Leaves - Shape Part 1

what they really are. If they are truly separate leaves, you'll generally - on plants from temperate climates - find a bud at the leaf axil (where the leaf attaches to the stem). If there aren't any buds, you're looking at a true compound leaf.

Stem Arrangements

The way in which leaves are arranged on plant stems is not really related to shape, since leaves of just about any shape can be arranged on a stem in any way. How they are arranged, however, helps us to identify different plants.

alternate = leaves in alternate steps along the stem with only one leaf at each node
opposite = leaves across from each along the stem; two leaves at each node
whorled = leaves in circles along the stem
rosulate = basal leaves form a rosette around the stem; very short nodes.

Variations

There are leaves that don't look at all like what most of us think of as leaves.

bract The most leaf like modification . When they look like leaves, what sets them apart is that they are often not the same shape as the other leaves on the plant. Quite a few plants have bracts that we think of as flowers, Cornus florida, the native dogwood, for example.
Tendrils are another that you'd never think was actually a modified leaf.
Scales are also modified leaves and can occur on buds, bulbs and rhizomes.
prickles and some thorns are really modified leaves...strange but true...including the spines on cacti.
Carnivorous (actually, I think, more correctly called "insectivorous") plants develop leaves modified for catching and digesting insects, which is how they obtain nitrogen in the nutrient poor soils in which they grow. Pictured is one of my loves, Sarracenia, the pitcher plant. Not for shade, but if you've got a sunny spot for a bit of a bog, they are incredible.

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