Essential nutrients for plants and other requirements to consider

Just like us, plants need a variety of nutrients to grow, stay healthy, and thrive. While they are naturally equipped to obtain these nutrients from their environment — such as minerals from the soil, water from rainfall, and carbon dioxide from the air — they often require additional support to meet their full potential. This is where practices like fertilization and soil management come in, helping to supply missing nutrients and create optimal conditions for growth. Understanding what plants need and how they obtain it is key to keeping them strong and productive.

Essential nutrients

Macronutrients

Carbon, oxygen and hydrogen

These three elements are the foundation of all plant life, as they form the basic building blocks of carbohydrates, proteins, and other essential biomolecules. Carbon is absorbed from carbon dioxide (CO₂) in the air, oxygen comes from both water (H₂O) and CO₂, and hydrogen is also derived from water. These elements are crucial for photosynthesis and cellular respiration. Through photosynthesis, plants convert carbon dioxide and water into glucose, which serves as their energy source, and release oxygen as a byproduct.

We help plants by ensuring they have access to these resources: providing adequate air circulation for CO₂ absorption and water for hydrogen and oxygen. For example, growing plants in areas with good air flow and regular watering supports their growth.

While carbon, oxygen, and hydrogen are necessary for all plants, how much water a plant requires can vary. The amount of water needed depends on the type of plant, the climate, and the soil structure. For instance, desert plants are adapted to conserve water and can survive on minimal rainfall, while tropical plants may require consistent moisture to thrive. In terms of soil, well-draining soil allows water to move quickly through the root zone, which may necessitate more frequent watering for some plants. In contrast, clay-heavy soils can retain water longer, potentially reducing the frequency of watering. Understanding a plant’s water needs based on these factors is crucial for maintaining healthy growth.

Nitrogen, phosphorous and potassium

NPK, or NPK ratio, is often mentioned in relation to fertilisers. All three elements are always needed, but each one can be prioritised during certain stages in a plant’s life cycle so as to avoid nutrient deficiencies.

Nitrogen (N) is one of the most prevalent elements in plants, after oxygen, carbon, and hydrogen. It is especially important in the early vegetative and growth phases. During flowering and fruiting, lower nitrogen levels are ideal to avoid excessive leaf growth and to focus on flowering and fruiting. Nitrogen plays a key role in the formation of proteins, DNA, and chlorophyll, which is critical for photosynthesis. Without sufficient nitrogen, plants can exhibit slow growth, yellowing leaves, and poor overall health. To support plants, one can provide nitrogen through fertilisers when preparing the soil or at the start of the growing season. For leafy vegetables like lettuce or spinach, a fertiliser with a higher nitrogen ratio can promote lush, healthy foliage.

Phosphorous (P) is another abundant element found in the backbone of DNA, cell walls, and energy molecules like ATP (adenosine triphosphate), which plants use for energy transfer. Phosphorous is especially crucial for root development, seedling growth, flowering and fruiting. To support these processes, phosphorous is often added through fertilisers, particularly before flowering and fruiting.

Potassium (K) supports the plant through all stages, but particularly in stress management, water regulation, flowering and fruiting. It helps plants resist disease and plays a vital role in regulating the movement of water and nutrients throughout the plant. Potassium also aids in photosynthesis and the synthesis of proteins and starches.

To best help plants thrive, fertilisation should be done at key growth stages. Apply fertilisers rich in nitrogen when preparing garden beds or planting, especially for leafy vegetables. Use fertilisers with higher levels of phosphorous and potassium for plants that are focused on flowering, fruiting, or tuber growth. Alternatively, an all-purpose NPK fertiliser works well for a general balance in the garden.

Calcium, magnesium and sulphur

These secondary macronutrients play crucial roles in plant health. Calcium strengthens cell walls and regulates enzyme activity, magnesium is the core of the chlorophyll molecule and essential for photosynthesis, and sulphur is needed for protein synthesis and enzyme function. To help plants, one ensure that soil contains sufficient levels of these elements, often through soil amendments like lime or magnesium sulfate.

Micronutrients

Iron, Manganese, Zinc, Copper, Boron, Molybdenum, Chlorine and Nickel

These micronutrients, although required in smaller amounts, are vital for various enzymatic and biochemical processes in plants. Iron is necessary for chlorophyll synthesis, manganese activates enzymes involved in photosynthesis, zinc supports protein synthesis, and copper is involved in respiration. Boron helps with cell wall formation, molybdenum assists in nitrogen fixation, and chlorine helps with osmoregulation. One can help plants by ensuring they receive balanced micronutrient levels, often through trace element fertilisers.

Other considerations

Light

Light is essential for photosynthesis, the process through which plants convert sunlight into energy. Plants need light for producing sugars that fuel their growth, reproduction, and overall health. Ensure they receive adequate sunlight (note that some plants need full sun and some like shade), either through proper planting positions or using artificial grow lights in controlled environments. Interestingly, some plants, such as parasitic plants, do not engage in photosynthesis at all. Instead, these plants obtain their nutrients from organic matter or other plants, bypassing the need for sunlight.

Soil structure

Soil is a complex medium that provides plants with the necessary environment for growth. It is made up of five essential components: organic matter, living organisms, gas, water, and minerals. These elements work together to create a habitat that supports plant roots, while also supplying water, nutrients, and air.

While soil is the most common growing medium, alternatives such as coco coir (coconut husk fibers), vermiculite, and perlite are also used, especially in controlled environments like hydroponics or container gardening. These mediums, although not technically soil, can be effective for growing plants by providing the necessary support and aeration. Additionally, “soilless” potting mixes, which are often free from potentially harmful microorganisms, are popular for indoor and container plants.

Adding mulch, such as wood chips, straw, or leaf litter, can improve soil structure by conserving moisture, moderating temperature, and adding organic matter as it decomposes.

Living organisms in soil — like fungi, bacteria, insects, and worms — play a crucial role in maintaining soil and plant health. Introducing mycorrhizal fungi into the root zone during planting or transplanting, using organic mulches and compost to feed soil microbes and fungi and incorporating companion plants into garden planning can enhance soil biodiversity and fertility.

The mineral component of the soil is vital for plant nutrition and can be classified based on particle size. Clay particles, which are the finest, have a diameter of less than 0.002 mm. Due to their small size, clay particles are capable of holding a significant amount of water and nutrients but may also lead to poor drainage if soil structure is not managed properly. Silt particles are slightly larger, ranging between 0.002 mm and 0.05 mm, and have better drainage properties than clay, though they can still retain moisture and nutrients. Sand is the coarsest mineral particle, with a diameter between 0.05 mm and 2 mm. Sand improves soil drainage and aeration but has a lower capacity to retain nutrients compared to clay and silt. A balanced soil, often referred to as loam, contains a mix of sand, silt, and clay, providing optimal conditions for most plants (but not all).

Soil pH

Soil pH affects nutrient availability to plants. Most plants thrive in slightly acidic to neutral soils (pH 6–7), as nutrients are more soluble and accessible at these pH levels. We help plants by testing and adjusting soil pH as needed, often using lime or wood ash to raise pH in acidic soils or sulphur to lower pH in alkaline soils. For example, blueberries prefer acidic soil (pH 4.5–5.5), so amending the soil with sulphur ensures they get the nutrients they need.

Temperature

Temperature influences enzyme activity, seed germination, and overall plant metabolism. Most plants have an optimal temperature range for growth and extremes can stress or damage them. To help plants, ensure they are planted in environments with suitable temperatures, either by choosing the right varieties for the climate or using techniques like greenhouses to regulate temperature.

Life-cycle

The life cycle of a plant defines its growth, reproduction, and senescence stages, which vary between species. Plants can be classified into annuals, which complete their life cycle in one year, and perennials, which live for multiple years. Biennials take two years to complete their cycle.

Understanding a plant’s life cycle helps in providing the right care at each stage. One can assist by planting at the appropriate time for each species, such as sowing annuals in spring and ensuring perennials have proper winter protection. For example, annual vegetables like lettuce are planted in spring and harvested by fall, while perennials like asparagus return each year.

Additionally, many plants depend on effective pollination during their reproductive phase to produce flowers, fruits, or seeds. Encouraging natural pollinators like bees and butterflies, or manually pollinating in the absence of natural agents, can greatly enhance plant productivity.

It’s also important to consider where a plant is native to when planting it, as the climate and environmental conditions will play a significant role in its success. A plant that thrives in full sun in its native temperate climate may not perform as well in a warmer or more tropical region, where what is considered “full sun” might be much more intense. Similarly, plants that have evolved to withstand drought may require adjustments in watering schedules or soil care when grown in more humid areas. Understanding a plant’s native environment helps ensure that it is planted in the right conditions, which can significantly improve its growth and longevity.

Predators, pests and disease

Pests and diseases can severely impact plant health by damaging tissues, interfering with nutrient uptake, or spreading harmful pathogens. Pest management strategies can organic options like neem oil, biological controls like beneficial insects, and maintaining plant health through good care practices. For example, introducing ladybugs can help control aphid populations on roses, preventing significant damage to the plants. Additionally, leaving spiders in the garden can be beneficial, as they naturally prey on a variety of pests, such as aphids, caterpillars, and other insects that might otherwise harm plants. By fostering a balanced ecosystem, with natural predators, we can reduce the need for chemical interventions and promote healthier plants overall.

A Golden Orb Weaver spider made a web above my herbs.

References