I was going to call this quiz a ‘stumper’ but that would have been a giveaway – not to mention a horrible pun! This is a sycmore (Platanus occidentalis) and, as noted by a couple of folks, the large size is due to being produced by stump sprouts. Now I know why Linda says this is such a good class!
Ok, I’ll admit my ignorance. Why do the stumps produce such large leaves?
Stump sprouts, water sprouts, and suckers are forms of adventitious shoots (shoots that arise some where other than an apical bud). These are often fast growing-shoots with larger than normal leaves. Why? Probably several factors; but certainly a combination of ready access to a reserve of carbohydrates in the roots and an interuption of normal hormornal balance play a major role.