Leaf Shapes & Phyllotaxy

phyllotaxy

arrangement of leaves on a stem

spiral

• most common

• one leaf at each node

• leaves spiral around stem

distichous

• 1 leaf at eaxh node

• 2 opposite

distichous opposite

opposite pairs of leaves grow at the same node and line up in two flat, vertical rows on exact opposite sides of a stem

distichous alternate

a plant leaf arrangement where single leaves grow at separate nodes along a stem, positioned in two flat, opposite vertical rows on either side

decussate

each successive pair is at 90 degrees to previous pair

whorled

3 or more leaves at each node

oblong

a long, rectangular-shaped leaf with sides that are mostly straight and parallel. It is significantly longer than it is wide, but it curves quickly at both ends to form a rounded base and tip

cordate

a heart-shaped leaf that features a deeply notched base where the stem attaches, and a pointed tip at the opposite end

linear

a long, thin, and very narrow leaf with flat sides that stay parallel from the base all the way to the tip. It looks just like a long strip of ribbon or a blade of grass

acicular

a slender, needle-like leaf. It has a highly compact, cylindrical, or slightly flattened shape that tapers to a sharp, pointed tip

entire

completely smooth and even all the way around the edge, with no teeth, notches, or cuts

toothed

features a jagged edge made of sharp, teeth-like points (like a saw blade). Increases transpiration and photosynthesis early in the growing season, often helping the plant pump out excess water

serrate

teeth resemble a saw blade and point forward toward the leaf tip (apex)

dentate

teeth are more triangular and point outward, perpendicular to the midrib

crenate

edges have shallow, rounded or blunt teeth rather than sharp points

doubly serrate

larger teeth feature smaller secondary teeth along their edges

lobed

feature deep indentations (sinuses) that create distinct sections (__) along the leaf edge without dividing the leaf into separate leaflets

palmately lobed

lobes radiate from a single point at the leaf base, like fingers on a hand

pinnately lobed

lobes are arranged along both sides of a central midrib, like a feather

parted

a deeply indented leaf edge where the cuts go more than halfway to the central midrib or base

palmately parted

deep cuts radiate from one central point

pinnately parted

deep cuts flank both sides of a central vein