From Mighty Oaks?

Oak leaf To my shame, I’m not a plant sci­ent­ist, which means I might be about to ask a silly ques­tion. But maybe not, so here goes.


Every year at this time I col­lect oak (Quercus robur) leaves. We don’t need to go into the reas­ons why (I need the tan­nins), but it’s some­thing I look for­ward to. I love the smell of oak leaves, and for me it marks the turn­ing of the sea­son. Mists and mel­low fruit­ful­ness? Give me a thick car­pet of oak leaves and hazy sun­light every time.

After the rain we had overnight, I popped out this after­noon when the sun came out and made my first col­lect­ing foray of this year. And I noticed some­thing strange. I have favour­ite trees I col­lect from each year because they are con­veni­ent and because they a loc­ated where the leaves tend to be clean and carry little pol­lu­tion. The leaves I have col­lec­ted from these old friends today are the largest I have ever seen. I don’t have any formal data, but in 10 years of doing this, I have never seen leaves of this aver­age size.

My work­ing hypo­thesis is that the high rain­fall dur­ing this year’s grow­ing sea­son is the reason for the large leaf area. Alternatively, I sup­pose it could be pos­sible that low light levels dur­ing the early part of the grow­ing sea­son might have played a part?

So my ques­tion to you, O noble plant sci­ent­ist, is — what’s going on here? And is there any data in the lit­er­at­ure which sup­ports either of these ideas, either in oaks or other species?


AJ Cann. ORCID 0000-0002-9014-3720

Alan Cann is a Senior Lecturer in the School of Biological Sciences at the University of Leicester and formerly Internet Consulting Editor for AoB.

2 Responses

  1. John Runions says:

    Environmental effects, e.g. tem­per­at­ure, rain­fall, abso­lutely play a role in the expres­sion of tree mor­pho­lo­gical char­ac­ter­ist­ics. Often the effect cor­rel­ates with con­di­tions dur­ing the last grow­ing year but in some spe­cies effects can even be cor­rel­ated with con­di­tions dur­ing the past 2 or even 3 grow­ing sea­sons. In this case, the large leaves might res­ult from a com­bin­a­tion of very warm weather two years ago and high rain­fall this year. Another thing to con­sider, has the nutri­ent status of the trees envir­on­ment changed? Did a river flood nearby, or has the area been fer­til­ized somehow?

  2. AJ Cann says:

    No, no flood­ing or fer­til­izers used in this area. Interesting to think this effect could be integ­rat­ing sev­eral sea­sons grow­ing conditions.

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