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 for them and their situation. That's why we have an extensive range of garden and lawn fertilisers that are specially designed for all the different plant groups and their unique needs.

'Complete' fertilisers are fertilisers that contain the three main nutrients required for plant growth - nitrogen (N), phosphorus (P) and potassium (K). Nitrogen promotes green leafy growth, phosphorus encourages a strong root system and potassium promotes flowering and fruiting. Different plants need varying amounts of these main nutrients to help promote the best growth and flowering or fruiting. Many fertilisers also contain trace elements like iron, zinc, manganese and magnesium to encourage total plant health.  

All-purpose fertilisers, that contain a blend of the three main nutrients (nitrogen, phosphorus and potassium) 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 higher in nitrogen (to encourage green leafy growth) and are usually lower in phosphorus and potassium.

When planting seedlings, it's best to prepare and improve the soil beforehand with Yates Dynamic Lifter Soil Improver & Plant Fertiliser. It contains a blend of natural ingredients and provides gentle slow- release nutrients to seedlings as they establish. 

For leafy plants and seedlings growing in pots use Yates Thrive All Purpose Soluble Plant Food. It's as easy as mixing 1 - 2 spoonfuls of this soluble powder in a 9 L watering can and applying over the plants and surrounding potting mix.

For flowering and fruiting plants, it's best to use a fertiliser that is higher in potassium. 

To help your home-grown vegies and herbs feed you, you need to feed them! For tomatoes, vegetables and herbs growing in gardens, feed them every 6 weeks with Yates Dynamic Lifter Tomatoes, Vegies & Herbs. 

For vegetables and herbs growing in pots, a liquid fertiliser like Yates Thrive Natural Vegie & Herb Liquid Plant Food is ideal. 

Fruit trees need a special blend of nutrients that encourages both healthy green leaf and stem growth, as well as flowering and fruiting. 

For fruit trees growing in gardens, promote healthy growth and lots of flowers and fruit with Yates Dynamic Lifter Fruit & Citrus Plant Food Pellets. 

For fruit trees growing in pots, feed them every 1 - 2 weeks with Yates Thrive Citrus & Fruit Liquid Plant Food.

We often forget to feed indoor plants, but they'll be much more lush and healthy if fed regularly throughout the warmer months. An easy way to feed indoor plants is with Yates Thrive Plant Food Spikes Plants & Ferns. The spikes are simple to use - just push them into the potting mix - and they'll provide slow-release nutrients to the plant for up to 2 months. Alternatively, feed plants with Yates Thrive Indoor Plants & Ferns Liquid Plant Food. It's a concentrated liquid fertiliser that makes up to 150 L of plant food. 

Roses and other flowering plants do best with a complete fertiliser that's rich in potassium, with potassium being the key nutrient that promotes flowering. For flowering plants growing in gardens apply Yates Dynamic Lifter Roses & Flowers Plant Food Pellets around the root zone every 6 weeks during the growing and flowering seasons. For flowering plants growing in pots, a liquid fertiliser like Yates Thrive Rose & Flower Liquid Plant Food is ideal. Simply dilute and apply in a watering can. 

Many Australian native plants are sensitive to the concentrated nutrients found in some fertilisers. So, it's important to feed native plants with fertilisers that are safe for them. For Australian native plants growing in gardens, feed them with Yates Dynamic Lifter Plant Food & Soil Improver. 

For Australian native plants growing in pots, Yates Dynamic Lifter Liquid Concentrate is ideal. 

Orchids need a balance of nutrients to promote healthy green leaf growth as well as beautiful flowers. An easy way to feed orchids is with Yates Thrive Plant Food Spikes Orchids. Simply push a spike into the potting mix and the spike will provide the orchid with slow-release nutrients for up to 2 months. Alternatively, feed orchids with Yates Thrive Orchid Liquid Plant Food. It's a concentrated liquid fertiliser that makes up to 150 L of plant food. 

Cacti and succulents are hardy plants, but they'll be healthier and grow better if regularly fed. An easy way to feed potted cacti & succulents is with Yates Thrive Plant Food Spikes Cacti & Succulents. Simply push a spike into the potting mix and it will feed the plant with slow-release nutrients for up to 2 months. 

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 in the 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 added seaweed. These types of products will contain a complete range of nutrients and can be called fertilisers. 

Garden fertilisers are a source of plant nutrients. Depending on the type of fertiliser, they can be applied to the soil or the leaves or both. Fertilisers can be organic or synthetic, or a combination of the two (organic based).

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 usually 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 richer, more nutrient 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 the 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 can be given by applying Yates Leaf Greener Magnesium Chelate. 

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. The main symptom of iron deficiency is paler leaves with darker green veins. Iron deficiency can be corrected by applying Yates Leaf Greener Iron Chelate. Iron deficiency can also be common in alkaline soils. In this case, making the soil more acidic using Yates Sulfur Soil Improver Granules, can help give plants greater access to iron.  

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

Zinc is important for enzyme production and breaking down sugars.

Zinc and manganese deficiency can be common in citrus trees. To help fix deficiencies in both these nutrients, apply Yates Citrus Cure Zinc & Manganese Chelate. 

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, blood and bone meal and fish meal. 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. However, the nutrient content in some manures, like cow and sheep manure, can be relatively low and variable.

Pelletised Poultry Manures

Poultry manure is a good source of both nutrients and organic matter. It's best when poultry manure has been thoroughly composted before use, as raw manure has the potential to burn plants and contain harmful microorganisms. Yates Dynamic Lifter Soil Organic Plant Food & Soil Improver Pellets contains composted poultry manure (plus blood & bone, fishmeal and seaweed) and has been dried and compressed into easy-to-use pellets. The nutrients contained in Yates Dynamic Lifter are released slowly to the plants, and the organic matter helps improve soil health and quality.  

Fish Meal & Blood & Bone Meal

These are made from the waste products of fisheries and abattoirs and once composted provide gentle, slow-release feeding.

Green Manure Crops

This refers to leafy plants that are grown to be dug back into the soil. Green manure crops will often include legumes, such as peas, as they are able to convert atmospheric nitrogen into nitrogen for plant growth. When the plants are dug into the soil, they add both nitrogen and organic matter. 

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 can be recommended where odour is an issue (for example, feeding indoor plants), 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 nutrients, so it's important to apply 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.

Slow Release and Controlled-Release Fertilisers

As the name suggests, slow-release fertilisers release nutrients slowly to plants over weeks or months. This is achieved through special chemical formulations or the use of natural ingredients like poultry manure. Controlled release fertilisers also release nutrients to plants gradually over time and consist of a soluble NPK fertiliser particle surrounded by a protective, permeable coating. 

Liquid fertilisers can be based on organic or inorganic ingredients or a combination of both. They're ideal for feeding potted plants and usually contain fast-acting nutrients. Most can be applied to the soil or potting mix for absorption by the roots, and some can be applied as a foliar spray. Liquid fertilisers need to be reapplied more often than slow-release fertilisers.

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

Organic slow-release fertilisers are highly recommended for gardens and lawns as these will add nutrients and improve the soil.

Inorganic slow-release fertilisers are also recommended for gardens and lawns, particularly if odour is 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 lead to plant toxicity and symptoms can include leaf burning. Too little fertiliser won't provide the plants with enough nutrients so you won't see optimal 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), an application of sulfur can help reduce the pH. Apply Yates Sulfur Soil Improver Granules or Yates Soil Acidifier Liquid Sulfur.

If the soil pH is too low (acidic), an application of lime & dolomite can help increase the pH. Apply Yates Lime & Dolomite Soil Improver Granules or Yates Hydrangea Pinking Liquid Lime & Dolomite Fertiliser & Soil Alkaliser.

If the soil can't absorb water (is hydrophobic) then soluble nutrients can't move with the water down into the root zone. Click here for Water-Repellent & Hydrophobic Soil Treatment in Your Garden for info on how to identify and treat water-repellent soils.

Ensure plants are well watered prior to applying fertilisers. Don't fertilise dry soil or potting mix and water well after applying as per the label directions. 

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.