leaf terminology
Post on 02-May-2023
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LEAF TERMINOLOGY
THE GOAL OF THIS
PRESENTATION IS TO HELP
VISITORS IDENTIFY THE
FLOWERING PLANTS THEY SEE
WHILE HIKING IN THE
WESTCHESTER WILDERNESS
WALK.
TO LEARN HOW TO IDENTIFY
FLOWERING PLANTS YOU WILL
NEED TO LEARN BASIC LEAF
MORPHOLOGY.
IF YOU WISH TO LEARN MORE
ABOUT BOTANICAL TERMS, VISIT
OUR GLOSSAY LINKED FROM THE
FLOWERING PLANTS HOME PAGE
OR, FOR MORE TECHNICAL
TERMINOLOGY, STUDY THE
MANUAL OF LEAF ARCHITECTURE.
A HAND LENS IS ONE OF THE MOST IMPORTANT
TOOLS OF A BOTANIST.
MANY OF THE PLANT CHARACTERS CAN ONLY
BE OBSERVED WELL WITH A HAND LENS.
BASIC LEAF TERMINOLOGY
THE POSITION AND COMPLEXITY
OF PLANT LEAVES ARE TWO OF
THE FIRST CHARACTERS TO LOOK
AT WHEN IDENTIFYING PLANTS.
ALL SPECIES OF MAPLE IN THE
PRESERVE HAVE SIMPLE LEAVES.
IN ADDITION THE LEAVES ARE
ATTACHED OPPOSITE TO ONE
ANOTHER ON THE STEM.
THE ONLY OTHER TREE GENUS
WITH OPPOSITE, SIMPLE LEAVES IS
CORNUS (DOGWOOD) BUT THAT
GENUS HAS ENTIRE, NOT LOBED,
LEAF BLADES.
BLACK OAK GROUP WITH POINTED OR BRISTLED LOBES
Lobing may be variable within a species and sometimes even
within an individual tree
ODDLY (LEFT) AND EVENLY (RIGHT) PINNATE LEAVES
ODDLY PINNATE
LEAVES ARE ALSO
CALLED
IMPARIPINNATE
LEAVES AND EVENLY
PINNATE LEAVES ARE
ALSO CALLED
PARIPINNATE LEAVES.
BIPINNATE LEAF
The entire structure is one leaf,
i.e., everything above the bud
is the leaf. There are no buds
In the axils of the primary and
secondary leaflets.
Always look for buds in the
leaf axils to help you determine
if a leaf is simple or compound.
There are no species with
bipinnately compound leaves
in the WLT Preserve.
Photo by C. Gracie
From Hickey, 1973
LEAF SHAPE,
BASE, APEX, AND
MARGIN CHARACTERS
ARE USED
TO DESCRIBE
FLOWERING PLANTS.
ALTHOUGH THESE
CHARACTERS ARE
USEFUL THEY ARE
VARIABLE AND DIFFICULT
TO DESCRIBE.
SOME SPECIES ARE EASY
TO IDENTIFY WHILE
OTHERS ARE DIFFICULT!
LEAF FEATURES
VENATION ORDERS
There are venation orders greater than tertiary veins but they are not
visible without magnification (see glossary for terms).
TWO DISTINCTIVE VENATION TYPESIn Fagus grandifolia the secondary veins run
straight into the marginal teeth without
branching.
In Acer platanoides the primary veins all come
from the same point.
THERE ARE MANY OTHER
CHARACTERS ASSOCIATED
WITH LEAVES THAT HELP
IDENTIFY SPECIES
THE FOLLOWING SLIDES SHOW
SOME OF THEM
STIPULES OF POTENTILLA SIMPLEX
STIPULES
ARE BRACTS
ATTACHED TO THE
STEM AT THE
NODE WHERE THE
PETIOLE IS
ATTACHED.
THERE ARE TWO
STIPULES AT EACH
NODE.
STIPULES ARE
COMMON IN THE
ROSACEAE AS
SHOWN HERE.
LINEAR STIPULES OF STAPHYLEA TRIFOLIA
THE BLADDER NUT IS THE
ONLY SPECIES IN THE
PRESERVE WITH
PUBESCENT, LINEAR
STIPULES.
Photo by C. Gracie
STIPELS AT THE BASES OF TWO OPPOSITE
LEAFLETS
STIPELS OF
SAMBUCUS
CANADENSIS (THE
COMMON
ELDERBERRY).
STIPULES ARE FOUND
AT THE BASES OF
LEAVES WHEREAS
STIPELS ARE
LOCATED AT THE
BASES OF LEAFLETS.
STIPELS ARE ONLY
FOUND ON SPECIES
WITH COMPOUND
LEAVES.
PETIOLAR GLANDS OF PRUNUS SEROTINA
THE BLACK CHERRY IS
EASY TO IDENTIFY
BECAUSE IT HAS:
ALTERNATE, SIMPLE
LEAVES WITH SERRATE
MARGINS AND GLANDS AT
THE APEX OF SOME OF THE
PETIOLES.
THE GLANDS ARE NOT
APPARENT ON EVERY
PETIOLE SO LOOK AT
SEVERAL LEAVES. THEY
ARE ALSO MORE DIFFICULT
TO FIND ON OLDER
LEAVES.
STIPULAR-DERIVED TENDRILS OF SMILAX ROTUNDIFOLIA
THE CATBRIER IS
THE ONLY SPECIES
IN THE WLT
PRESERVE THAT
POSSESSES
STIPULAR-DERIVED
TENDRILS.
Photo by C. Gracie
GLANDULAR LEAF
PUNCTATIONS OF
SAINT JOHN’S-WORT
TO SEE THE PUNCTATIONS
VIEW THE LEAF AGAINST
THE SKY THROUGH A 10X
HAND LENS
LEAF PUNCTATIONS OF HYPERICUM PUNCTATUM
Photo by C. Gracie
TUFTS OF TRICHOMES IN THE AXILS OF SECONDARY VEINS
OF THE AMERICAN BASSWOOD (TILIA AMERICANA)
Photo by C. Gracie
STEMS ALSO HAVE CHARACTERS THAT HELP
IDENTIFY SPECIES
THE BURNING BUSH
(EUONYMUS
ALATUS) HAS
GREEN STEMS WITH
REDDISH-BROWN
WINGS. THESE
CHARACTERS MAKE
THIS SPECIES EASY
TO IDENTIFY. STEMS
LIKE THIS ARE
CALLED ALATE
(WINGED).
THE BURNING BUSH
IS A COMMON
INVASIVE PLANT IN
THE WLT PRESERVE.
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