Chapter 1 plant identification.
A plant may be identified in many ways. Most often a plant is identified by characteristics of its leaves, but it is also possible to identify a plant by its flowers, fruit, bark, twigs, buds, or habit of growth. The process of identification can range from very simple to complex. For example, the identification of most familiar Oak trees is simple during the warm season when the leaves are present; however, identification becomes very complex during the winter season when the leaves are gone. At that time, one must rely on minute details of buds or leaf scars, minor bark characteristics, and other clues. This text will not address every detail, but, rather, it will emphasize the major characteristics used in identification, as well as those features that make a plant a good choice for landscaping purposes.
When one learns a new plant, one must associate a name with the plant in order to file the plant into memory and be able to communicate effectively with others about the particular plant. Plant names may be grouped into two categories--common names and botanical names.
Common names are those names people of an area give to a plant. Common names of plants can evolve in different ways, just as the names of towns, rivers, roads, and other landmarks evolve over a period of time. Our first experiences with plant names are common names. One advantage to such names is that they are usually easy to remember. Names such as Sugar Maple, White Oak, and Sweetgum are common names with which many people are familiar. The major disadvantage is that common names often vary from one location to another. For example, the names Liriope, Lirio, Lilyturf, and Monkeygrass can all refer to the same plant. This can be confusing and frustrating when communicating with others, since there are no world-wide standards that govern common names. In fact, you could develop your own common names--many people do.
Botanical names, or scientific names for plants, help to eliminate confusion in the plant kingdom. A disadvantage for the beginning gardener or student of horticulture is that botanical names are written in Latin and are sometimes difficult to remember, especially at first. Latin is the standardized language of scientists worldwide. Cercis canadensis is the botanical name for the Eastern Redbud anywhere in the world, regardless of what it is commonly called in a particular location.
The binomial system or two-name system developed by Carolus Linnaeus in 1753, is a system that allows botanical names to be written using the genus and species names. Often, a third name is included after the species name to indicate a variety or cultivar within the species. This system assures that no two plants will have the exact same botanical name. This eliminates much confusion, and it gives all who work with plants a common language.
Genus. The first word in a botanical name is the genus. A genus is a group of plants having more common characteristics than with plants of any other group. Sometimes only one major characteristic may determine the genus. For example, all Oaks belong to the genus Quercus and have many common characteristics. One major characteristic of Oaks is that they produce nut-like fruits called acorns. A genus name begins with a capital letter, and is either underlined or italicized.
Species. The second word of a botanical name is the species. The species is the name given to a group of similar plants within a genus that have common differences with other groups of the same genus. When a new genus is discovered, a species name is assigned that identifies some characteristic of the plant. As different plants are discovered within the genus, new species names are assigned to those groups. Some genera have many species. For instance, the Oaks (Quercus) have many species such as Quercus alba (White Oak), Quercus stellata (Post Oak), Quercus palustris (Pin Oak), and so on. Species names are written in lower case and either italicized or underlined.
Very often in landscape plants, a third name appears after the species name. This third name will identify a particular variety, sometimes thought of as a subspecies, or it may identify a cultivar (cultivated variety). The variety or cultivar name is especially important in modern landscape work, since thousands exist. The list grows larger each year. An understanding of the differences between a true variety and a cultivar will help the individual interested in landscaping to understand important characteristics of various plants.
Variety. A true variety is a form of a certain species that varies from the established species in one or more characteristics. The characteristics are passed on with a high degree of purity or certainty when the plant is reproduced by seed (sexual reproduction). Some varieties produce 80 or 90 percent purity from seed. To assure absolute purity, the variety is usually propagated by cuttings, budding, grafting, or tissue culture (asexual propagation).
The true variety is written in Latin using lower case letters and underlined, or italicized. An example of a true variety is the Red Japanese Barberry. It varies from the species by having red leaves as opposed to the green leaves of the species. The variety name can be written in one of two forms as follows:
Berberis thunbergii var. atropurpurea
Berberis thunbergii atropurpurea
Cultivar. A cultivar, or cultivated variety, is a variety that will not reproduce purely from seed over several generations. A cultivar originates as a "sport" (mutation), or as a result of crossbreeding or cross-pollination. It is usually produced by asexual means such as cutting, budding, grafting, or tissue culture. Often, a cultivar is discovered by an individual who secures a plant patent for exclusive rights to reproduce and sell the plant. There are many patented plants available in the nursery industry. A patented plant that proves very popular can result in much profit to the individual holding the patent. A cultivar may be written in Latin, or it may be named in any language at the option of the person who first discovers it. The name of a cultivar that originates as a mutation is enclosed in single quotes, but it is not underlined or italicized. An example of a cultivar of this type is the October Glory Maple. It is written as:
Acer rubrum 'October Glory'
Acer rubrum cv. October Glory
Varieties and cultivars that are the result of crossbreeding are written somewhat differently. A cross or hybrid between two species is given a Latin name if it is a new species, or a proper name if it is a cultivar. In either case, an x is substituted for the species name. Latin names are italicized or underlined. Proper names of hybrid cultivars are enclosed in single quotes and capitalized.
Glossy Abelia was developed as a cross between Abelia chinensis and Abelia uniflora. It is written as:
Abelia x grandiflora
Emily Bruner Holly is a result of a cross between Ilex latifolia and Ilex cornuta. It is written as:
Ilex x 'Emily Bruner'
As one works with botanical names, they become easier to remember, and new names are learned at a faster rate. In addition, common names of some plants are identical to the genus name. No one knows all botanical names. The beginner should acquire lists, references, and other materials that contain both common and botanical names. When writing plant names, always include the appropriate botanical name as a second name. Over a period of years, beginners will find that they can associate many botanical names with common names. Eventually, they can take great pride in using botanical names.
The orderly classification of plants based on relationships and differences is called taxonomy. Taxonomy takes into account the various parts of a plant as well as its color and shape. It is possible to identify almost all plants from above-ground parts, although roots and below-ground parts vary. For instance, a Sweetgum tree has a taproot system, but it is easily identified by its leaves and stem characteristics.
It is important to have access to reference material on the terminology used by taxonomists in describing plant characteristics. The drawings and explanations contained in this text should prove helpful; however, the usefulness of the material as a reference is more important than any attempt at memorization.
The leaves of a plant are used extensively in the identification of plants as they are present for a longer period of time than the flowers or fruit. Usually, the plant genus can be determined from the leaves. The species and any varieties or cultivars are often linked to color of flowers, fruit characteristics, or other minute feature and are therefore sometimes impossible to determine from leaves.
Plants are grouped into the categories deciduous and evergreen. A deciduous plant loses its leaves during the dormant season (winter) and grows a new crop of leaves in the spring. An evergreen retains foliage throughout the entire year, although it sheds older leaves from time to time.
Broadleaf and Narrowleaf. The foliage of a plant is either broad or narrow. Narrowleaf plants have leaves that are needle-like, scale-like, awl-like, or linear. These plants include the Pine, Cedar, Juniper, Fir, Spruce, Larch, Cypress, Arborvitae, and Hemlock. Narrowleaf plants are usually referred to as Conifers (cone-bearing) and are, with a few exceptions, evergreen plants. Their foliage fulfills the purpose of food manufacturing in much the same way as broadleaf plants.
Broadleaf plants have a flattened portion called the blade. They make up the majority of the plants in our environment and may be either deciduous or evergreen. Most trees and shrubs marketed in the nursery industry are broadleaf. Generally speaking, most horticulturalists refer to broadleaf plants as hardwoods, whereas conifers are referred to as softwoods.
Simple and Compound Leaves. A close examination of leaves reveals that they are either simple or compound. Simple leaves have one flattened blade, while compound leaves are composed of two or more leaflets. Sometimes a leaflet may be larger in size than many simple leaves, therefore one must learn to look for the axillary bud to determine if the leaf is simple or compound. The axillary bud is a bud in the axil, or angle, of the stem and leaf petiole. Its function is to produce a new leaf or stem. LEAFLETS DO NOT HAVE AXILLARY BUDS. Once the axillary bud is located, one need only observe what is attached to the petiole. In addition, there is an abscission layer of corky material at the point where petiole and stem meet. This allows for easy removal of the petiole from the stem, but it is not noticeable to the eye. (see Figure 1-1)
Most plants have simple leaves; however, many common native plants and cultivated landscape plants have compound leaves. Hickory, Ash, Locust, Pecan, Bald Cypress, Walnut, and Wisteria all have compound leaves, to name just a few.
Types of Compound Leaves. Compound leaves are either palmately compound, pinnately compound, or bipinnately compound. A palmately compound leaf has each leaflet attached to a common point, and the leaflets appear in a whorled pattern (Buckeye). Usually there are either 5 or 7 leaflets. Pinnately compound leaves have leaflets proportionately spaced throughout the petiole, as with the Ash or Hickory. Bipinnately compound leaves are often called twice-divided, because the petiolules contain several leaflets, and there are usually several petiolules per leaf. Honeylocust and Mimosa leaves are excellent examples of bipinnation. (see Figure 1-2)
[FIGURE 1.1 OMITTED]
[FIGURE 1.2 OMITTED]
Both compound and simple leaves vary in their pattern of arrangement along the stem. Depending upon the species, leaves may be arranged in alternate, opposite, or whorled patterns. In alternate arrangement, the leaves are alternated or staggered along the stem. This is a common pattern, and is characteristic of many plants, such as Oak trees. In an opposite arrangement, the leaves appear in opposite pairs along the stem. The petiole of each leaf in a pair is attached at the same point along the stem. This arrangement exists in many familiar plants, including Maple trees. Whorled arrangement involves the arrangement of leaves in a spiral-like pattern, with several leaf petioles attached at the same point along a stem. Many ground covers, ornamental grasses, and other landscape plants have leaves that arise from a whorled pattern at the base of the stem. Examples are Pampas Grass and the Cast Iron Plant. (see Figure 1-3)
The arrangement of leaves is extremely important in the proper identification of plants. The novice gardener or beginning student should pay close attention to this feature from the very start. In many cases, leaf arrangement is the primary consideration. For example, Tea Olives (Osmanthus) have very Holly-like leaves, complete with sharp spines or "stickers" along the margins of the leaf. All Hollies, however, have alternate arrangement, while Tea Olives have opposite arrangement. No matter how it appears, if it has opposite arrangement, it is not a Holly!
[FIGURE 1.3 OMITTED]
Emphasis must be placed upon arrangement in compound leaves. Compound leaves, like simple leaves, may be arranged differently along the stem. Beginners sometimes mistake Ash for Hickory. Both have pinnately compound leaves, but the pinnately compound leaves of the Hickory are arranged alternately along the stem, while the compound leaves of the Ash are opposite. Always use reference books and other materials that give the leaf arrangement as part of the description.
Leaf venation refers to the pattern of the primary or largest veins in a leaf. There are three main patterns of leaf venation - pinnate, palmate, and parallel. Pinnatelyveined leaves have one primary vein or midrib that extends from the petiole to the leaf tip in the center of the leaf. It has noticeable secondary veins that branch off of the midrib at regular intervals, giving a "fishbone" effect. Oaks, Birches, and Beeches are familiar examples having this type of venation. The veins of palmatelyveined leaves have several main veins that originate at the same place along the base of the leaves at the junction of the petiole. These main veins radiate in a fantype pattern and extend to the various lobes (divisions) of the leaves. Maples and Sweetgum varieties serve as the classic examples. Parallel-veined plants have many veins that run parallel to each other and to the margin of the leaf. This pattern is typical of most grasses and grass-related plants. (see Figure 1-4)
The shapes of leaves vary greatly in nature, and most references are quite confusing when describing leaves. The descriptions, along with the illustrations, should prove to be valuable reference material when identifying plants.
The overall shape of the leaf is probably the one most common feature in identifying plants. It is the feature which we notice first, and it is the most variable. The following is a brief description of each illustrated shape. (see Figure 1-5)
Needle-like. These are long, slender leaves typical of the Pines and some other conifers. The needles are arranged in bundles called fascicles and are held together at the base by a sheath. Needles appear in fascicles of 2, 3, or 5, depending upon the species.
Awl-like. This foliage is a type of needle that is small and pointed like a woodworker's awl. Many Juniper species have awl-like foliage.
Scale-like. Scale-like foliage is tiny and overlaps along the stem in a tight pattern. Scales are not sharp pointed as with awl-like foliage.
Oblong. This is a leaf type that is four times (or more) as long as it is broad, with a rounded base and tip.
Linear. A linear leaf is a flat leaf several times as long as broad, and is pointed at the tip.
Lanceolate. This is a pointed leaf that is broad at the base, giving it a lance or spearhead shape.
Oblanceolate. This type is an inverted lance with the pointed part at the base and the rounded part at the tip.
Spatulate. This shape resembles a spatula and is broad at the tip and more narrow at the base.
Ovate. An ovate leaf is two to three times as long as broad, having a pointed tip and rounded base.
Obovate. This leaf is the inverse of an ovate leaf, with the pointed part at the base. Elliptic. This is a leaf shaped like an ellipse or circular cone. It is broader in the middle, tapering to the tip and base.
Oval. This shape is similar to ovate but much broader. The width is almost equal to the length.
Cordate. This is a heart-shaped leaf with the length slightly greater than the width.
Peltate. This is a rounded leaf with the petiole attached at the center of the leaf blade.
Reniform. This leaf type is broadly heart-shaped with the width being greater than the length.
Pinnately lobed. This shape has several deeply cut lobes, with primary veins branching off the midrib to each lobe; this is characteristic of the Oaks.
Palmately lobed. Palmately lobed leaves have 3 to 7 lobes with primary veins originating at the junction of the petiole and base; an example is the Maples.
[FIGURE 1.4 OMITTED]
[FIGURE 1.5 OMITTED]
Leaf Margins, Tips, and Bases
Upon close examination of a few plants, one begins to realize the great detail of differences in leaf composition. Not only is there variation in overall shapes, but even the margins, tips (apices), and bases (petiole end) vary considerably. The following explanations and illustrations will provide a valuable reference in describing plants. Get some practical experience. Get a few leaf samples, and compare them to the drawings. You will begin to pay more attention to detail in plant leaves. (see Figure 1-6)
Leaf Margins. Leaf margins refers to the outer edge of the leaf blade. There are many plants that have similar overall shape only to vary in the margin. The following are explanations of the margins illustrated in Figure 1-6.
* Entire: the margins are smooth.
* Serrate: the margins have large, saw-like teeth that are angled forward toward the tip.
* Double Serrate: this is similar to serrate, but there are two points on each serrated lobe.
* Serrulate: the margins have small, saw-like teeth, and are much smaller than serrate.
* Crenate: crenate has large, rounded teeth on the margins.
* Dentate: this is similar to serrate, except that the saw-like teeth point outward instead of forward toward the tip.
* Incised: this margin has pointed lobes that are deeply cut toward the midrib; appearing toothed and lobed.
* Undulate: the margins are wavy.
* Lobed: this margin has deeply cut lobes that are rounded and smooth at the ends.
* Spinose: the margins contain sharp pointed spines such as for some Hollies.
Leaf Tips. The tips or apices (singular, apex) refers to the leaf end opposite the petiole. The following are illustrated in Figure 1-6.
* Acute: the tip curves broadly to a point.
* Obtuse: the tip is narrowly rounded.
* Acuminate: the tip is triangular, tapering to a long point.
* Mucronate: similar to obtuse, except that there is a point in the center of the tip.
* Cuspidate: this tip is similar to mucronate, but the point is much longer.
* Truncate: the tip is blunt and forms a 90 degree angle to the midrib.
* Emarginate: the tip is indented toward the midrib.
* Round: the tip is broadly rounded.
* Retuse: retuse has a smooth-flowing, shallow indentation at the tip.
Leaf Bases. Leaf bases, like tips, are also very diverse. The following are descriptions of the illustrations in Figure 1-6.
* Acute: the base curves broadly to a point at the petiole.
* Cuneate: the base is triangular, coming to a point at the petiole.
* Cordate: cordate has a broad heart shape.
* Oblique: one half of the blade ends at a higher point on the petiole than the other half.
* Truncate: the base is flat and forms a 90 degree angle to the midrib.
* Rounded: self explanatory.
* Hastate: each half of the blade contains a pointed lobe that projects outward.
* Sagittate: each half of the blade contains a pointed lobe that projects downward almost parallel to the petiole.
* Obtuse: this base is narrowly rounded at the petiole.
[FIGURE 1.6 OMITTED]
During the warm season, flowers become an important feature in correctly identifying plants. The arrangement pattern is generally characteristic for the plant's genus. Individual species and varieties or cultivars are more dependent upon size and color characteristics, which one learns through direct and practical experience with plants. The following are flower types commonly found in landscape plants. (see Figures 1-7 and 1-8)
Solitary. This indicates a single flower attached to the stem. Many ornamental plants fall into this category.
Spike. The peduncle (main flower stalk) contains tightly attached flowers. The spike projects upward from the foliage.
Raceme. The raceme is a drooping cluster having flowers attached to the peduncle by a pedicel or secondary flower stalk.
Panicle. This flower type has multiflowered pedicels attached along the peduncle.
Catkins. Many clusters of male (staminate) flowers are attached to a drooping peduncle.
Umbel. The umbel has flowers in which the pedicles originate at the same point along the peduncle.
Corymb. Flowers have pedicels that are attached at alternating points along the peduncle.
Head. The head is a composite of miniature flowers that appears to be one flower; Chrysanthemums are an example.
Cyme. Multiflowered pedicels attach themselves at the same point on the peduncle. The overall appearance is flattened, with the center flowers opening first.
[FIGURE 1.7 OMITTED]
[FIGURE 1.8 OMITTED]
The purpose of a typical flower is to produce a fruit that contains seeds. As a carrier for the all-important seed, a fruit is really a ripened flower ovary. When the petals of the flower have fallen, the plant channels its energy into the ovary, which increases in size and maturity before falling in late season.
Fruits are just as variable as leaf or flower types, therefore providing yet another means of plant identification. Unfortunately, fruit is present only for a relatively short period, and is usually most abundant during late summer and fall. Several fruit types are illustrated. (see Figure 1-9)
Samara. The samaras are "winged" fruits containing a seed with a transparent membrane. The membrane literally serves as a wing to propel the seed for distribution by wind; Ash, Maple, and Elm are examples.
Acorn (Nut). This is a hard fruit that contains one seed; all Oaks produce acorns. Strobile. The strobile is a small, soft, and cone-like fruit that contains many "winged" seeds; Birch is typical.
Clusters (of Small Drupes). Cluster fruits (multiple fruits) are composed of many tiny fruits developed from many flowers; Raspberry is typical.
Capsules. Capsules are hard fruits that split into two or more parts at maturity to expose the seed; the Willows have capsule fruits.
Nutlet. The nutlet is a kind of "glorified" samara but is larger; American Hornbeam is an example. Some nutlets have more than one "wing."
Cones. Cones are composed of many burs that open at maturity to disperse the "winged" seed.
Berry. Berries are fleshy fruits that contain seed randomly dispersed throughout the flesh; Blueberries are representative.
Aggregate of Samaras. This is a fruit that develops from several pistils in the same flower. Each pistil develops a samara-like fruit that contains a seed; Yellow Poplar is typical.
Aggregate of Follicles. This fruit is composed of follicles produced from many pistils. Each follicle is a fruit that splits to release many seeds; Magnolia is an example.
Drupe. Flesh surrounds a stony endocarp or stone that encloses the seed; Peach and Holly are examples.
Pome. Pome fruits are fleshy fruits that encircle a center "core" containing the seed; Apples are the best example.
Pod (Legumes). The fruit is a pod that separates into two halves and contains several seeds; Eastern Redbud and Locust trees are good examples.
Husk and Nut. The husk is a capsule fruit that splits along two or more lines to release a hard-shelled nut; typical plants are Pecan and Hickory.
[FIGURE 1.9 OMITTED]
Stems and stem parts are too varied and complex to adequately cover in this text. It is desirable that one be able to identify the plant without researching twigs and stems. However, there are keys that describe stem detail, and such keys can be used as reference materials to identify plants when the need arises.
It would be advisable for the plant enthusiast to learn the various parts of a stem, along with the functions of the parts. Figure 1-10 illustrates the parts of a typical stem. An explanation of the functions of stem parts follows. (see Figure 1-10) Terminal Bud. This is the bud at the tip of the stem that will provide for growth in length of the stem.
Lenticel. Lenticels are small, corky growths along the stem. They allow for gas exchanges between the atmosphere and plant cells. Some plants, such as Cherries, have very noticeable lenticels.
Lateral Buds. These are buds along the length of the stem that will form a new leaf or lateral branch.
Node. A node is any area along a stem where leaves or side branches are found.
Bud Scale. Bud scales are tiny scales that cover a bud before it opens and begins to grow.
Leaf Scar. This is a scar that is left when a leaf drops from the stem. Leaf scars vary among plants and are useful in identification.
Vascular Bundle Scars. These are small round holes that serve as connecting veins between the stem and leaf. They vary in number, arrangement, and pattern from plant to plant (specific).
[FIGURE 1-10 OMITTED]
Terminal Bud Scar. This is a ring-like scar that encircles the stem. It is left when the terminal bud begins to grow and increase in length. The stem adds one bud scar per year, so it is possible to determine the age of a stem by counting the bud scars on a branch or stem.
Pith. Pith is soft tissue in the center of the stem. Its color, size, texture, and other characteristics vary from plant to plant.
|Printer friendly Cite/link Email Feedback|
|Title Annotation:||SECTION 1 Data and Nomenclature|
|Author:||Bridwell, Ferrell M.|
|Publication:||Landscape Plants, Their Identification, Culture, and Use, 2nd ed.|
|Date:||Jan 1, 2003|
|Next Article:||Chapter 2 interpretation of data.|