• Question from:HP

I work in a large suburban office park (southwest Ohio, USA) adjacent to some overgrown, secondary growth woodland on a steep hillside. I noticed today (late April) that the undergrowth (I recognized Osage Orange, as well as other shrubs and some herbaceous plants) were all fully leafed out and green as though it were midsummer. But the taller trees were only just now beginning to put out leaves. Of course, I thought, there'd be selective pressure on the understory plants to put out leaves as early as possible before they are shaded by tallest trees.

But then I noticed that the tallest mature, landscaped trees in the office park, with only lawn beneath them, were all fully leafed out.

Is it possible that the undergrowth plants are doing something (chemicals, maybe?) to delay leaf development in the taller trees? Or is there a difference between the "wild" (well, feral is probably closer) tall trees in the woodland versus the domesticated tall trees in the landscaped areas?

(I wish I could identify some of the taller trees for you, but it was far away, and I can generally only recognize a few species by leaf shape.)

  • University of Wuerzburg, Germany
  • Posts: 9

Hello,
A very interesting question and not that simple to answer. There are several possible explanations.
1) Within a species, individual trees develop leaves consistently early or late; despite strong environmental variation. It therefore is likely due to genetic differences.
2) There is a variation between different species. It is therefore possible that the free-standing tree leaves out earlier because of its species. Species which leave out earlier are normally less affected by cold temperatures in spring or frost.
3) The difference in the understory growth is likely to cause a variation in soil temperature which could cause the difference.
However, I am afraid I am not familiar with the specific vegetation in Ohio and without knowing the species I can not tell you the specific reason for the phenomenon.