Identification Guide to Landscape Ornamentals with Alternate, Smooth-Edged Leaves

Classification Overview of Landscape Ornamentals

• Grouping Characteristics:

  • Plants in this category possess alternate leaf arrangements along the stem.

  • Leaves feature smooth (entire) or non-toothed leaf margins.

  • The eleven primary ornamental groups in this section include: Oak, Beech, Redbud, Crapemyrtle, Ginkgo, Willow, Holly, Pittosporum, Magnolia, Azalea/Rhododendron, and English Ivy.

• Group Identification Mnemonic:

  • Mnemonic memory phrase: PITTI RED ENGLISH CRAPE GIN AZA HOL WILL BE MAG OAK

Oak (Quercus spp.)

• Foliage Identification Features:

  • Foliage shape is highly variable across different species within the genus, making reliance solely on leaf morphology prone to misidentification.

  • Leaf arrangement follows a distinct spiral down the stem or branch.

  • Each successive leaf along a twig is offset by an angle of $\theta = 72^\circ$ from the preceding leaf.

  • Sighting directly down the longitudinal axis of a branch reveals leaves arranged in $5$ distinct rows.

• Twig and Growing Point Markers:

  • Twigs and active growing points serve as the primary definitive identification characteristic.

  • Terminal twig clusters typically display $5$ distinct buds concentrated at the tip.

• Reproductive Structures (Seeds):

  • Seeds are produced as acorns (nuts), which exhibit substantial variations in overall size and shape.

  • Acorns are formed with a cupule (cap), but mature nuts frequently detach from their caps.

Beech (Fagus spp.)

• Foliage Identification Features:

  • Leaves exhibit prominent, deeply sunken parallel lateral veins.

  • The tissue sections raised between these veins form a undulating surface texture resembling ocean waves.

  • Extension of leaf veins near the margin can occasionally give the leaf edge a subtly textured or pseudo-toothed appearance, though true margins remain smooth.

  • Ornamental cultivars exist in various foliage color forms, including deep red, purple, and variegated varieties.

• Growing Points and Buds:

  • Winter vegetative buds are slender, elongated, imbricate, and sharply pointed.

  • The sharp growing tips exhibit a distinct geometric pattern, often characterized as sharp enough to puncture a soft object.

• Seed Pods and Seeds:

  • Seed pods consist of prickly burrs that split open to release triangular beech nuts.

Redbud (Cercis spp.)

• Stem and Twig Identification:

  • Twigs exhibit a distinct zig-zag structural path between nodes.

  • Stems and branches completely lack thorns or spines.

• Foliage Identification Features:

  • Leaves possess a distinct cordate (heart-shaped) morphology with smooth, non-toothed margins.

• Bud Morphology:

  • Twigs bear two distinct bud types: small, acute vegetative buds and rounded, clustered flower buds.

• Reproductive Structures and Seeds:

  • Produces flattened, papery, legume-type seed pods that hang in clusters.

  • Seeds are small, smooth, oval-shaped, dark brown discs (measuring significantly smaller than a standard United States cent coin).

Crapemyrtle (Lagerstroemia spp.)

• Leaf Arrangement and Venation:

  • Leaf arrangement appears nearly opposite but is technically alternate or sub-opposite/offset: pairs emerge with $2$ leaves on one side of the stem, followed by $2$ leaves offset on the opposite side.

  • Leaf venation is highly distinctive along the mid-rib, forming a curved-edge chevron pattern where side veins curve gracefully near the leaf edge to join adjacent secondary veins.

• Twig Identification Characteristics:

  • Twigs feature a prominent raised longitudinal ridge or wing on the stem directly beneath each leaf node.

• Floral Structures:

  • Individual flowers consist of $6$ crinkled, paper-like petals arranged symmetrically in a circle.

  • Flowers form large terminal inflorescences (panicles).

  • Flower coloration ranges across white, pink, red, and purple.

• Seed Pods and Seeds:

  • Fruit is a spherical capsule divided internally into $6$ distinct seed chambers.

  • Seeds are non-flat and feature a raised, winged ridge along their outer edge.

Ginkgo (Ginkgo biloba)

• Foliage Identification Features:

  • Leaves are broad, fan-shaped, and visually unique.

  • Venation is dichotomous, with all veins originating from a central point at the leaf base and branching outward to the upper margin.

• Fruit and Seed Characteristics:

  • Fruits are borne on pedicels, frequently featuring $2$ stems joined together at the point of attachment.

  • The fleshy outer sarcotesta of the fruit emits a strong, pungent, unpleasant odor when ripe (associated with the phrase "Ginkgo is stink-o").

  • Enclosed seeds (sclerotesta) are smooth, light beige-to-white shells featuring a distinct raised outer ridge.

Willow (Salix spp.)

• Foliage Identification Features:

  • Species exhibit multiple leaf forms; margins range from finely serrate/notched to completely smooth.

  • All varieties feature short leaf petioles.

  • The central mid-vein is raised and prominent on the abaxial (underside) leaf surface.

  • Certain willow species feature enlarged leafy stipules at the junction where the petiole attaches to the branch stem.

• Bud Morphology:

  • Vegetative buds lie appressed (flattened against) the stem in an elongated fashion.

  • Bud tips are rounded to slightly acute with a glossy, shiny exterior cap scale.

• Inflorescence Characteristics:

  • Flowers emerge as dense catkins (pussy willows).

  • An enlarged protective cap or scale is present at the base of each emerging catkin.

Holly (Ilex spp.)

• Foliage Characteristics:

  • Leaves generally present a thick, leathery, glossy, and waxy upper surface.

  • Leaf margins frequently possess sharp, rigid marginal spines, though smooth-margined forms and variegated varieties are common.

• Growing Tips:

  • Growing tips and buds are short, slightly elongated, and exhibit a neat, symmetrical, patterned scale arrangement.

• Fruit Identification Characteristics:

  • Fruit is a berry-like drupe.

  • Drupes are most commonly bright red, but cultivars with white, yellow, or orange fruit are also produced.

Pittosporum (Pittosporum spp.)

• Foliage Identification Features:

  • Leaves are obovate or elongated tear-shaped with a waxy texture.

  • The prominent mid-rib is lighter in color than the surrounding leaf blade and extends approximately $\frac{2}{3}$ of the total distance from the leaf base toward the apex.

• Floral Characteristics:

  • Flowers feature $5$ small petals arranged around a central raised receptacle.

  • Flower colors include white, yellow, or pale red.

• Seed Pods and Seed Morphology:

  • Seed capsules are rounded, $3$-chambered structures ending in a small extended point at the base/apex.

  • Seeds are dark red, irregularly shaped like fine gravel, and coated in a sticky substance.

Magnolia (Magnolia spp.)

• Growing Points and Buds:

  • Terminal growing points feature large, elongated buds.

  • Many species possess buds covered in dense, soft, fuzzy pubescence (recalled by the memory phrase "Maggie has fuzzy feet").

• Foliage Characteristics:

  • Leaves are typically large, thick, leathery, and simple with smooth outer edges.

  • Abaxial surfaces may possess dense, rust-colored or copper pubescence.

• Flower and Seed Pod Architecture:

  • Flowers are large and showy with numerous petals surrounding a prominent central receptacle column.

  • Mature fruit forms a cone-like aggregate cone of follicles.

  • Upon dehiscence, the aggregate fruit opens to reveal glossy, bright red seeds suspended by slender thread-like filaments.

Azalea / Rhododendron (Rhododendron spp.)

• Foliage Morphological Details:

  • Leaf width varies significantly by species: some leaves are widest beyond the midpoint (obovate), while others are widest near the base (ovate or lanceolate).

  • Petioles range from short to moderate length.

  • Leaf tips terminate in a minute, sharp point or mucronate spine.

• Bud Identification:

  • Growing tips resemble those of Camellia species but lack a glossy, waxy surface coating.

• Flower Features:

  • Showy flowers feature $5$ united petals with long, extended stamens.

  • Color variations include pink, red, orange, white, and blue/purple shades.

• Seed Pod and Seed Identification:

  • Seed pods consist of woody, $5$-chambered capsules with rounded tips that open longitudinally.

  • Enclosed seeds are extremely minute, appearing grain-like when evaluated against a standard United States ten-cent coin (dime).

English Ivy (Hedera helix)

• Foliage Dimorphism (Growth Phases):

  • Juvenile plant phase produces palmate, $3$- to $5$-lobed leaves with prominent light-colored veins growing on climbing or trailing vines.

  • Mature adult flowering stems produce unlobed, ovate to heart-shaped leaves with smooth margins.

• Floral and Fruit Characteristics:

  • Inflorescences are arranged in globose umbels borne on mature adult stems.

  • Small yellowish-green flowers mature into spherical, dark blue-to-black berries.