Oct 2, 2025
Week 2 – Plant Production and the Mechanics of Growth
An introduction to the biological and physical systems that govern plant development and soil performance within designed landscapes.
Technical
Understanding plant growth through internal transport, storage and physiological regulation.
This week introduced the fundamental physiological systems that govern plant growth, focusing on how vascular plants move water, nutrients and energy. We examined xylem and phloem as the primary transport tissues. Xylem functions through a combination of root pressure, capillary action and transpiration pull, transporting water and dissolved minerals upward from the root zone to leaves and growing tissues. Its lignified cell walls also contribute structural support, allowing plants to maintain rigidity under load.
Phloem operates through a pressure flow mechanism, distributing sugars, amino acids and hormones produced during photosynthesis from source tissues, primarily leaves, to sinks such as roots, developing buds and storage organs. The seasonal importance of this system was emphasised. During winter, carbohydrates are stored within the root system and woody tissues, enabling rapid early growth in spring before full leaf development and peak photosynthetic capacity. Disruption to either transport system, whether through compaction, drought or physical damage, directly limits growth rate, leaf expansion and overall resilience.
Understanding these internal processes provides a technical basis for assessing plant health in landscape contexts, particularly when diagnosing stress caused by poor soil structure, water imbalance or restricted rooting environments.
Cultivation, propagation and the technical assessment of plant quality.
Alongside physiology, the session explored plant production systems and the professional standards that underpin horticultural practice. Botanical naming conventions follow the structure Genus species ‘Cultivar’, ensuring precision and consistency in specification, procurement and communication across disciplines. Correct nomenclature is essential when selecting plants for performance characteristics such as disease resistance, growth habit or environmental tolerance.
We studied vegetative propagation techniques, particularly grafting and chip budding, which are used to combine desirable traits from different plants. Grafting involves uniting a scion with a compatible rootstock so their cambial layers align, allowing vascular tissues to fuse and function as a single organism. Chip budding follows the same principle but uses a single bud rather than a full scion, making it efficient for mass production. Both techniques rely on precise timing, cleanliness and biological compatibility to ensure successful vascular continuity.
The formation of adventitious roots was discussed as an indicator of plant adaptability. These roots emerge from non-root tissues, often in response to stress, pruning or burial, demonstrating a plant’s capacity for regeneration. We also examined indicators of nursery stock quality. Stem diameter relative to height was identified as a reliable proxy for structural robustness and vascular capacity, while poorly developed, unbranched root systems were highlighted as structurally weak, limiting anchorage and nutrient uptake once planted. These assessments directly inform plant selection decisions in landscape projects.
Soil as a dynamic medium shaped by texture, structure and load-bearing capacity.
The latter part of the session focused on soil science, reinforcing soil as a living and mechanically active medium rather than inert ground. Soil composition was described in terms of its ideal volumetric balance: approximately 45 percent mineral material, 25 percent air, 25 percent water and 5 percent organic matter, though these ratios shift depending on compaction, moisture and biological activity. Maintaining pore space for air and water movement was emphasised as critical for root respiration and microbial processes.
We studied the soil texture triangle, a classification tool that categorises soil based on the relative proportions of sand, silt and clay. Texture strongly influences drainage rate, water retention, nutrient availability and workability. For example, sandy soils drain freely but retain fewer nutrients, while clay soils hold water and nutrients but are prone to compaction and poor aeration. Understanding texture allows landscape architects to anticipate limitations and specify appropriate soil amendments or construction strategies.
The introduction of the California Bearing Ratio (CBR) connected soil biology to structural performance. CBR testing measures the strength of subgrades by assessing resistance to penetration, informing decisions around pavement thickness and load-bearing capacity. Although rooted in civil engineering, CBR values are highly relevant to landscape architecture, particularly where soft landscapes interface with paths, roads or hardstanding. Balancing structural adequacy with biological function is essential to avoid soil degradation while supporting designed loads.
Reflection
This session reinforced that plant health and landscape performance are governed by interconnected biological and physical systems. Understanding vascular transport, propagation methods and soil mechanics provides a foundation for making informed design decisions that support long-term resilience. For landscape practice, the lesson highlighted the importance of aligning plant selection, soil specification and structural requirements to ensure that growth is supported rather than constrained by design.
