Tree and shrub identification begins as you assess the different parts of the plant and recognize their specific type, color, shape, and size. When these clues are pieced together, you can properly identify the species of the tree, shrub, or plant.
One such clue is the leaf arrangement on the stem, which is formally known as phyllotaxy in botany. There are three basic types of leaf arrangements found in woody trees and shrubs: alternate, opposite, and whorled. For tender plants, you will encounter these types of leaf arrangements: basal, rosette, and distichous.
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Alternate Leaf Arrangement
In an alternate leaf arrangement, there is one leaf per plant node, and they alternate sides.
Examples of trees and shrubs with an alternate leaf arrangement:
- Barberry (Berberis thunbergii)
- Black walnut (Juglans nigra). The black walnut may appear to have an opposite leaf arrangement, but it has compound leaves. The opposite leaflets form the entire true leaf, which alternates on the stem.
- Japanese zelkova (Zelkova serrata)
- Ninebark (Physocarpus opulifolius)
- Smoke bush (Cotinus coggygria)
- Sweetgum (Liquidambar styraciflua)
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Opposite Leaf Arrangement
On these trees and shrubs with opposite arrangement, two leaves arise from the same node on opposite sides of the stem.
Examples of trees and shrubs with an opposite leaf arrangement:
- Ash trees (Fraxinus spp.). The ash tree has a compound leaf, which is also composed of leaflets arranged oppositely.
- Fringe tree (Chionanthus virginicus)
- Maple trees (Acer spp.)
- Olive trees (Olea spp.)
- Viburnums (Viburnum spp.)
A sub-opposite arrangement is a condition in which the leaves are not spaced far enough apart to be considered alternate nor are they perfectly opposite one another.
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Whorled Leaf Arrangement
When a tree or shrub has a whorled leaf arrangement, there are at least three leaves at each node. Some can have both opposite and whorled leaves throughout the plant.
Examples of trees and shrubs with a whorled leaf arrangement:
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Basal Leaf Arrangement
All the leaves arise from the base (crown) of the plant.
Many perennial plants are trimmed back to new basal foliage once the older foliage starts to look tired and worn. Examples of perennials with basal leaf arrangement are:Continue to 5 of 6 below.
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Rosette Leaf Arrangement
When basal leaves are arranged in a dense, radiating cluster, it is considered a rosette leaf arrangement.
Rosettes often referred to as basal rosettes frequently occur in acaulescent plants that have no visible stem. Example leaf arrangements are:
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Distichous Leaf Arrangement
Leaves are arranged in two vertical rows on opposite sides of the stem alternating every 180 degrees. Distichous leaf or botanical element (flowers, seeds) arrangements are a form of alternate leaf arrangement.
Distichous leaf arrangements examples:
- Maize (Zea mays)
- Gladiolus (Gladiolus palustris)
- Giant Reed (Arundo donax)