Evolutionary Changes in Hedging Plants

By Chandler Harrod

Plants have long fascinated scientists with their diverse structures and adaptations. From the towering redwoods to the delicate orchids, the world of plant anatomy is one of great importance. In this blog, we will delve into the intriguing world of hedging plants, exploring their physiological mutations over time and the scientific evidence that sheds a light on their evolution. Like all living organisms, plants are composed of cells, tissues, and organs. However, their unique feature is the ability to produce their own food through photosynthesis, a process that converts sunlight, water, and carbon dioxide into energy-rich molecules.

The primary organs of a typical plant include roots, stems, and leaves. Each organ performs specific functions crucial for the plant’s survival and growth. For instance, roots anchor the plant in the ground, absorb water and nutrients from the soil, and store reserve substances. Stems provide support, transport water, nutrients, and sugars throughout the plant, and serve as the site of new growth. Leaves are the main sites of photosynthesis, facilitating gas exchange and capturing sunlight for energy production.

Introduction

Hedging plants, also known as hedgerows or living fences, have been an integral part of human civilization for centuries. These plants are selected and manipulated by humans to create dense, interwoven barriers for privacy, protection, or demarcation. Over time, hedging plants have evolved and adapted to the changing environmental conditions and human needs, resulting in fascinating physiological changes. Evolutionary adaptations in hedging plants primarily involve genetic variations that confer specific traits or characteristics beneficial for hedging purposes.

Genetic Adaptations

Scientific studies have revealed that hedging plants undergo genetic mutations that contribute to their unique growth patterns. These adaptations that can affect traits such as branching, leaf morphology, and growth rate, leading to the development of hedging-specific varieties. For example, certain mutations may promote denser branching, resulting in a more effective and impenetrable barrier.

Denser Branching

Hedging plants have been selectively bred and cultivated to promote denser branching. This adaptation results in a compact growth habit and a more effective hedge for privacy or protection. Through careful selection and propagation of individuals with naturally denser branching patterns, humans have shaped the genetic composition of hedging plant populations to produce these desirable traits. English Yew is an example of a tree that has been used for centuries to form a dense hedge.

The English yew is an iconic hedging tree known for its dark green, needle-like foliage. It has been a popular choice for centuries, particularly in formal gardens and estates. English yews possess a natural tendency to produce dense growth, making them ideal for creating tall, impenetrable hedges. These trees are highly adaptable to pruning and shaping, allowing for precise control over their form.

Increased Lateral Bud Development

Regular pruning, a common practice in maintaining hedging plants, stimulates the development of lateral buds along the stems. Lateral buds give rise to new shoots, resulting in a fuller and denser hedge. This response to pruning is not a mutation but rather a physiological adaptation of the plant to the removal of apical dominance (the inhibition of lateral bud growth by the apical bud).

Thicker and Stronger Stems

Hedging plants subjected to regular pruning or trimming often exhibit thicker and stronger stems compared to their wild counterparts. This response is an adaptation to mechanical stresses induced by pruning. Regular pruning leads to increased deposition of lignin and other structural compounds, reinforcing the stem and making it more resistant to breakage or damage.

One example of such adaptation would be the European beech trees, known for their dense foliage and smooth gray bark. They have been extensively used for hedging purposes. Through selective breeding and cultivation, beech trees have been shaped into formal hedges with tightly packed leaves and a compact growth habit. The natural tolerance of beech trees to pruning and their ability to regenerate from old wood make them well-suited for hedging applications.

Tolerance to Shading

Hedging plants often grow in close proximity to each other, resulting in reduced light availability for the lower parts of the hedge. Over time, hedging plants have adapted to tolerate shading conditions by developing larger and more efficient leaves in the upper canopy. This adaptation enables them to capture and utilize available light more effectively.

One example of a tree that has become shade tolerant through its use as a hedge is the common hornbeam (Carpinus betulus). Hornbeam is a deciduous tree native to the UK and various parts of Europe. While it can grow into a tall tree, the hornbeam has been widely used and shaped as a hedge in the UK for centuries.

Through regular pruning and management practices, the hornbeam has developed adaptations that enhance its shade tolerance. Dense growth habit allows the tree to capture and maximize the available light in shaded conditions. The leaves of the hornbeam are small, ovate, and have a serrated edge. This leaf structure is an adaptation to tolerate shade, as it increases the surface area for light absorption while reducing the overall leaf size. The small leaf size helps optimize light capture and allows the tree to efficiently photosynthesize in reduced light conditions. Hornbeam hedges are typically pruned regularly to maintain their desired shape and density. This management practice, coupled with the slower growth rate of hornbeam trees, helps them adapt to shade by conserving energy and allocating resources efficiently.

The shade tolerance of common hornbeam hedges has made them popular choices for hedging in the UK. They provide privacy, windbreaks, and visual appeal in gardens, parks, and other landscape settings, even in areas with limited direct sunlight.

The common hornbeam’s ability to thrive in shaded environments as a result of its use as a hedge demonstrates the remarkable adaptability of plants and their capacity to evolve specific traits to suit different ecological niches.

Drought Resistance

In regions with limited water availability, hedging plants have evolved adaptations to withstand drought conditions. These adaptations may include modifications in leaf morphology, such as reduced leaf surface area or specialized structures like waxy cuticles or stomatal modifications that help reduce water loss through transpiration. Some hedging plant species may also have deeper root systems to access water sources at lower soil depths.

Conclusion

It is important to remember that the specific adaptations of hedging plants can vary depending on the species, local environmental conditions, and human selection practices. While the examples mentioned above provide a glimpse into the range of adaptations observed in hedging plants, there are many more intricacies and variations in the evolutionary history of these plants that continue to be studied by scientists.