What Are Garden Fertilisers & Why Do I Need to Feed My Plants?

All plants are different and need varying amounts of nutrients in a format that is suitable to them and their situation. That's why we have an extensive range of garden fertilisers that are specially designed for all the different plant groups and their unique needs.

All-purpose fertilisers are best for young seedlings and leafy plants like ferns, palms, conifers, grasses, and strappy leafy plants such as Yuccas and Lomandras. All-purpose fertilisers can be high in nitrogen and are low in phosphorus and potassium.

For leafy plants growing in gardens use Yates Dynamic Lifter Soil Improver & Plant Fertiliser.

For leafy plants and seedlings growing in pots use Yates Thrive All Purpose Soluble Plant Food.

Avoid using all-purpose fertilisers when plants are flowering and fruiting phase.

For vegetables and herbs growing in gardens use Yates Thrive Natural Vegie & Herb Organic Based Pelletised Plant Food.

For vegetables and herbs growing in pots use Yates Thrive Vegie & Herb Liquid Plant Food.

For fruit trees growing in gardens use Yates Thrive Natural Citrus & Fruit Organic Based Pelletised Plant Food.

For fruit trees growing in pots use Yates Thrive Citrus & Fruit Liquid Plant Food.

For a ready-to-use format use Yates Thrive Indoor Plants & Ferns Liquid Plant Food Drippers; or for a liquid concentrate format, where the liquid concentrate is mixed with water, use Yates Thrive Indoor Plants Liquid Plant Food.

For flowering plants growing in gardens use Yates Thrive Natural Roses & Flowers Organic Based Pelletised Plant Food. 

For flowering plants growing in pots use Yates Thrive Roses & Flowers Liquid Plant Food.

For Australian native plants growing in gardens use Yates Dynamic Lifter Soil Improver & Plant Fertiliser.

For Australian native plants growing in pots use Yates Dynamic Lifter Liquid Concentrate.

For a ready-to-use format use Yates Thrive Indoor Orchid Liquid Plant Food Drippers; or for a liquid concentrate format, where the liquid concentrate is mixed with water, use Yates Thrive Orchid Liquid Plant Food.

For cacti and succulents growing in pots use Yates Thrive Plant Food Spikes Cacti & Succulents.

Seaweed is not a fertiliser. It doesn't contain the essential macro-nutrients - Nitrogen, Phosphorus, Potassium - which make up a fertiliser.

However, seaweed contains various beneficial nutrients and compounds that can enhance the plant's ability to withstand stress and adapt to changing environmental conditions. It can also stimulate root development and improve overall plant health.

You can apply a seaweed solution when transplanting or in the lead up and during an extreme weather event, such as a heatwave or frost. Apply early morning or late afternoon. It can be applied over the foliage and around the root system of the plant. Allow the product to dry on the leaves.

Some fertilisers do contain seaweed and such a product will have an N:P:K, and is termed a fertiliser. 

Garden fertilisers are a source of plant nutrients. Depending on what type you get, they can be applied to the soil or to the leaves. Fertilisers can be organic or inorganic based, or a combination of the two.

Plants need nutrients for healthy growth, flowering and fruiting. When the nutritional needs of plants are not met, plants can get symptoms of deficiency. To avoid this issue, garden fertilisers can be added to the soil to replenish essential nutrients.

In the wild, there is a constant cycle where soil organic matter (in the form of dead animals, animal faeces, leaf litter, etc.) is constantly being returned to the soil. This cycle improves the soil quality and replenishes the soil nutrients that plants need to grow.

Plants in their natural environment are more adapted to the soil and other environmental conditions, and so don't need extra support. They also don't need peak performance.

Gardens are unnatural environments where we often grow non-native plants and hybridised plants in degraded soil. 

Non-native (exotic) plants often originate from areas with good quality and fertile soil. They are not adapted to poor quality and low-nutrient local soil. Also, hybridised plants don't occur in nature.

Our garden's soil is not wild soil where organic matter is constantly being replenished. Even Australian native plants won't grow, or at least won't thrive, in degraded soils. As plants grow they use up soil nutrients and these need to be replaced.

Plants growing in poor quality and low nutrient soil will have slow growth, poor or lack of flowering and fruiting, and reduced plant health. By improving our soils and using garden fertilisers we are providing our plants with rich soil so our plants look and perform at their best.

Nutrients are elements that plants primarily get from the soil and somewhat through their leaves. They can be divided into major and micro nutrients. 

Carbon, oxygen and hydrogen can be obtained from the air and water but all other elements are dissolved in water and taken up by the plant's roots or, to a limited extent, by its leaves.

Nutrients needed in large amounts are known as major-nutrients or macro-nutrients. Nutrients needed in relatively smaller amounts are known as minor-nutrients, micro-nutrients, or trace elements.

Major-nutrients include nitrogen, phosphorous, potassium, calcium, magnesium and sulfur.

Minor-nutrients include iron, boron, manganese, molybdenum and zinc.

Nitrogen is an essential part of the proteins in plant cells. It is most important for leaf growth and is a necessary part of the green pigment chlorophyll.

Phosphorus is important in cell formation so is most needed by the growing parts of the plant. Phosphorus promotes the development of seedlings, root growth, flowering and formation of fruits and seeds.

Potassium assists in photosynthesis and is helpful to the plant's 'food factory'. It assists the plant's overall strength, water uptake and disease resistance, and improves the quality of flowers, fruits and seeds.

Calcium forms the cell wall structure. It is available in lime, superphosphate and gypsum but is quickly leached out by heavy rain. Watch out for blossom end rot (sunken areas on the base) on fruits, especially tomatoes. This is caused by a lack of calcium or by poor uptake of calcium which may be a result of unreliable watering.

Sulphur forms part of plant protein. Deficiency is relatively rare because sulphur is found in most plant foods.

Magnesium is important in photosynthesis because it is present in chlorophyll. New leaves have first call on this nutrient and, because magnesium moves very readily through the plant's system, deficiency is most often evident as yellowing of the older leaves. A magnesium boost is supplied by an application of Epsom Salts dissolved in water.

Trace elements are essential to plant growth but are only needed in minute quantities. It is important to remember that the symptoms of excessive application may be as severe as the symptoms of deficiencies.

Iron is important for enzyme function and is essential for chlorophyll production.

Manganese is part of enzymes for respiration, photosynthesis, and nitrogen utilization.

Zinc is important for enzyme production and breaking down sugars.

Copper is important for enzyme function and production.

Boron is important for cell strength and utilisation of sugars.

Molybdenum is an important component of certain enzymes.

Organic-based fertilisers come from things that were once living. Examples include animal manures (composted poo/faeces), blood and bone meal, fish meal, and green manure crops. Organic-based fertilisers are highly recommended because they add nutrients and improve the soil at the same time.

Animal Manures

These are excellent for improving soil structure when used in relatively large quantities, but their nutrient value is relatively low and vary variable, depending on the type of manure and the animal's diet.

Pelletised Poultry & Sheep Manures

Manure has been compressed into pellets and dried so that, as the pellets break down, the nutrients release gently over a long period. Yates Dynamic Lifter Soil Improver & Plant Fertiliser is a good example.

Fish Meal & Blood & Bone Meal

These are made from the waste products of fisheries and abattoirs and provide a very gentle, long-term feeding.

Green Manure Crops

A leguminous plant, such as peas, is grown (because it can trap atmospheric nitrogen) and dug into the soil after flowering. The use of green manure crops is limited by the space available.

Inorganic fertilisers are fertilisers that come from non-living materials including minerals (e.g., limestone) or are manufactured from a variety of processes and ingredients (i.e., synthetic, e.g., Urea). These can be highly concentrated and are used in specific situations.

Inorganic fertilisers are recommended where the smell is an issue, where soil chemistry needs to be changed (e.g., soil pH), or when faster results are needed.

Powdered & Granular Fertilisers

These come in different formulations to suit different types of plants. These usually contain a high proportion of soluble nitrogen so can be very damaging to roots unless there is plenty of water available to assist the nitrogen to dissolve. Always supply to moist soil and water well after application.

Water Soluble & Liquid Fertilisers

These types of complete fertilisers are designed to dissolve rapidly in water and are applied directly to the plant by a watering can or a hose-spray attachment.

Controlled-Release Fertilisers

These are relatively new developments in fertilisers and they have revolutionised fertiliser application in production nurseries. They consist of a soluble NPK fertiliser particle surrounded by a protective coating.

Liquid fertilisers can be organic or inorganic based and are ideal for pot plants and for fast-acting nutrients. Most can be applied to the soil for fast absorption by the roots, and some can be applied as a foliar spray for faster action to leaves. Liquid fertilisers need to be reapplied more often than slow-release formats.

Slow-release fertilisers can be organic where they break down over time with water and temperature; or inorganic where they are released by either water or temperature, or both. Some Slow-release fertilisers are are a combination of organic and inorganic fertilisers.

Organic slow-release fertilisers are highly recommended for gardens and lawns where the smell is less of an issue. These will add nutrients and improve the soil.

Inorganic slow-release fertilisers are also recommended for gardens and lawns where smell can be an issue. Some can last a very long time (up to a year), provide a high concentration of nutrients, and are convenient.

Too much fertiliser can poison plants and send them into toxicity. Too little fertiliser won't provide the plants with enough nutrients so you won't see results.

Even with the best fertilisers, if the soil pH is too high or too low for your plant, then the plant can't access those nutrients. Click here for more info on What is Soil pH & How to Fix It.

If the soil pH is too high (alkaline) apply Yates Soil Acidifier Liquid Sulfur.

If the soil pH is too low (acidic) apply Yates Hydrangea Pinking Liquid Lime & Dolomite Fertiliser & Soil Alkaliser.

If the soil can't absorb water, then the soil nutrients can't move from the water and be taken up by the roots. Click here for Water-Repellent & Hydrophobic Soil Treatment in Your Garden for info on how to identify and treat water-repellent soils.

Ensure the plants are well watered prior to application. Don't fertilise dry soils. To avoid damage to feeding roots, make sure that the soil is moist by watering before and after the application.

For slow-release fertilisers, water in well after application. Don't apply fertiliser to a garden or lawn and then neglect to water it very thoroughly, especially in hot weather. It is inevitable that leaf burn will occur with careless applications of fertiliser on lawns.