Rather than using technical botanical terms to describe tree leaves, gardeners and landscape designers tend to use more colloquial terms. A term like "feather-like" potentially carries two meanings. It may refer simply to the structure of the leaf resembling the feather quill, or, in a broader sense, "feather-like" alludes to the fluffy texture of the leaves across the canopy of the tree.
Compound Leaf Structure
A large number of trees display simple leaves -- each leaf blade is undivided, oval or lance shaped and with or without lobes. Other trees have compound leaves, made up of a main leaf stem with multiple blades attached to it. Leaflets that are arranged along a central axis or branches from the axis are called pinnately compound leaves. Pinnately compound leaves most closely resemble the basic structure of a feather. Depending on how large the pinnately compound leaf matures, its visual texture becomes increasingly similar to a fluffy feather plume.
Trees with Feather-like Foliage
The pea or legume family, Fabaceae, contains a huge number of trees that display pinnately compound leaves. It isn't the only plant family with trees producing such foliage, however. Various species grow in temperate or tropical regions and are often used as elegant shade trees. Temperate climate trees with feather-like leaves include black locust, mimosa, honey locust, golden rain tree, sumac, devil's walking stick, black walnut and bald cypress. Feather-leaved tropical trees include jacaranda, royal poinciana, pride of Barbados, copper pod and shower trees. Trees with feathery leaves can be evergreen or deciduous.
While many people like to call palms trees, they are not true trees since they lack cambium and a few other features that hardwood and softwood trees possess. From a conversational or comparative perspective, it's easy to discuss tall, single-trunked palms as trees. Many palms display pinnately compound leaves and are commonly called "feather palms" to distinguish them from other palms that have wide hand-like leaves. Examples of feather-leaved palms include the coconut, parlour, pindo, Alexander, areca, majesty and lipstick palms.
Trees and palms with feather-like foliage are prized by gardeners and landscape designers for several reasons. Rather than a rigid, upright canopy with rigid texture, feather-leaved plants have an air of grace and visual fluffiness. Feathery leaves droop and flop readily in a gentle breeze, adding a romantic feel to a landscape. Feather-leaf trees often don't cast as deep or intense a shade when compared to trees with large, simple leaves.