15 Most Invasive Trees in the World

The Invasive Species Specialist Group (ISSG) has recently published a report on the world´s worst 100 invasive species.  Of the 100 species listed there are 15 tree species. 

• African tulip tree (Spathodea campanulata)
• Black wattle  (Acacia mearnsii)  close cousin in to the Silver wattle (A. dealbata)
• Brazilian pepper tree  (Schinus terebinthifolius)
• Cluster pine  (Pinus pinaster)
• Erect prickly pear  (Opuntia stricta)
• Fire tree  (Myrica faya)
• leucaena  (Leucaena leucocephala)
• melaleuca  (Melaleuca quinquenervia)
• mesquite  (Prosopis glandulosa)
• Giant Sensitive tree  (Mimosa pigra)
•  privet  (Ligustrum  robustum)
• pumpwood  (Cecropia peltata)
• Quinine tree  (Cinchona pubescens)
• Shuebutton ardisia  (Ardisia elliptica)
• Strawberry guava  (Psidium cattleianum)
• tamarisk  (Tamarix ramosissima) 

Source...
http://www.issg.org/publications.htm#worst100

100 of the World's Worst Invasive Alien Species
Lowe S. J., M. Browne and S. Boudjelas (2000)
Published by the IUCN/SSC Invasive Species Specialist Group (ISSG),
Auckland, New Zealand.

Some images of the these trees (or their close cousins)

(African tulip tree)

(Wattle)

(Brazilian pepper tree)

(Prickly Pear)

(leucaena)

(Tamarisk)

Types of Inflorescence

An "inflorescence" is a cluster of flowers arranged on a branched stem structure.  There are a number of distinct types of inflorescence.  I´ve included ten basic ones here although there are additional ones that are variants of some of the ones shown in the image below.  The types of inflorescence that I have included in the graphic are

1.  Solitary
2. Spike
3. Spadix
4. Raceme
5. Cyme
6. Umbel
7. Compound umbel
8. Corymb
9. Panicle
10. Capitulum

I do not know for sure whether or not all of these diverse flower forms are found on trees.  Given the many species of trees in the world I think that it is likely.  some of these forms however may be much more common in smaller plants.

Sweet Chestnut tree in full bloom

I came across this beautiful Sweet chestnut tree in full flower in Portland.  This is the tree species that edible chestnuts come from and one good way to tell this tree apart from the non edible Horse Chestnut is by its flowers.