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.
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.
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!