Part I: Dichotomous Key For Identifying Pine Trees printable pdf download

Part I: Dichotomous Key for Identifying Pine Trees

A dichotomous key is a tool that biologists use to identify organisms like trees, reptiles,

and insects. A key consists of a series of choices that will eventually lead you to the

name of the organism. This key is a “dichotomous” key because for each choice, you

decide which of two options is the most appropriate (from dicho-, meaning ‘divided into

two parts’).

Select your mystery organism and start with the first pair of options in the key. Decide

which choice best describes your organism. At the end of that choice, you will either find

directions about which pair to go to next or the name of the organism. (Warning: there is

one extra plant in the key that you do not have. Be sure to read both choices thoroughly

before you decide which fits your plant the best!)

1a. Plant has seeds in flowers/ fruits and has broad leaves……………….Flowering plant

b. Plant has seeds in cones and has needle-like leaves

….……………………………………………Conifer (cone bearing plant): go to 2

2a. Needles grow individually (not in a bundle) and directly from the branch

………………..……...…………………………Sequoia sempervirens (Redwood)

b. Needles are arranged in a bundle………………...………………….Pine tree: go to 3

3a. (Usually) Three needles per bundle………………………………………….…go to 4

b. Not three needles per bundle………………...…….…...………………………go to 5

4a. Needles 14-25 cm long,……………..…………………………………...……..go to 6

b. Needles mostly less than 12cm long, with three needles per bundle

……………..……................................................Pinus attenuata (Knobcone pine)

5a. Needles are arranged in bundles of five, woody cone does not have a sharp “prickle”

at the tip of each scales…………………………Pinus hartwegii (Hartweg’s pine)

b. Needles are not in bundles of five……………………………………….go to 7

6a. Woody cone (=‘seed cone’*) is very large (> 18 cm long), needles are grayish-blue

and clustered at the end of the branch………………. Pinus sabiniana (Grey pine)

b. Woody cone is 8-12cm long, needles are yellow-green, thin and hang down all along

the branch………………………………….Pinus patula (Mexican weeping pine)

7a. Needles are arranged in bundles of two, woody cone is <5cm and does not have a

sharp “prickle” at the tip of each scale.……...Pinus edulis (Colorado Pinyon pine)

b. Needles are arranged in bundles of two, woody cone is >5cm and has a sharp

“prickle” at the tip of some scales….…………..……..Pinus muricata (Bishop pine)

Part I: Dichotomous Key For Identifying Pine Trees