People often prioritize aesthetics when choosing plants for their gardens. They may pick flowers based on colors that create visually appealing combinations and varieties that have bigger and brighter displays or more fragrant and pleasant-smelling flowers. Some may also choose species that bloom at different times in order to maintain a colorful display throughout the growing season.

Many gardeners also strive for ecological harmony, seeking to maintain pollinator-friendly gardens that support bees, butterflies, hummingbirds and other pollinators. But there are some notable ways in which the preferences of humans and pollinators have the potential to diverge, with negative consequences for pollinators.

As a cognitive ecologist who studies animal decision-making, I find that understanding how pollinators learn about and choose between flowers can add a helpful perspective to garden aesthetics.

Pollinator preferences and rewards

Over millions of years, plants have evolved suites of floral traits to attract specific types of pollinators.

Pollinators can be attracted to flowers based on color, pattern, scent and texture. For instance, hummingbirds typically visit bright red and orange flowers with narrow openings and a tubular shape. The striking red cardinal flower is one that is primarily pollinated by hummingbirds, for example.

Bees are often attracted to blue, yellow and white flowers that can be either narrow and tubular or open. Lavender, sage and sunflower plants all bear flowers that attract bee pollinators.

Flowers offer rewards to visiting pollinators. Nectar is a sugar-rich solution that flowers produce to attract pollinators, which use it to meet their energy needs.

Flowers have an ulterior motive for providing this energy source. While drinking the nectar, pollen can get stuck on the pollinator and transferred to the next flower it visits. This process is essential for the plant’s reproductive success. Pollen contains the plants’ male gametes, which, when deposited onto another flower in the right place, can fertilize the female gametes and produce seeds that grow into new plants. Pollen is also nutrient-rich, containing proteins, lipids and amino acids. Many species, such as bees, collect pollen to feed their developing young.

A battle for resources

Pollinators visit flowers in search of floral rewards. But modifying the features of flowers for aesthetics can be a hindrance to pollinators trying to get these rewards. For example, popular garden plants such as roses and peonies are often bred to have more petals and larger flower heads, making them more visually striking and appealing to humans. But these extra petals may block a pollinator’s access to the center of the flower, where floral rewards are located.

Further, plants have limited resources. Spending them on building aesthetically pleasing but energetically expensive features can mean there’s less left to invest in signals and rewards essential for attracting pollinators. In extreme cases, breeding for aesthetics has led to plants with what scientists and gardeners call “double flowers.” In these varieties, extra petals replace reproductive parts entirely. These plants are often altogether unrewarding for pollinators, since the flowers no longer produce nectar or pollen. Double flowers occur from mutations that convert the pollen-producing stamens and other reproductive organs into petals. They can occur naturally but are rare in wild populations.

Since these double flowers cannot spread pollen or produce seeds effectively, they are unable to reproduce in the wild and pass these mutations on. To cultivate them as garden varieties, people propagate these plants through cuttings – small sections cut from the stem that can be rooted to grow clones of the parent plant. Many common garden plants have popular double-flowered varieties, including roses, peonies, camellias, marigolds, tulips, dahlias and chrysanthemums.

Roses, for example, have become synonymous with having many densely-packed petals. But these popular garden varieties are usually double-flowered or have many extra petals blocking access to the center of the rose and provide no rewards to pollinators.

Consider making your gardens friendlier to pollinators by avoiding these double-flowered plants, and ask your local garden center for recommended varieties if you need help.

Sometimes gardeners intentionally prevent plants from flowering, which limits or eliminates their value to pollinators.

For example, herbs such as thyme, oregano, mint and basil are generally most flavorful and tender before the plant begins to flower. Once it flowers, the plant diverts energy to reproductive structures, and leaves become tougher and lose flavor. As a result, gardeners often pinch off flower buds and harvest leaves frequently to promote continued growth and delay flowering. Letting some of your herbs flower occasionally can help pollinators without affecting your kitchen supplies too much.

Finding the right flowers

Flowers with unusual colors and stronger fragrances can be difficult for pollinators to detect and recognize.

People might favor bright and unusual flower colors in their gardens over naturally occurring shades. But this preference might not align with what the pollinators have evolved to favor in nature. For example, planting human-preferred colors, such as white or pink morphs of hummingbird-pollinated flowers that are typically red, can reduce a flower’s visibility and attractiveness. Even when cultivated varieties have a similar enough color to natural ones to attract pollinators, they may lack other important visual components, such as ultraviolet floral patterns that can guide pollinators to nectar sources.

Breeding plant varieties to accentuate particular aesthetic traits may have unintended consequences for other traits. Changes in flower color through selective breeding can also affect leaf color, as genes involved in pigment production can affect multiple plant tissues. Besides changing the overall appearance of the plant, changing leaf color may alter background contrast between flowers and the leaves, which can make flowers less conspicuous to pollinators.

Many pollinators use a combination of color and scent to detect and discriminate between flowers. But breeding for traits such as color and brightness can alter floral scents due to unintended genetic changes or energetic trade-offs.

Scent helps pollinators locate flowers from farther distances, so unfamiliar or reduced fragrance may make flowers harder to find in the first place. Disruption in either color or scent can make flowers less noticeable to pollinators expecting a familiar pairing and can hinder a pollinator’s ability to learn which flowers are suitable for them in the first place.

A balanced approach for healthy gardens

When flowers are harder to find, pollinators are less likely to visit them. When they offer poor or no rewards, pollinators quickly abandon them for better options. This disruption in plant-pollinator interactions has implications not only for pollinator health but also for garden vitality. Many plants rely on animal pollinators to reproduce and make mature seeds. These are either collected by gardeners or allowed to drop to the ground and sprout on their own to grow new flowering plants the following year.

When selecting plants for a garden, gardeners who want to support pollinators might consider choosing native varieties that have evolved alongside local pollinators.

In most areas of the country, there are native plants with colorful and interesting flowers that bloom at different times, from early spring to late fall. These plants tend to produce reliable floral signals and offer the nectar and pollen needed to support pollinator nutrition and development.

Sterile varieties and double flowers offer little or no rewards for pollinators, and gardens with them may not attract as many pollinators. Letting herbs flower after some harvesting is another simple way to support beneficial insects.

With choices informed by not just your aesthetic preferences but also those of pollinators, you can create colorful gardens that support wildlife and stay in bloom across various seasons.

Claire Therese Hemingway, Assistant Professor of Ecology & Evolutionary Biology, University of Tennessee

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Just like people confronted with a sea of options at the grocery store, bees foraging in meadows encounter many different flowers at once. They must decide which ones to visit for food, but it isn’t always a straightforward choice.

Flowers offer two types of food: nectar and pollen, which can vary in important ways. Nectar, for instance, can fluctuate in concentration, volume, refill rate and accessibility. It also contains secondary metabolites, such as caffeine and nicotine, which can be either disagreeable or appealing, depending on how much is present. Similarly, pollen contains proteins and lipids, which affect nutritional quality.

When confronted with these choices, you’d think bees would always pick the flowers with the most accessible, highest-quality nectar and pollen. But they don’t. Instead, just like human grocery shoppers, their decisions about which flowers to visit depend on their recent experience with similar flowers and what other flowers are available.

I find these behaviors fascinating. My research looks at how animals make daily choices – especially when looking for food. It turns out that bees and other pollinators make the same kinds of irrational “shopping” decisions humans make.

Predictably irrational

Humans are sometimes illogical. For instance, someone who wins $5 on a scratch ticket immediately after winning $1 on one will be thrilled – whereas that same person winning $5 on a ticket might be disappointed if they’re coming off a $10 win. Even though the outcome is the same, perception changes depending on what came before.

Perceptions are also at play when people assess product labels. For instance, a person may expect an expensive bottle of wine with a fancy French label to be better than a cheap, generic-looking one. But if there’s a mismatch between how good something is and how good someone expects it to be, they may feel disproportionately disappointed or delighted.

Humans are also very sensitive to the context of their choice. For example, people are more likely to pay a higher price for a television when a smaller, more expensive one is also available.

These irrational behaviors are so predictable, companies have devised clever ways to exploit these tendencies when pricing and packaging goods, creating commercials, stocking shelves, and designing websites and apps. Even outside of a consumer setting, these behaviors are so common that they influence how politicians design public policy and attempt to influence voting behavior.

Like minds

Research shows bumblebees and humans share many of these behaviors. A 2005 study found bees evaluate the quality of nectar relative to their most recent feeding experience: Bees trained to visit a feeder with medium-quality nectar accepted it readily, whereas bees trained to visit a feeder with high-quality nectar often rejected medium-quality nectar.

My team and I wanted to explore whether floral traits such as scents, colors and patterns might serve as product labels for bees. In the lab, we trained groups of bees to associate certain artificial flower colors with high-quality “nectar” – actually a sugar solution we could manipulate.

For example, we trained one group to associate blue flowers with high-quality nectar. We then offered that group medium-quality nectar in either blue or yellow flowers.

We found the bees were more willing to accept the medium-quality nectar from yellow flowers than they were from blue. Their expectations mattered.

In another recent experiment, we gave bumblebees a choice between two equally attractive flowers – one high in sugar concentration but slower to refill and one quick to refill but containing less sugar. We measured their preference between the two, which was similar.

We then expanded the choice by including a third flower that was even lower in sugar concentration or even slower to refill. We found that the presence of the new low-reward flower made the intermediate one appear relatively better.

These results are intriguing and suggest, for both bees and other animals, available choices may guide foraging decisions.

Potential uses

Understanding these behaviors in bumblebees and other pollinators may have important consequences for people. Honeybees and bumblebees are used commercially to support billions of dollars of crop production annually.

If bees visit certain flowers more in the presence of other flowers, farmers could use this tendency strategically. Just as stores stock shelves to present unattractive options alongside attractive ones, farmers could plant certain flower species in or near crop plants to increase visitation to the target crops.

Claire Therese Hemingway, Assistant Professor of Ecology & Evolutionary Biology, University of Tennessee

This article is republished from The Conversation under a Creative Commons license. Read the original article.