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 2012: Leaf count prevented by rain & flooding 2013: Leaf count prevented by wet weather and bad back

Records of oak leafing

In leaf 2015: 240 on 09may2015 236 on 07may2015 209 on 03may2015 179 on 30apr2015 157 on 27apr2015 Half on 25apr2015 130 on 25apr2015 090 on 23apr2015 043 on 21apr2015 028 on 19apr2015 First to leaf was K6 about 13 Apr 2015 Last to leaf was A5 on 09 May 2015 In leaf 2014: 246 on 05may2014 244 on 03may2014 167 on 24apr2014 130 on 21apr2014 Half on 20apr2014 053 on 17apr2014 030 on 14apr2014 First to leaf was K6 on 06 Apr 2014 In leaf 2011: Ground frost on 04 May 2011 (4.4°C at 77m ASL) killed some leaves on young oaks. 251 on 04may2011 250 on 27apr2011 247 on 25apr2011 242 on 23apr2011 202 on 21apr2011 Half on 20apr2011 126 on 19apr2011 060 on 16apr2011 037 on 14apr2011 018 on 12apr2011 First to leaf was K6 about 06 Apr 2011 Last to leaf was J4 on 03 May 2011 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 11may2010 195 on 09may2010 162 on 07may2010 Half on 05may2010 132 on 05may2010 104 on 03may2010 033 on 28apr2010 First to leaf was K6 about 21 Apr 2010 In leaf 2009: 255 on 06may2009 250 on 04may2009 237 on 01may2009 199 on 28apr2009 186 on 26apr2009 Half on 24apr2009 146 on 24apr2009 086 on 22apr2009 050 on 20apr2009 031 on 18apr2009 009 on 15apr2009 005 on 13apr2009 First to leaf was K6 about 12 Apr 2009 Last to leaf was J4 on 12 May 2009 Non-MO Q. robur N8 planted 8 May 2009 In leaf 2008: 254 on 11may2008 252 on 09may2008 237 on 07may2008 226 on 05may2008 Half on 02may2008 131 on 02may2008 087 on 30apr2008 070 on 28apr2008 033 on 26apr2008 009 on 23apr2008 003 on 21apr2008 First to leaf was G4 Last to leaf was WG on 14 May 2008 Non-MO Q.robur W5 planted 11 May 2008 Non-MO Q.robur A2, B8 planted 14 May 08 In leaf 2007: 257 on 01may2007 253 on 29apr2007 248 on 27apr2007 232 on 25apr2007 204 on 23apr2007 181 on 21apr2007 149 on 19apr2007 Half on 18apr2007 110 on 17apr2007 050 on 15apr2007 014 on 13apr2007 First to leaf was K6. Last to leaf was X2. (It leafed on 3 June.) BBC Springwatch confirms this data. In leaf 2006: 257 on 19may2006 255 on 17may2006 251 on 15may2006 240 on 13may2006 217 on 11may2006 Half on 09may2006 139 on 09may2006 060 on 07may2006 030 on 05may2006 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 2015 2014 2013 2012 2011 2010 2009 2008 2007 2006 Apr 15.7 14.8 12.4 14.6 19.8 15.9 16.3 14.8 19.7 15.2 Mar 10.9 12.5 7.6 14.9 13.2 11.3 13.2 11.7 13.3 10.0 Feb 7.4 9.5 6.2 8.6 10.8 7.8 9.0 10.8 10.8 7.6 Average 11.3 12.3 8.7 12.7 14.7 11.6 12.9 12.4 14.6 10.9 "50%-leafed" dates 2015 2014 2013 2012 2011 2010 2009 2008 2007 2006 25apr 21apr ----- ----- 20apr 05may 24apr 02may 18apr 09may Early leafers 8 years | D8 | G4 | K6 | T2 | 7 years | G7 | I6 | L2 | T6 | X7 | Y8 | Zc3 |

"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 (now driving) 15 miles per year. 25 Apr 2015 12.3°C                   21 Apr 2014 12.3°C       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

Early leafers in first batch of the year Total 2015 2014 2011 2010 2009 2008 2007 2006 1 ND 1 A3 1 A7 4 A8 A8 A8 A8 4 B1 B1 B1 B1 2 B8 B8 2 C3 C3 1 C5 2 C6 C6 2 D4 D4 8 D8 D8 D8 D8 D8 D8 D8 D8 3 E3 E3 E3 1 E6 4 F7 F7 F7 F7 2 F8 F8 5 G2 G2 G2 G2 G2 8 G4 G4 G4 G4 G4 G4 G4 G4 7 G7 G7 G7 G7 G7 G7 G7 5 G8 G8 G8 G8 G8 1 H1 1 H5 1 H7 1 I3 7 I6 I6 I6 I6 I6 I6 I6 1 I7 1 J6 1 J7 1 K4 8 K6 K6 K6 K6 K6 K6 K6 K6 1 K7 6 L1 L1 L1 L1 L1 L1 7 L2 L2 L2 L2 L2 L2 L2 1 L4 2 L6 L6 2 M4 M4 1 M7 2 M8 M8 2 N1 N1 2 N7 N7 3 O6 O6 O6 2 P1 P1 2 P8 P8 1 Q3 2 Q6 Q6 2 R2 R2 3 R5 R5 R5 2 R8 R8 2 S2 S2 5 S6 S6 S6 S6 S6 4 S7 S7 S7 S7 1 T1 8 T2 T2 T2 T2 T2 T2 T2 T2 7 T6 T6 T6 T6 T6 T6 T6 1 U1 1 U2 1 U3 2 U6 U6 1 W6 7 X7 X7 X7 X7 X7 X7 X7 1 Y2 2 Y6 Y6 1 Y7 7 Y8 Y8 Y8 Y8 Y8 Y8 Y8 1 Z2 2 Z5 Z5 1 Z6 1 Z7 1 Z8 3 Za4 Za4 Za4 1 Za5 2 Za7 Za7 1 Za8 1 Zb3 1 Zc1 7 Zc3 Zc3 Zc3 Zc3 Zc3 Zc3 Zc3 1 Zc8

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