The date of onset of leafing of a plantation of 257 related Quercus robur saplings in Dorset, England was studied. The results show predictable temperature dependance when measured against average daily maximum air temperature for the months of February, March and April. The oaks were planted from acorn in 2000 AD, with a common mother. Results show a 50%-leafing on 3 May for 12°C, and an increase of 1°C causing an advance of 5.7 days. Ground frost at River level (19 m ASL) can scorch or kill young leaves. Data collected and processed by

Records of oak leafing

In leaf 2011: Ground frost on 04 May 2011 (4.4°C at 77m ASL) killed some leaves on young oaks. 251 on 04 may 2011 250 on 27 apr 2011 247 on 25 apr 2011 242 on 23 apr 2011 202 on 21 apr 2011 126 on 19 apr 2011 060 on 16 apr 2011 037 on 14 apr 2011 018 on 12 apr 2011 First to leaf was K6 about 06 Apr 11 Last to leaf was J4 on 03 May 11 In leaf 2010: Heavy ground frost on 12 May 2010 (2.8°C at 77 m ASL) killed most leaves on young oaks. 204 on 11 May 2010 195 on 09 May 2010 162 on 07 May 2010 132 on 05 May 2010 104 on 03 May 2010 033 on 28 Apr 2010 First to leaf was K6 about 21 Apr 10 Last to leaf was -- on -- --- 10 In leaf 2009: 255 on 06 May 2009 250 on 04 May 2009 237 on 01 May 2009 199 on 28 Apr 2009 186 on 26 Apr 2009 146 on 24 Apr 2009 086 on 22 Apr 2009 050 on 20 Apr 2009 031 on 18 Apr 2009 009 on 15 Apr 2009 005 on 13 Apr 2009 First to leaf was K6 about 12 Apr 09 Last to leaf was J4 on 12 May 09 Non-MO Q. robur N8 planted 8 May 09 In leaf 2008: 254 on 11 May 2008 252 on 09 May 2008 237 on 07 May 2008 226 on 05 May 2008 131 on 02 May 2008 087 on 30 Apr 2008 070 on 28 Apr 2008 033 on 26 Apr 2008 009 on 23 Apr 2008 003 on 21 Apr 2008 First to leaf was G4 Last to leaf was WG on 14 May 08 Non-MO Q.robur W5 planted 11 May 08 Non-MO Q.robur A2, B8 planted 14 May 08 In leaf 2007: 257 on 01 May 2007 253 on 29 Apr 2007 248 on 27 Apr 2007 232 on 25 Apr 2007 204 on 23 Apr 2007 181 on 21 Apr 2007 149 on 19 Apr 2007 110 on 17 Apr 2007 050 on 15 Apr 2007 014 on 13 Apr 2007 First to leaf was K6. Last to leaf was X2. (It leafed on 3 June.) BBC Springwatch confirms these results. In leaf 2006: 257 on 19 May 2006 255 on 17 May 2006 251 on 15 May 2006 240 on 13 May 2006 217 on 11 May 2006 139 on 09 May 2006 060 on 07 May 2006 030 on 05 May 2006 First to leaf was K6. Last to leaf was X2.

Temperature dependance of leafing. The "50%-leafed" point was chosen, from a sample of 258, and date of occurence graphed against Average daily maximum air temperature over the 3 months (February, March, April) for different years. Results show 12°C=3 May and an increase of 1°C advances leafing by 5.7 days. Data is for 258 Quercus robur (acorns in 2000) in Bear Mead Plantation in Dorset.

Average daily maximum air temperature °C Month 2011 2010 2009 2008 2007 2006 Apr 19.8 15.9 16.3 14.8 19.7 15.2 Mar 13.2 11.3 13.2 11.7 13.3 10.0 Feb 10.8 7.8 9.0 10.8 10.8 7.6 Average 14.7 11.6 12.9 12.4 14.6 10.9 "50%-leafed" dates 2011 2010 2009 2008 2007 2006 20 apr 05 may 24 apr 02 may 18 apr 09 may Late leafers 50%=20apr2011 24apr2009 2may2008 18apr2007 9may2006 A4 dead 4may +10 2may 0 17apr -1 11may +2 I8 dead 1may + 7 7may +5 21apr +3 11may +2 J4 3may +13 6may >12 9may +7 29apr +11 17may +8 K3 dead 28apr + 4 2may 0 21apr +3 11may +2 V5 27apr +7 28apr + 4 2may 0 25apr +7 13may +4 W4 27apr +7 4may +10 7may +5 27apr +9 15may +6 Y1 27apr +7 28apr + 4 7may +5 23apr +5 9may 0

"50%-leafed" date Av.temp Feb-Mar-Apr New leafings per day for different years, showing temperature-dependance of leafing. Collection of this data involves walking 15 miles per year. 20 Apr 2011 14.7°C 5 May 2010 11.6°C                     24 Apr 2009 12.9°C       2 May 2008 12.4°C                    18 Apr 2007 14.6°C     9 May 2006 10.8°C

Compiled, hand coded and copyright © 2008, John Palmer, All Rights Reserved.