-February and some very good growth through early / mid-March.
In terms of Poa annua var annua (that’s the annual version of Poa annua incidentally not the perennial) we can see that it started seeding in earnest on the 10th of March, 2017 and sure enough last week I found Poa annua var. annua seeding (image right) on greens and others areas in the south of England, so I know the model is accurate.
In 2016 at this location we didn’t hit 100GDD cumulative until the 3rd of April, so currently we are tracking 24 days ahead of 2016 in terms of spring growth…
So finally let’s look at the last 4 years graphed over each other…
Hopefully this demonstrates how really useful Growth-Degree-Day models are in providing a quantifiable measurement for grass growth and for using it to predict specific agronomic events like Poa annua seeding.
Perennial Poa Seedhead Development
Staying on the subject of Poa annua seeding, so far I have only talked about the annual biotype of Poa annua rather than the perennial biotype – Poa annua var reptans. To me this biotype begins seeding on or around 180GDD over here in the U.K and a little earlier the more west you are I think. So if the weather pans out as expected over the next 14 days we will hit 180 cumulative GDD some time in early to mid-April in this Watford location and that means the start of the seedhead flush in earnest. That said, this GDD figure will be specific to your location and your perennial Poa biotype, it may be higher or lower GDD-wise, but I think it will be earlier this year.
As a frame of reference, last year we didn’t hit 180GDD at this location until May 2nd !
Last week I predicted that the mild weekend of March 11th, 12th could have kicked off some new Microdochium activity on existing scars but I also wondered if it was mild enough to initiate new infection as well ?
On my travels last week I clearly saw new M.nivale infection as well as new activity on the edge of existing disease scars. I also had some feedback confirming the latter as well (thanks Ian)
So it looks like there is a particular temperature / humidity combination that is required for new M.nivale activity and a different temperature / humidity combination for new activity around existing scars. This is logical as the former schematic would involve a saprophytic fungus becoming pathogenic and the latter, an existing pathogenic population that becomes active again. (What do you reckon Kate on that one ?…now I’ll see how far down she reads :))
Diary of a disease scar…
Now you’ve all seen a disease scar before I know, nothing new in that, but I’ve been following this particular location quite closely so I thought it would be interesting to look at the above and understand more fully what I believe we are looking at. (though I stand to be corrected as usual)
This area received no fungicide over the winter so what you’re looking at is how Microdochium nivale develops over the course of a winter after initial infection which ocurred in this case around the 28th, 29th October, 2016.
It is to me an interesting time lapse of how Microdochium nivale (Fusarium in old language) can develop in a Poa / Bent sward over the autumn winter and I think something we will have to get used to, to a certain extent as we enter a period of less-effective chemicals and more activity. I don’t mean a golf green plastered with scars, more like a low number of scars on susceptible greens.
My greens are purple…
Yes folks it is that time of year again when we see the distinctive purple / red discolouration across golf greens. In brief this is caused by some biotypes of Poa annua photosynthesising during the warmth of the day but once the temperature drops they are unable to translocate those sugars from the leaf. The sugars accumulate and bind to a pigment called Anthocyanin which is a purple / red pigment (the same pigment that we see expressed in the colour of leaves in the autumn) and this becomes the dominant pigment in the grass leaf for a time in place of chlorophyll, the green pigment.
It’s most noticable on greens that are in the open light-wise and so can photosynthesise more during the day. As we reach more consistent day and night temperatures it grows out as chlorophyll once again dominates the grass leaf from a pigment perspective. If you look closely at the affected purple leaf blade and turn it over you’ll notice the purpling is only on the upper side of the leaf because this is the side exposed to the sun.
There’s an article from Peter Dernoeden’s excellent book “Creeping Bentgrass Management” on the net re-printed from Turfax that you can view here.
Ok that’s all for this week, I’ve got a flight to catch and some shirts to iron as well as a tediously long T.T.D list 🙁
All the best.