Conestoga House & Gardens, 1608 Marietta Avenue, Lancaster PA
Probably few large Cottonwoods are in Lancaster County, and with a 2018 trunk circumference (CBH) of 14 feet 3 inches, this tree may be the county’s largest. (The state champ in Halifax is a monster, how- ever: more than 30 feet in circumference.)
"Our Cottonwood," said CH&G caretaker David Kantner, "has cotton only sparsely and not reliably each year. It used to pro- duce more cotton but may have lost a local male companion or perhaps is not flowering very heavily."
The petiole gall seen here (3rd and 4th photos) is Pemphigus, an aphid. These insects overwinter as eggs on Cotton- wood twigs. When the leaves unfurl in the spring, nymphs hatch and feed on the leaf petiole. The tree responds by producing localized growth which becomes the gall; this gall protects the largely immobile nymphs from insect predators and the weather. Eventually the gall splits open and winged adults fly out.
This amazing species (Cottonwood) con- sumes large amounts of water in its growth cycle, as much as 200 gallons a day. If its root is cut, the tree will “bleed” water for days until the wound heals.