Green Design: Creating Healthy Sustainable Spaces
Green design, also known as sustainable design, seeks to create environmentally friendly, healthy spaces with a positive social impact. It encompasses the planning and designing of buildings, landscapes, and other areas to reduce energy consumption, pollution, and waste generation.
Understanding the purpose of green design solutions is vital in making informed decisions about the most suitable plants for your project. Whether it’s developing biodiverse site furnishings to cool outdoor areas, capturing rain with a green roof, or trapping air pollutants with a green wall, it’s important to consider the purpose that leads to a successful and sustainable green design project.
Conducting and analyzing on-site research and similar projects provides valuable insights into what works best for a specific location. Consideration of the architectural context, including the building's sun and shad exposure and the impact sunlight has during different seasons, is crucial. It’s important to note that climate variations (e.g., light and temperature) can significantly differ between ground level and the green rooftop of a skyscraper. To this point, you should consider both horizontal and vertical climate variations.
Plant Growth and Survival
Evapotranspiration, the movement of water from surfaces to the atmosphere through evaporation and transpiration, is vital for plant growth and survival. Transpiration represents 95-99% of the total plant water uptake and loss. It involves water absorption by the roots, eventually releasing vapor through the leaf's pores (stomata) with a small portion passively lost through the leaf cuticle.
In dry regions, plants have developed well-formed strategies to survive droughts. These include leaf shedding, stiff leaves (sclerophylly), and forming a thick waxy cuticle. Some plants have sunken pores and shallow circular root systems for water absorption, like the laurel, holm oak, wild olive, myrtle, and strawberry tree.
Plant adjustments for wet conditions optimize photosynthesis, gas, and nutrient absorption through specialized leaves that lack a protective layer and pores on the undersides. These adapted leaves directly absorb water, nutrients, and gases. Chloroplasts concentrate in the well-lit upper leaf surface, and in some wetland plants, roots are reduced in size and mainly serve as an anchoring function. Absorptive root hairs may be absent, and, under flooded conditions, specific species undergo rapid shoot growth, allowing shoots to reach above the surface of the water for gas exchange.
Light is a Critical Component
Sunlight is crucial for plant growth through photosynthesis. Maximum growth depends on exposure to natural and artificial "grow" lights and can vary greatly between plant species. Consider plant-specific light needs and a mix of shade and light-tolerant plants for successfully lush and biodiverse projects.
Plants face challenges balancing photosynthesis and water loss in dry and high-light conditions, due to increased free radical generation formed during photorespiration. Free radical scavengers in drought-tolerant plants serve as defense mechanisms, offsetting the damaging free radicals and protecting cellular components like DNA, cell membranes, and proteins.
C3 plants, like roses, maples, and wheat, account for about 85% of plant species and rely on C3 photosynthesis for efficient growth. This process captures CO₂ through RuBisCO, and is highly effective in cooler climates and moderate sunlight. However, in hot and dry conditions, energy loss occurs due to photorespiration. This causes plants to lose a lot of water because stomata open during the hottest parts of the day.
On the other hand, C4 plants, like corn, sugarcane, and some grasses, have unique reshaping to thrive in warmer and sunnier habitats. They utilize C4 photosynthesis, which minimizes photorespiration by concentrating CO₂ around RuBisCO. As a result, C4 plants maintain high photosynthetic rates while preserving water, making them ideal for water conservation in landscaping projects.
Finally, CAM plants like succulents and cacti have a different photosynthetic method. They open their stomata at night and store CO₂ as malate, a four-carbon compound. During the day, when stomata are closed, CAM plants utilize stored carbon for photosynthesis; as a result, the plants conserve water in dry conditions making them fit for xeriscaping and drought-tolerant garden designs.
When designing outdoor green spaces, it’s important to understand factors like climate, plant species, irrigation systems, building configuration, and sunlight patterns. These factors will provide the difference between an acceptable or a thoroughly successful green design project.
By keeping the factors presented here in mind, landscape architects and designers can ensure resilient and low-maintenance green solutions that will work with nature instead of against it. Understanding plant adjustments and responses to environmental conditions can help you make informed decisions and create beautiful, visually appealing, and sustainable outdoor spaces.
By Dr. Anna Zakrisson