What is a leaf?


A leaf is the main organ attached to the stem.  It is specialized for photosynthesis. Over time, it has evolved into a plethora of different shapes, sizes and characteristics. These vary considerably depending largely on their adaptation to climate.

Leaves have also adapted to the available sunlight, presence of grazing animals, available nutrients, and competition from other plants. Taxonomists use all these different characteristics to classify plants – and every characteristic has a specific name.

Beware – this name giving thing is daunting!

Typical leaf


Parts of a leaf


Leaves and stems together are called “shoots”.  We call both together “foliage”.  A leaf blade is called “lamina” . The top side is “adaxial”, lower is “abaxial”.  Broad flat leaves are known as “megaphylls” (Hosta).  Plants with small leaves – “microphylls” (Boxwood).






Leaves attached to stems by stalks (petioles) are called “petiolate” (Birch).  Those that have no attachment, or if attached directly – “sessile” (Iris).

A petiolate leaf


Sessile leaves


Leaf Margins


A few common (but not all !) names of leaf margins


Arrangement on the stem


The most common arrangement of the leaf on the stem is either “alternate” (Sweetgum), or “opposite” (Maple).  Less common are “basal”, “cauline”, “verticillate”, “rosulate”, or “in rows”.


Leaf shapes


The blade (lamina) can be “simple” (Hibiscus) or “compound” (Rose).  Compound leaves are further broken into “palmately compound”, “pinnately compound, “odd pinnate”, “even pinnate”, “bi pinnately compound”, “trifoliate”, or “pinnatifid”. Take a look at all the leaf shape classification in the table below !


Common names of leaf shapes

And yes – I did study all of these names when taking my Taxonomy classes !


More Classifications


Specific names exist for particular shapes of petioles.  Also for leaf margins, leaf venation, how pronounced is the venation, the shape of leaf tips, the shape of the base of the leaf, or the surface of leaf.  Even how hairy, or if it’s a young or old leaf !

OMG ! 

So many classifications !


My classification of this Begonia rex leaf is “pretty” what about you !


So don’t worry if your gardener tells you your tree has Palinactodromous leaves


– it just means the leaf veins branch beyond the primary split – all good!


Call Plant Specialists today and have us put some leaves in your garden.

( with the plants of course! )

Don’t delay – the sooner the better !







Article written by our Staff Horticulturist, Peter B Morris, BSc, MSc, MBA

All photographs used with permission @SHUTTERSTOCK