Plant nutrition
Plant Nutrition – Working With Nature, Not Against It
There are 17 essential nutritional elements required for a plant to live, grow and reproduce.
The good news? Most if not all already exist in your garden.
In most cases, there is no need to purchase synthetic or organic fertilisers. Healthy garden soils already contain everything plants require to produce strong growth, flowers and fruit — provided the soil ecosystem is allowed to function naturally.
Beyond their ongoing cost of manufacture, transport and repeated application, synthetic fertilisers disrupt the soil food web, damaging soil structure and reducing the diversity of microorganisms that are critical to long-term soil health. A living undisturbed soil is the foundation of resilient, self-sustaining planting.
The Law of Return – Nature’s Recycling System
The concept known as “The Law of Return”, coined by British botanist and agriculturist Sir Albert Howard (1873–1947), is a cornerstone concept of organic and regenerative gardening.
Its principle is simple:
What grows in the garden, stays in the garden.
In natural ecosystems, unused organic material is returned to the soil, where it decomposes and recycles nutrients back into the system. Eco-conscious gardeners replicate this process through composting, mulching and minimal disturbance.
Where garden neatness is important, plant material can be composted and later returned to beds as mulch. In wilder or wildlife-focused spaces, vegetation can be left standing over winter to provide structure, beauty and habitat, then cut down in spring and left in place — a method often referred to as “cut and drop.”
As plants mature, they naturally return the exact nutrients they require through leaf fall, root exudates and decomposition. A deciduous tree is a perfect example: the larger it grows, the more leaves it sheds, and the more nutrients are recycled to support its continued growth.
Plants Choose Their Own Nutrition
It is now well understood that plants actively direct and control nutrient uptake through complex interactions with soil microorganisms. Through the soil food web and wider terrestrial ecosystem, plants exchange sugars for nutrients, accessing what they need when they need it.
This is one of the great benefits of in-situ decomposition. The soil does not need feeding — the soil needs supporting.
A Fascination With the Unseen World
Eco-conscious gardening is both my profession and my passion. When I’m not in the garden, I turn to another fascination: soil regenerative microscopy.
Examining the unseen microbial world — bacteria, fungi, protists and more — reveals just how complex and cooperative soil ecosystems truly are. Plants are composed of billions of interconnected cells, each acting as a microscopic powerhouse working toward the same goal: growth, health and reproduction.
The 17 Essential Nutrients
Of the 118 elements on the periodic table, 94 occur naturally. Only 17 are considered essential to plant life, and these are almost always present in healthy garden soils and the atmosphere.
The Big Three
Carbon (C)
Oxygen (O)
Hydrogen (H)
These are absorbed as carbon dioxide (CO₂) and water (H₂O) and together make up around 96% of a plant’s biomass.
Macronutrients
The remaining six macronutrients are required in larger quantities:
Nitrogen (N)
Essential for leafy growth. Although nitrogen makes up 78% of the atmosphere, plants rely on soil bacteria and decomposition to make it available.
Deficiency: Yellowing leaves.
Phosphorus (P)
Supports energy transfer and root, flower and fruit development.
Deficiency: Stunted growth, reduced flowering and fruiting.
Potassium (K)
Regulates enzyme activity, water movement and gas exchange.
Deficiency: Leaf scorch, wilting and dead patches.
Calcium (Ca)
Critical for cell division and structural integrity.
Deficiency: Poor growth and malformed growing tips.
Magnesium (Mg)
Central to photosynthesis.
Deficiency: Green leaf veins with pale inter-veinal areas.
Sulphur (S)
Supports photosynthesis and respiration and can deter herbivory.
Deficiency: Yellowing of young foliage.
Micronutrients – Small Quantities, Big Impact
Micronutrients are required in smaller amounts but are no less essential. These include:
Silicon, chlorine, boron, copper, iron, zinc, manganese, molybdenum, nickel and sodium.
They support enzyme function, protein formation, respiration, photosynthesis, cell structure and natural plant defences. These nutrients are readily supplied by undisturbed soil and decomposing organic matter, highlighting the importance of composting and minimal soil disturbance.
For deeper exploration, Jeff Lowenfels’ “Teaming with Nutrients” Timber Press is an excellent resource.
Recognising Nutrient Deficiency
General signs of deficiency include:
Yellowing leaves (chlorosis)
Wilting
Leaf drop
Reduced growth
Some deficiencies are more subtle. For example:
Boron affects pollen formation and reproduction
Chlorine impacts growing tips
Silicon improves drought tolerance and resistance to grazing
A plant may appear healthy until environmental pressure reveals an underlying imbalance.
Let the Garden Do the Work
Plant nutrition is complex — but nature has been perfecting it for hundreds of millions of years. Our role as gardeners is simply to remove obstacles to biodiversity, not add products.
By:
- Increasing planting diversity
- Leaving herbaceous growth standing over winter
- Using cut-and-drop pruning
- Adding compost as spring mulch
…we support a living soil that supplies everything plants need, naturally and sustainably.
Healthy soil grows healthy plants — no fertilisers required.