What are achenes?

An achene is a small, dry, single-seeded, indehiscent fruit, meaning it does not open to release its seed. The seed is attached to the pericarp at a single point, distinguishing achenes from other fruit types.

Achenes differ in size, shape, and color based on plant species. Dandelion achenes are tiny and fluffy, whereas sunflower achenes are larger and robust. These traits aid in effective seed dispersal, ensuring plant survival and growth.

Common Types of Achenes

Although achenes differ widely in their forms, they can be grouped based on origin and structure. Here are a few notable examples:

1. Sunflower Achenes

One of the most recognizable examples of achenes comes from the sunflower (Helianthus annuus). Each seed in the center of a sunflower head is actually an achene. The tough outer shell not only protects the seed inside but also aids in its dispersal.

With over 92 million metric tons produced annually, sunflower achenes are a significant agricultural product, valued for their nutritional content. People often munch on them as snacks or use them to produce sunflower oil, which accounts for about 10% of global vegetable oil production.

A cluster of sunflower achenes showcasing their unique structure.

2. Dandelion Achenes

Dandelions (Taraxacum spp.), often seen in gardens and fields, have a unique feature in their achenes. Each achene is equipped with tufts of hair, known as pappi, that allow them to be carried away by the wind.

This adaptation helps dandelions effectively spread their seeds. For instance, a single dandelion can produce up to 200 seeds in one flowering cycle, contributing to their successful growth in diverse environments.

Dandelion achenes displaying their fluffy seed heads ready for dispersal.

3. Strawberry Achenes

Interestingly, the tiny seeds on the outside of a strawberry (Fragaria spp.) are also achenes! Each of these achenes contains a seed and connects to the fleshy part of the fruit.

This unique positioning not only gives strawberries their delightful appearance but also plays a role in attracting animals for seed dispersal. As animals consume strawberries, they help spread achenes across different areas, increasing the plant’s chances of survival.

Strawberry displaying its achenes clustered on the fruit's exterior.

3. Hemp Achenes

Cannabis sativa also produces achenes that range in size and color. Some can be pale while others are dark with vein-like lines.

The petals and sepals on hemp are extremely reduced with their inflorescence being mostly bracts that are stacked on top of each other. Inside each of these bracts is an ovary with two protruding stigmas that are often referred to as "hairs". Once pollen comes in contact with these stigmas, it will bore its way all the way down the stigma into the ovary and eventually develop into an achene.

Hemp achenes with dark vein-like patterns

Significance of Achenes in Nature

Achenes are crucial for plant reproduction, remaining viable in harsh conditions and germinating into new plants when conditions improve.

For example, studies have shown that achenes from dandelions can remain dormant for more than 5 years in the soil. This resilience allows plants to take advantage of favorable conditions when they arise.

By learning about achenes and their functions, we can better appreciate their role in ecosystems and the biodiversity they support.

Final Thoughts

Achenes are unique, diverse, and essential components of many flowering plants. Their distinct structure and ecological significance make them worthy of our attention. From sunflowers to dandelions and strawberries, achenes highlight the wonders of nature's design.

Next time you encounter these small yet remarkable fruits, take a moment to appreciate their vital role in continuing the cycle of life.