How to organically fertilise phosphorus sensitive Australian native plants

Banksia ericifolia in Native Garden

Fertilising Australian native plants has sparked debate among gardeners for years. Historically, many believed these plants didn't need fertilising due to their evolutionary adaptation to grow in nutrient-poor soils. However, this myth has been debunked; In the garden, Australian native plants benefit significantly from feeding. While chemical fertilisers often pose risks due to high phosphorus levels, organic methods offer a safer alternative. By using compost, mulches, and specific organic liquid feeds, gardeners can nourish their native plants effectively and safely.

Australian native plants don’t necessarily need feeding but you can gain much more vigorous plant growth and stand out blooms from feeding your natives. Native plants have evolved different ways to seeking out scares nutrients in the soil and some have formed symbiotic relationships with soil and root node bacteria to aid them in doing so. When it comes to how and when to feed australian native plants the waters are muddy but let’s discover the best practices for organically feeding your Australian native plants and ensure your garden thrives.

The big phosphorus issue.

A lot of information about fertilising or feeding native plants revolves around using chemical fertilisers. Made using chemical processes often with mined minerals, They are environmentally damaging from source to application. They are bad for the earth and overuse can be disastrous for the health of your soil and you! Chemical slow release fertilisers can be used to kick start start young native planting to ensure vigorous growth. If you do choose to use a chemical based fertilisers for your Australian native garden be sure to use a native specific fertiliser as this product will be low in phosphorus and safe for all natives.

A few, but not all Australian native plant species are phosphorus sensitive or rather they have evolved to be very good at finding limited phosphorus in native soils. Plants within the Proteaceae family (Banksia, Grevillea, waratah) have developed specialised roots called “proteids”. These roots spread out in a fine mass which allow the plant to absorb nutrients from ancient nutrient depleted soil. So when you overload them with phosphorus they simply can’t handle it, they suffer and will likely die if high levels persist. On the other hand the majority of Australian natives are perfectly fine to live in richer soils containing higher levels of phosphorus.

Phosphorus sensitive natives include but are not limited to: Banksia, Grevillea, Acacia, Daviesia, Hardenbergia, Kennedia etc.

A rule of thumb for this is if it grows on coastal heathlands, sandy/sandstone soils or arid soils, generally it will be sensitive to excess phosphorus. Plants growing in rainforests or wetter areas are likely to be more tolerant of phosphorus in their diet. Herbaceous natives also seem to be more forgiving to higher phosphorus levels.

Through we are here to talk organic feeding, it’s good to have the background knowledge on phosphorus and why it is talked about so much when it comes to our natives. It’s also handy to know as because some of our organic inputs will still be far too high in phosphorus to use on a regular basis for our sensitive natives plants.

When to fertilise Australian Natives.

Feed or fertilise Australian native gardens twice a year, once in spring for vigorous growth , and again in late autumn for optimum flowering.
It’s a good idea to feed establishing plants for the first few years of life so they grow desirably, forming an attractive shape, then as they mature pull back on feeding as the plants are more capable of fending for themselves. Adding too much nitrogen to your native garden can cause plants to grow lots of leafy growth but reduce flowering and in some cases stop flowering all together. Remember less is more.

Organic Native fertilisers

Organically feeding Native plants, as with all organic feeding, is about feeding the soil and creating healthy soil, alive with microorganisms. In turn healthy soil will support the plants within your native garden. The best way to build build soil is by using organic matter such as compost, manures, mulch, garden clippings, etc. The key is to use a wide rage of different inputs. Diversity creates soil biodiversity. Although, some organic materials may be too intense to use directly on native plant species. When feeding plants organically its best to take a less is more approach, meaning, go slow and don’t overload your natives.

For the purposes of this guide we are working on the basis that you don’t know or are not sure if your plants are phosphorus sensitive and the information provided below works for both phosphorus sensitive and non phosphorus sensitive plants. By using organic inputs to feed your garden you are making a much safer choice for the environment as well as your individual plants.

Liquid feed - Yes!

Watering can filled with Native safe organically homemade liquid feed.

Organic liquid feeds can be purchased or made at home.
When purchasing an organic liquid feed they’re generally brown in colour and will be made of seaweed, fish waste, bone meal or other organic matter, always check the packaging to make sure they’re safe for natives. Seaweed solutions are also perfectly safe for application on natives. They love it.

Making Your own liquid feed could come in the form of making a weed tea or compost tea, you could get fancy and make a native prunings or clippings tea.

Creating a tea from fresh lawn clippings is a perfect option as it will be higher in nitrogen and potassium and lower in phosphorus.

The process of making liquid feed teas at home can be a simple as filling a bucket with your fresh organic matter or some compost or manure then filling the rest with water and letting it sit for a week or two, you can also add a fish tank bubbler to accelerate the process by oxygenating the water. Then strain the liquid, dilute with water and apply to the soil around your plants.

Mulches and Garden Clippings - Yes!

Eucalyptus Mulch

Wood chip mulches, leaf litter and native plant prunings will build excellent soil as they decompose over time. This is the best and safest way to feeding native plants. The key is to use a wide rage of materials to support a wide rage of microbial life. When dressed or mixed with compost the decomposition of the material can be accelerated building your soil and feeding your native plants quicker.

For a cleaner, neat look. native mulches like tea tree or eucalyptus mulch as well as pine bark mulch are suitable for native plants. For newly established native gardens use aged mulches to avoid nitrogen drawdown.

Compost - Yes / Sparingly

Compost

Home made compost has to be the best for building healthy rich soil, used throughout a native garden you’ll see amazing results. For the home gardener it’s hard to produce enough compost for your own garden, so you’re likely to have no other option but to use it sparingly. but if you do produce lots, be careful not to overload plants. It can be hard to tell what nutrient make-up your home made compost consists of so spread your compost evenly across the garden not just directly under plants.

Bone Meal - No

Bonemeal

Bonemeal, also known as blood and bone is a blend of finely and coarsely ground animal bones and by-products from slaughterhouses. It functions as a slow-release organic fertiliser, delivering phosphorus, calcium, and a minor amount of nitrogen to plants. The key thing is that It is high in phosphorus and in frequent or excess amounts is not suitable for Australian native plants.

Manures - Yes & No

Holding a scoop of well rotted cow manure

Manures make a great soil conditioner perfect for building healthy soil, but different animal manures vary greatly in their nutrient content and not all are suitable for the native garden. Any manure used in a native garden should be well rotted prior to application.

👍 Cow & Sheep - Well rotted cow or sheep manure is good for natives due to being lower in phosphorus due to a grass fed diet of the animal.

🤷‍♂️ Horse & Goat - Suitable but only when used very sparingly.

❌ Pig - Not suitable for natives.

❌ Chicken - Not suitable for long term use on natives as it is very strong in nutrients and high in phosphorus. Allowing live chickens for forage and poop through a native landscape is good for aerating the soil and depositing small amounts of nutrients into the soil.

❌ Cats & Dogs - Not suitable for use in garden at all.

👍 Rabbit & Guinea-pig - Yes, safe for natives.

👍 Native Animals - Perfect! If you somehow have access to native animal scat then what better could there be! naturally native animal manures are perfectly suited to native plants. Don’t remove native animal manures from natural landscapes, It is vital to the health of our native bushland

Wood Ash - Yes / Sparingly

Small twigs being burnt for native feed.

Wood Ash like that from a fireplace can add a boost in potassium which benefits native plants flowering.
The Australian landscape is no stranger to fire and many native species like Banksia’s have evolved to require fire for germination so it is no surprise that wood ash is generally safe for native gardens.

Again use sparingly and dispersed evenly across the garden not just under plants can see major benefits for your native blooms. An application once a year is more than enough.

To be sure your wood ash is loaded of potassium burn the ash from younger, thinner branches like you would use as kindeling.

Plant clippings, Chop & Drop - Yes

Pruning

The easiest way to feed you’re natives is to chop and drop plant clippings and prunings. Like mulch it will break down over time releasing the nutrients and making them available to the plants. For the best quickest result make sure your clippings are small so they will break down much quicker. Again diversity of inputs will create biodiverse soil so change it up!

Plant Acacias - Yes

Acacia terminalis

The Australian native species of Acacias are leguminous plants which are able to absorb nitrogen from the atmosphere and have formed a symbiotic relationship with a specific root node bacteria. Together they are able to store and fix the nitrogen for the use of the plant itself while they are alive and when they die the nitrogen becomes available to the plants around the acacia. As home gardeners we can cheat the system by pruning our acacias and scattering the clippings. Chop and drop people! As the plant material breaks down it releases the nitrogen into the soils.

Adding some lovely acacias and harvesting their leaves for your native garden you will naturally help boost nitrogen levels within your soils promoting strong vigorous growth within the garden.

Beware that acacia’s need very little extra fertilising, adding too much extra nitrogen to their soil could disrupt the natural nitrogen fixing process.

Though not entirely necessary, fertilising and feeding Australian native plants in your native garden can produce promote ideal growth and blooms. The safest and easiest way to feed your plants is by using organic inputs alone. Organically feeding plants with any of the inputs listed will be beneficial to your native garden, but remember less is always more when it comes to feeding natives. By using compost, mulches, and organic liquid feeds, gardeners can create healthy soil that supports thriving native gardens. Understanding the specific needs of different native species and applying organic fertilisers appropriately will ensure your Australian native plants bloom beautifully and maintain their natural resilience. Embrace organic feeding practices to nourish your native garden sustainably, safely and effectively.