Why Do Annual Flowers Die? The Science Explained

Broadly speaking, the flowers that you plant in your garden can be separated into three categories: perennial flowers, biennial flowers, and annual flowers. Perennial flowers return year after year and similarly, biennial flowers bloom through their two-year life cycle, while annual flowers only bloom once before dying afterward. But why is it that annual flowers don’t return like other types of flowers?

The reason that annual flowers die at the end of their flowering season is due to a difference in genetics between annual flowers and other flowers. Annual flowers use all their non-specialized cells to create flowers, and end up dying afterward.

In this article, I’ll give you more information on the different types of flowers and the process that causes annual flowers to die. You’ll get a better understanding of how your flowers work, which will help you become a more knowledgeable gardener.

What Are Perennial Flowers?

Perennial flowers are flowers that regrow and bloom again every season. They store energy in the flower bulb underneath the ground through their dormant period in the colder months, using that energy to return once the weather warms up again.

It’s important to note that a perennial flower needs the right conditions to grow back again in consecutive seasons. Failure to receive adequate water or sunlight can lead to the flower not gathering the energy required to regrow in the coming year. If a flower bulb is planted in poorly-draining soil, it may also rot due to the excessive moisture, which would also cause the flower to fail to regrow.

You can help your perennials regrow by giving them the nutrients they need. Assisting them conserve their energy by trimming away flowers after they wilt will also help them have more energy for the following season. You can also avoid potential problems by managing pests in your garden that may target flower bulbs.

What Are Biennial Flowers?

Biennial flowers follow a two-year cycle, growing roots, stems, and leaves in their first season before going dormant through the winter. They return the following spring, producing flowers and seeds before reaching the end of their life cycle.

This lesser-known category of plants takes some time to provide you with the flowers you’re looking for, making them more suitable for experienced gardeners. However, if you know how to cultivate this plant correctly, you can eventually achieve a yearly bloom as the current year’s flowers continuously replace the ones dying off that year.

A number of leafy-green vegetables, such as spinach, lettuce, or fennel, are biennial plants. However, people who grow these plants tend to avoid letting them reach the flowering stage of their life cycle known as ‘bolting’ as flowering tends to render the plant inedible.

What Are Annual Flowers?

Annual flowers complete their life cycle within just one year. New plants must be grown from seeds or cuttings to get these flowers to return to your garden the following season.

The entirety of an annual plant, root and stem, dies at the conclusion of its blooming period. This means caring for the dormant seeds that the flower produces at the end of its life cycle is crucial. Provide these seeds with the care they need in order to continue having that type of flower thrive in your garden.

The reason why annual flowers developed this life cycle is that it gave them an advantage in competing with other flowers. The germination from seed to flower that annuals experience is a much quicker process than that of perennial flowers regrowing from their bulbs. This allows annual plants to grow and flower early in the season, reducing their need to compete with other plants for resources.

What Causes Annual Flowers To Die?

The reason annual flowers die at the end of their blooming period is due to the way these flowers use non-specialized cells. Annual flowers use all of their non-specialized cells to create flowers, thereby ending their life cycle.

A non-specialized cell is any cell that hasn’t been committed to any specific function. Humans and other animals use these types of cells as well. For example, stem cells are utilized in the human body, turning into any number of organs or other body parts as we grow older and new cells are needed for certain functions.

The way annual flowers use their non-specialized cells differs from the way perennial or biennial flowers do. Perennials and biennial plants conserve non-specialized cells so that they can form new structures in the coming seasons. Annual flowers, on the other hand, use all their non-specialized cells in the formation of flowers and seeds. Once the plant drops those seeds, the plant then dies.

Interestingly, genetic modification experiments have shown that by altering the genome of annual plants, scientists can induce the plants to change their behavior. The annual plants lose their ability to form their characteristic blooms in this case, and begin following a perennial growing pattern. 

If you want a better understanding of how non-specialized cells in plants work, you can check out this research for a more detailed explanation.

Popular Types of Annual Flowers

Wondering if the flowers you’re thinking of adding to your garden are annuals? Here are some of the more common types of this class of flowers and some introductory information on each.


Named for the beautiful golden colors that they produce, marigolds are an annual flower that requires minimal effort to grow successfully. This makes them a great flower for any beginner gardeners looking to gain more experience. They bloom in approximately eight weeks, giving you a quick sense of satisfaction when you see their beautiful bloom popping.


Another annual flower that is exceptionally easy to care for, geraniums produce a bright flower that is certain to impress anybody who sees it growing in your garden. They do well as potted flowers as well, adding a splash of color to any interior design project you may have in mind.


With lovely, full blooms and a variety of colors available in all their different types, impatiens are another highly popular annual flower among gardeners. They are a relatively low-maintenance plant, but are not that drought resistant, requiring regular watering through long dry periods where they aren’t receiving any rainfall.


Better known as summer snapdragons, angelonia have a distinctive shape that gives them a unique character, helping them add an eye-catching look to any garden. These flowers thrive in the heat, making them ideal for gardeners who live in hot and humid climates. Their ability to withstand the heat will have this flower providing color to your garden well into the summer.


Though the flowers that begonias produce are rather small, their vibrant colors have made them a favorite of gardeners all over the world. These plants thrive best in partially-shaded areas, making them perfect as houseplants or to add to a part of your garden that doesn’t receive as much direct sunlight as others.


A plant that offers you plenty of variety, petunias come in every size from dime-sized to trailing plants that reach up to four feet (1.21m), and in a variety of different colors. Although these plants are technically perennials, they are usually grown as annuals in most climates since they don’t tolerate frost very well.


Verbena plants bloom all season long, giving your garden a vibrant dash of color that lasts longer than many other annual flowers do. They tolerate hot and dry conditions quite well, making them a hassle-free flower to grow, and also thrive in pots, flower boxes, or hanging baskets.

Final Thoughts

The difference between annual flowers and other plants is in the way they’ve adapted to thrive in nature. Annual flowers go through their flowering and seeding cycle in just one season, allowing them to flower early in the season when they don’t have to compete with other flowers. The trade-off is that they use all their non-specialized cells in doing so, typically dying afterwards.

This short life cycle can still achieve beautiful results in your garden. Add some annual plants to the garden and replant their seeds if you wish to continue seeing the beautiful flowers year after year.

You can read my other article on how to start a flower garden from scratch here: How to Start a Flower Garden from Scratch (DIY Guide)

Alexander Picot

Alexander Picot is the principal creator of TheGrowingLeaf.com, a website dedicated to gardening tips. Inspired by his mother’s love of gardening, Alex has a passion for taking care of plants and turning backyards into feel-good places and loves to share his experience with the rest of the world.

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