Aromatic Blooms: Choosing Fragrant Flower Seeds

Flowers produce aromas to attract pollinators and communicate with other plants. The scent of a flower is composed of volatile organic compounds (VOCs) or aroma compounds emitted by floral tissue. Some flowers, like orchids, have specialised scent glands called osmophores that ooze liquid scent, while others produce scents across their petals. Flowers can be generalists, attracting a wide range of insects and birds, or specialists, emitting scents that appeal to only one type of insect. Many factors influence plant communication and signalling, including temperature and plant density. The scent of flowers is also influenced by environmental conditions, such as temperature, CO2 concentration, hydric stress, and soil nutrient status.

Flowers with strong scents include orchids, petunias, and snapdragons

Orchids are known for their specialized scent glands, called osmophores, which ooze a liquid scent that quickly evaporates when exposed to air. There are over 20,000 orchid species, ranging from the white vanilla plant to more colorful varieties. The floral scent of orchids can consist of up to 100 different chemicals, making them one of the most fragrant flowers.

Petunias, on the other hand, are often studied as models for odor-producing flowers. They release their scent in the evening, making them ideal for people to enjoy after returning home from work. The process by which petunias create amino acids and volatile scents is still being explored through biochemical studies.

Snapdragons are unique in that they have evolved a close relationship with bumblebees. These flowers release four times more scent during the day when the bees are most active. The floral scents are strategically released only on the lobes of the petals, ensuring that bees come into contact with the scent and carry it back to the hive, attracting more bees.

While these three types of flowers are known for their strong scents, it's important to note that modern plant breeding has caused many popular flowers to lose the scent of their ancestors. However, with ongoing research, scientists may be able to genetically engineer plants to produce stronger fragrances.

Flowers use scent to attract pollinators and communicate with other plants

Flowers have evolved to use scent to attract pollinators and communicate with other plants. Floral scent, or flower scent, is composed of volatile organic compounds (VOCs) or aroma compounds emitted by floral tissue. The primary functions of floral scent are to deter herbivores and attract pollinators.

Plants use floral scents to attract pollinators or to repel harmful insects. Floral scents begin as oils that are produced by the petals in most plants. Because these oils evaporate easily in warm weather, scientists call them volatile compounds. The aroma of a flower may contain as few as seven to ten different oils, as in snapdragons or petunias, or as many as 100 different chemicals, as is the case with orchids.

Flowers use many traits to influence animal pollinator visitation, including colour, shape, and scent. By making sure that the “right” pollinators visit in the right way, plants can ensure that their pollen is successfully transferred.

Plants have an array of volatile compounds they can release to signal other plants. By unleashing these cues, plants learn more about their environment and respond accordingly. For example, in sexually deceptive orchids, floral scents emitted after pollination reduce the flower's attractiveness to pollinators, acting as a signal to visit unpollinated flowers.

Environmental conditions can also affect plant communication and signaling. For instance, environmentally high temperatures increase the rate of releasing floral compounds, which can increase the amount of signal released and thus its ability to reach more plants.

Flowers can be identical in their colour or shape, but no two floral scents are exactly the same because of the diversity of volatile compounds, relative abundances, and interactions. A pollinator detects a flower's scent and follows the concentration gradient of the chemical producing the scent to the flower.

Plants' scent levels tend to be highest when the flowers are ready for pollination and when potential pollinators are active. Bees or butterflies pollinate plants whose scent is highest during the day, while moths and bats pollinate plants with the strongest fragrance at night.

The scent of flowers is made up of volatile organic compounds (VOCs) or aroma compounds

VOCs are emitted by both petals and pollen of garden roses. The most common VOCs are 2-phenylethanol, methyl eugenol, and hexanal. The VOCs emitted by petals were more than five times higher than that produced by pollen.

Flowers can be bred to maximise colour and shape at the expense of scent

Flowers are bred for their aesthetic appeal, but this can come at the cost of their scent. Modern plant breeding has led to many popular flowers losing their fragrance. For example, roses, which were once known for their evocative scent, have been bred to prioritise longevity, resulting in a loss of fragrance. This is common among flowers sold in supermarkets and flower shops, where consumers expect fresh, long-lasting flowers. The international flower market ships flowers globally, and roses, for instance, are often bred to withstand transportation and be affordable, which can mean that scent is compromised.

The scent of flowers is integral to their survival, as it attracts pollinators. Floral scents are composed of volatile organic compounds (VOCs) or aroma compounds, emitted by the floral tissue. The scent of a flower can contain as few as seven to ten different oils, like snapdragons, or as many as 100 different chemicals, as seen in orchids. The scent of a flower, along with its colour and shape, is one of the most important communication channels for plant-pollinator interactions.

Flowers use their scent to attract specific pollinators, and the pollinators, in turn, are lured to a particular flower because of its scent. For example, snapdragons have evolved a close relationship with bumblebees. The snapdragon releases four times more scent during the day when the bees are active. The scent is released only on the lobes of the petals, and when the bee brushes against the upper lobe, it carries the scent back to the hive, attracting more bees.

The colour of flowers is also important in attracting pollinators. Flowers that depend on insects, birds, or bees for pollination tend to have bright, vivid colours that help them stand out. Flowers that rely on the wind for pollination, on the other hand, are usually duller in hue. Scientists have found that certain pollinators show a preference for individual flower species based on colour and will even choose specific shades.

While breeding flowers for colour and shape can reduce their scent, it is important to note that some flowers are naturally more fragrant than others. Examples of highly fragrant flowers include lilies, lilacs, hyacinths, narcissus, daffodils, and gardenias. These flowers offer a range of scents, from spicy to sweet, and their fragrance can fill an entire garden or room.

Some flowers with strong scents include roses, lilies, and lavender

Flowers produce aromas through volatile organic compounds (VOCs) or aroma compounds, which are emitted by floral tissue, such as flower petals. These compounds are released to attract pollinators and communicate with other plants. Some flowers, like orchids, have specialised scent glands called osmophores that ooze liquid scents.

Roses, lilies, and lavender are flowers with strong scents. Roses, for example, have a range of fragrances, from citrusy to floral, musky, or fruity. Lilies, such as the 'Star Gazer' Oriental lily, can perfume an entire garden with their powerful scent. Lavender, on the other hand, produces a more delicate aroma that permeates the countryside of southern France in mid-summer.

In addition to these well-known fragrant flowers, there are several other plant species that produce notable scents. Dianthus, an old-fashioned cottage garden favourite, has a spicy, clove-like fragrance. Nicotiana, a relative of tobacco, fills gardens with a strong, sweet fragrance, especially at night. Gardenia, a shrub that thrives in warmer climates, is known for its beloved scent and makes a fragrant houseplant as well.

Unfortunately, modern plant breeding has resulted in a loss of scent in many popular flowers, as plants have been cultivated to prioritise characteristics like colour and shape, as well as long-lasting blooms after cutting. However, there is ongoing research, such as that conducted by Natalia Dudareva at Purdue University, aimed at understanding the biology of floral scents and potentially creating sweeter-smelling flowers.

Frequently asked questions