How to Pollinate Basket Grass to Increase Your Yield

Pollination Mechanisms and Plant-Pollinator Relationships New September 2017

Candace Galen and Levi Storks, Biological Sciences, University of Missouri Ela Carpenter, Jackie Dearborn, Julia Guyton and Sean ODaniels, Fisheries and Wildlife Sciences, University of Missouri

Pollination is one of the most fascinating processes in the natural world. Pollination is how flowering plants reproduce. The process involves the transfer of pollen from the male parts to the female parts of the same or another plant. For some plants, this movement of pollen requires the action of another organism, a pollinator. Plants and their pollinators form a mutualistic relationship, a relationship in which each benefits from the other. In the plant-pollinator relationship, the pollinator benefits by feeding on food rewards provided by the flower, primarily nectar and pollen. In return, the plant benefits as the pollinator moves from flower to flower, transferring pollen as it forages for the food rewards. This movement of pollen allows the plant to reproduce and to exchange genetic information with other plants. Most flowering plants require relationships with pollinators to reproduce.

Missouri Master Pollinator Steward program

This publication is one in a series that focuses on pollinators and how you can join the efforts to protect them. In addition to these publications, the Missouri Master Pollinator Steward program offers training that includes hands-on activities aimed at building awareness of key pollinators plight and needs, and inspiring confidence in your ability to make a difference. Learn how you can become a Master Pollinator Steward.

Unfortunately, pollinator populations worldwide are in decline, which negatively affects the flowering plants that depend on them. It also means trouble for humans, as we all depend on the services of pollinators in many different ways, from the food we eat to the air we breathe. This decline in pollinator populations is due in part to human practices that have contributed to a loss of wild and flower-rich habitat. By changing some of our practices, such as how we manage flowering plants in our gardens and farms, we can help conserve these vital pollinator species.

Taxonomy is the field of study concerned with identifying, naming and classifying organisms. An understanding of taxonomy can help you select plants that are beneficial to the pollinators in your area.

Plants and animals are often called by different names in different locations. The mountain lion (Puma concolor) is also known by the common names puma, cougar and catamount. Conversely, the same common name may refer to completely different species. For example, pileated woodpeckers (Dryocopus pileatus) are called woodcocks in some areas, but the American woodcock (Scolopax minor), or timberdoodle, is not a woodpecker at all. This ambiguity in how common names are applied is why knowledge of the scientific names of plants is necessary to ensure you are selecting the plants you meant to select.

Early botanists and zoologists realized that a system of identifying organisms that eliminated such confusions would be essential for communicating descriptions of flora and fauna. In the 1700s, Carl Linnaeus, a Swedish physician and botanist, popularized a naming system in which a species is identified with two Latin names, Latin being the scientific language of the time. In this system, each organism is given a unique combination of two names, one for the genus, which is a group of related species, and one for the species. This system is referred to as binomial nomenclature, which simply means “naming with two names.” Scientific names (Genus + species) are denoted in italics, by convention, so they are easily recognizable in publications, as illustrated in the paragraph above. Subsequent uses of the same genus name within a publication are often abbreviated to the first letter, for example, D. pileatus.

High school biology students often learn some variation of the mnemonic “King Phillip Came Over From Germany Sunday” as a means of remembering the order of the taxonomic levels.

• Kingdom
  • Phylum
    • Class
      • Order
        • Family
          • Genus
            • Species

When spp. follows a genus name, it simply indicates that the name refers to multiple species in that genus.

The Linnaean binomial system gives us a way to identify and communicate species names across geographic regions and languages, but the field of taxonomy deals with classifying organisms from the broadest of shared characteristics down to those found only in each unique species. Traditionally, there are seven main taxonomic levels, or hierarchies: kingdom, phylum, class, order, family, genus and species. To examine each level more in depth, consider the taxonomy of a very well-known insect pollinator, the common, or European, honey bee (Apis mellifera) (Table 1).

Table 1 Taxonomy of the European honey bee.

Taxonomic level	Scientific name	Common name
Kingdom	Animalia	Animals
Phylum	Arthropoda	Insects, spiders, crabs, lobsters
Class	Insecta	Insects
Order	Hymenoptera	Ants, bees, wasps
Family	Apidae	Social bees (hive or colony)
Genus	Apis	Honey bees (four species)
Species	mellifera	European honey bee

The variety of organisms narrows at each level of the taxonomy, as indicated by the associated common names. Organisms are grouped at each level based on shared features. As the number of features they have in common increases, fewer organisms exist that share them all. This description of how closely related organisms are to one another is the central theme of taxonomy. Shared features that are useful for taxonomy are often physical traits, such as number of wings or legs; however, in some cases, behaviors can also be useful, as in the family Apidae, which consists hive-nesting or social bees.

Cultivated plant species are additionally classified as varieties. Different varieties have been modified through crop-breeding programs to either enhance or eliminate traits present in the native, or wild-type, organism. The taxonomy of the wild cabbage (Brassica oleracea) serves as an example (Table 2). It and several other of our common vegetables are varieties of the same species.

Naming systems for plants and animals are similar, but have a few differences, especially at the family level. Animal family names end with -idae (for example, Apidae, Nymphalidae), whereas plant family names end with -aceae (for example, Fabaceae, Rosaceae). This chapter mainly discusses plant-pollinator relationships at the family level, so a general understanding of these naming conventions will be helpful.

Table 2 Taxonomy of the wild cabbage.

Taxonomic level	Scientific name	Common name
Kingdom	Plantae	Plants
Phylum	Magnoliophyta	Flowering plants (angiosperms)
Class	Magnoliopsida	Dicotyledons (dicots)
Order	Capparales
Family	Brassicaceae	Mustard family
Genus	Brassica	Mustards
Species	oleracea	Cabbage, broccoli, Brussel sprouts, cauliflower, collard greens, kale, kohlrabi

To gain an understanding of how knowledge of taxonomy can be useful, examine the following plant-pollinator relationships.

Traits shared at the family level are often the most useful in recognizing and describing related organisms. For plants, these traits are not always visible. For example, plants of the Fabaceae family are excellent soil nitrogen fixers, making them ideal cover crops. Honey bees can often be found — and stepped on — in patches of white clover (Trifolium repens) (Table 3). However, white clover is not native to North America, so producers interested in using cover crops in their fields may want to investigate native Fabaceae, such as purple prairie clover (Dalea purpurea), which may also better support native pollinators such as bumble bees (Bombus spp.). Bumble bees share the Apidae family with honey bees (A. mellifera) and carpenter bees (Ceratina spp. and Xyolocopa virginica), among others.

Taxonomy also reveals that species that may outwardly appear to be unrelated, actually have more in common than is first apparent. People are often surprised to learn that watermelons (Citrullus lanatus) and cucumbers (Cucumis sativus) are in the same family, Cucurbitaceae, which also includes cantaloupe, honeydew, pumpkins and squash (Table 4).

All members of this family have imperfect flowers, meaning flowers that have either male or female reproductive organs, and they make pollen grains that are too heavy and sticky to be moved by wind. Thus, pollinators are required for these plants to produce fruits. Honey bees can provide this service, but our native bumble bees may be better suited for this task early in the season because they remain active during cooler, wetter weather unlike honey bees.

Apples (Malus domestica) also require pollinators to produce fruits. Although apple blossoms have perfect flowers, that is, flowers that contain both male and female structures, most varieties are self-sterile, meaning a tree cannot pollinate its own flowers. Thus, for trees to produce apples, pollen must be transferred from one tree to another, a process called cross-pollination. As is the case with cabbage (B. oleracea), the many varieties of apple are all Malus domestica (Table 5).

Other fruit trees within the Rosaceae family include peach (Prunus persica) and cherry (P. avium), both of which also come in many varieties.

Mason bees (Osmia spp.) are solitary nesting, native pollinators that specialize in pollinating Rosaceae fruit trees. Because of this specialization, they are often called orchard bees. There are 140 species of mason bee in North America. The blue orchard bee (Osmia lignaria) is one of the few native bees managed for agriculture due to its efficiency as a pollinator. Mason bees belong to the family Megachilidae, as do leafcutter bees (Megachile spp.), another common orchard pollinator that shares the solitary nesting trait (Table 6).

Table 3 Taxonomy of the white clover.

Taxonomic level	Scientific name	Common name
Kingdom	Plantae	Plants
Phylum	Magnoliophyta	Flowering plants (angiosperms)
Class	Magnoliopsida	Dicotyledons (dicots)
Order	Fabales
Family	Fabaceae	Pea family (legumes)
Genus	Trifolium	Clovers
Species	repens	White clover

Table 4 Taxonomy of the watermelon and the cucumber.

Taxonomic level	Watermelon	Cucumber
Kingdom	Plantae	Plantae
Phylum	Magnoliophyta	Magnoliophyta
Class	Magnoliopsida	Magnoliopsida
Order	Cucurbitales	Cucurbitales
Family	Cucurbitaceae	Cucurbitaceae
Genus	Citrullus	Cucumis
Species	lanatus	sativus

Table 5 Taxonomy of the apple.

Taxonomic level	Scientific name	Common name
Kingdom	Plantae	Plants
Phylum	Magnoliophyta	Flowering plants (angiosperms)
Class	Magnoliopsida	Dicotyledons (dicots)
Order	Rosales
Family	Rosaceae	Rose family
Genus	Malus	Apple and crab apple
Species	domestica	Apple (“orchard”, domestic)

Table 6 Taxonomy of the blue orchard bee and the leafcutter bee.

Taxonomic level	Blue orchard bee	Leafcutter bee
Kingdom	Animalia	Animalia
Phylum	Arthropoda	Arthropoda
Class	Insecta	Insecta
Order	Hymenoptera	Hymenoptera
Family	Megachilidae	Megachilidae
Genus	Osmia	Megachile
Species	lignaria	242 species (in North America)

Bees are by no means the only insect pollinators worthy of mention. Flies (order Diptera), beetles (order Coleoptera), butterflies and moths (order Lepidoptera), and wasps (order Hymenoptera) are important pollinators as well, and some have developed specialized relationships with their preferred host plants. Some of these specialized plant-pollinator relationships are described in later sections.

An understanding of plant and pollinator taxonomy can be valuable for mastering knowledge of pollination and improving your propertys capacity to support pollinators and thus your harvest.

Taxonomy can help you recognize that plants that may outwardly appear unrelated, such as watermelons and cucumbers, are in fact closely related and thus may share a need for the same animal pollinators.

Taxonomy can also inform sustainable agriculture practices. For example, plants in the Fabaceae family can help replace soil nitrogen levels between crop rotations while benefiting native pollinators, such as bumble bees.

With a basic knowledge of taxonomy, a quick glance at the taxonomic hierarchy of an organism provides information on its pollination or host plant requirements, and thus on benefits of its presence on your land.

To practice applying your taxonomical knowledge, fill in the chart below with the complete taxonomy of the golden northern bumble bee (B. fervidas) and the red clover (T. pratense) using only information presented in this section.

Taxonomic level	Red clover	Golden northern bumble bee

Flowers are the reproductive structures of angiosperms, or flowering plants. Angiosperms comprise most of our food and fiber crops. Nearly all flowering plants require pollination to produce seeds and fruits; these include most of our edible fruit and vegetable crops.

In pollination, pollen is transported from the male parts of a flower to the female parts of the same flower or a different flower of the same species. Pollen is a fine, powdery substance made up of microscopic particles or grains. Pollen, especially the small light grains adapted to wind pollination, is usually the cause of spring allergies.

Plants have evolved many different shapes, sizes and colors of flowers to attract animal pollinators. These animal-pollinated flowers are typically brightly colored and fragrant, whereas wind-pollinated flowers are typically smaller, dull in color and unscented.

From a pollinators perspective, a flower provides food, typically in the form of nectar and pollen. Nectar is produced by glands called nectaries, which can be located on any part of the plant but are commonly found in the flower. These floral nectaries are typically located near the base of the flower, requiring pollinators to contact the flowers reproductive structures while sipping the nectar and, thus, facilitating pollination.

Pumpkins (Cucurbita pepo) belong to the Cucurbitaceae family, as do watermelon and cucumber. Therefore, pollinators will be required for plants to produce pumpkins. If your pumpkin plants are not producing as expected, try raising honey bees on your farm.

Planting cover crops, such as clovers, between rows of cash crops can not only improve soil nitrogen levels but also increase cash crop yields as a result of the presence of pollinators attracted by the cover crops.

Research the family, genus or species names on plant tags before buying plants for your garden and flower beds. Beware, some tags are more informative than others.

A knowledge of basic flower anatomy can aid in understanding how plants reproduce (Figure 1). Flowers are generally comprised of four whorls of parts: the calyx, corolla, androecium and gynoecium. Each whorl contains a set of organs: sepals, petals, stamens and carpels, respectively.

Figure 1 Basic flower anatomy: a perfect flower containing male and female organs.

Calyx Sepals of the calyx look similar to leaves and surround the unopened bud. The sepals protect the flower before it opens and may remain attached to the base of the flower afterward. Sepals are typically green and smaller than the petals, but they can also be large and brightly colored, resembling petals. When sepals and petals are identical in appearance, they are called tepals.

Corolla The corolla typically encircles the reproductive parts of the flower and may be continuous, lobed, or divided into separate petals. Petals also help protect the reproductive organs of the flower, but primarily serve to attract pollinators. To succeed in attracting pollinators, petals are often brightly colored and fragrant.

Androecium The next whorl in, the androecium, is comprised of stamens, the male reproductive organs of the flowering plant. Stamens are made up of two parts: a thin stringlike stalk called a filament and the pollen-producing organ at its tip, called the anther.

Gynoecium The innermost whorl of the flower, the gynoecium, contains the female reproductive parts of the flowering plant. The carpels that make up the gynoecium may be separate or fused to form a compound pistil. The pistil is made up of three parts: the ovary, the style and the stigma. The ovary holds the unfertilized seed, or ovules, and typically develops into a fruit once pollination takes place. The stigma is the uppermost section of the pistil at the tip of the style, and receives the pollen. To catch the pollen, the stigma is commonly sticky, or covered with small hairs or grooves.

Other structural parts At the base of a flower are two more structural parts, the receptacle and pedicle. The receptacle is simply the base of the flower, and it is supported by the pedicel, or flower stalk.

Pollination is the first step in sexual reproduction of seed plants. Most angiosperms have perfect flowers, but some produce imperfect flowers. A perfect flower contains male and female reproductive organs (Figure 1). An imperfect flower has only male or only female reproductive organs (Figure 2).

To describe a plant as a whole, botanists use the terms monoecious and dioecious (Figure 2). A monoecious plant has male and female reproductive organs on the same plant. Monoecious plants can have either perfect or imperfect flowers. Examples of monoecious species in Missouri are wild plum (Prunus americana), with perfect flowers, and pumpkins, with imperfect flowers. Dioecious plants have male and female flowers on separate plants. The native persimmon (Diospyros virginiana) is a dioecious plant commonly found in Missouri. Because dioecious plants have male and female flowers on separate plants, two plants of different sexes need to be near each other for fruit production to occur. Keep this need in mind when selecting plants for your garden, and make sure you have ample space for plants of both sexes.

Figure 2 Monoecious plants have either (a) perfect flowers or (b) imperfect flowers. Dioecious plants have (c) male and female flowers on separate plants.

Figure 3 Flower shapes.

• Complete Flowers with sepals, petals, stamens and pistil
• Incomplete Flower lacking one or more whorls of parts
• Pistillate Flowers with only female parts
• Staminate Flowers with only male parts

Flowers come in various shapes and sizes (Figure 3). These differences are often related to their mode of pollination.

Flowers of wind-pollinated plants typically have very small or no petals, making it easier for airborne pollen to come in contact with the stigma.

Flowers of animal-pollinated plants usually have larger showy petals of different shapes and sizes to attract pollinators. Flower shape can provide a clue as to what animals might serve as pollinators for a plant. For example, lipped, or labiate, flowers usually provide a platform on which bumble bees can land before entering the flower, whereas long tubular flowers are frequented by hummingbirds, who hover while probing the deep flowers with their long beaks. Some common flower shapes are described below.

• Campanulate Bell-shaped flower
• Cruciform Cross-shaped flower with four petals
• Cupuliform Cup-shaped flower without spreading petal tips
• Funnelform Funnel-shaped flower that broadens from the base to the tip
• Labiate Flower with liplike petals
• Reflexed Flower with petals that are curved backwards
• Salverform Tubular flower that spreads at the tip
• Spurred Flower with petals formed into spurs that usually contain nectar
• Stellate Star-shaped flower, usually with five petals
• Tubular Cylindrical, tube-shaped flower

Flowers can be arranged singly or in clusters attached to a central stem. When flowers are arranged in clusters, or groups, on a central stem, they form an inflorescence. The main stem of an inflorescence is called the peduncle. Inflorescences come in many shapes and arrangements (Figure 4).

The flower head of a sunflower (genus Helianthus, family Asteraceae) is actually an inflorescence, not a single flower. Sunflowers are made up of hundreds of tiny flowers called florets. This multitude of florets is very effective at attracting pollinators, producing hundreds of seeds that provide food for various animals.

Figure 4 Kinds of inflorescences.

Flowers come in many different shapes, with different organs, and in different arrangements. This diversity of flower designs has evolved to accomplish the task of pollination. The plants that require animal pollinators have in turn evolved to attract specific pollinators that can provide this service. Knowledge of how flowering plants reproduce is valuable for any gardener to ensure that ovules can be fertilized, seeds set, and delicious fruit produced for harvest. A basic knowledge of flower anatomy can also be helpful for commercial farmers in choosing which crop plants to grow and how many might be needed for adequate pollination. Plus, as illustrated by the tubular flowers of hummingbird host plants, knowing the shape of a flower can give you a clue about its special pollinators.

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