Plant Life Balance

How to give your plants a proper feed

Just like we humans need key nutrients to survive, so do our foliaged friends.

Image: Dr Excelsior’s Photography | Rowan Jackson

So you’ve kept your latest leafy friends alive for a few months, settled into a good watering routine and figured out exactly how much sun each needs. You may have also named them and set up dedicated Instagram pages for them (just us?). Congratulations, you’re ready for the next exciting level of plant care – plant feeding! A healthy, correctly-fed plant not only looks better, but is much more resilient to stress and pest attacks. Plants with good nutrition will also display larger leaves, flowers and fruit than those with little nutrition.

The good news is, dishing out the correct type and amount of plant food isn’t nearly as tricky as trying to feed a howling human baby (…just us again?) – with a good understanding of what to look out for and how to administer it, feeding your plants is a walk in the park. We sat down with the experts from Greenlife Industry Australia to chat all things dirt and plant nutrition.

Plant and soil nutrition: why it is so important?

Just like humans need key nutrients to survive, so do our foliaged friends. These nutrients can be broken into two main groups:

  • Macronutrients – those required in larger quantities and which are vital to plant health; and
  • Trace elements – which also play an important role, though required in much smaller amounts.

Thankfully, there is a wealth of information and plant specific foods our there to make this plant food-pairing simple for all levels of gardener.

What’s the relationship between soil and plant health?

Soil provides plants much more than just a place to put their roots – soil is comprised of minerals, organic matter, water, air spaces, and is also home to a host of microorganisms vital to sustained plant nutrition. Poor soils are typically low in nutrients and unable to hold water, which is also critical for overall plant health. Soil structure and pH also play key roles in how a soil holds and releases nutrients.

When it comes to feeding plants, it is all about supplying those key macro and micro nutrients to the plant. The feeding of soils, however, is more about building soil structure as well as nourishing the soil microbiome (bacteria, fungi, etc.) found within healthy soils. This is generally achieved using organic plant foods and composts.

How can you test soil to check for quality?

Having a dig and looking, feeling and smelling your soil can be the best way to start to this process. A sweet-smelling, dark rich loam full of worms will present the senses a vastly different experience to a dry, sandy soil with no visible life or an anaerobic wet clay.

That being said, it is important to know what plants you are intending on growing, as this will affect the desired attributes of your soil.

There are two simple tests that you can quite easily do yourself at home, or by visiting your local garden centre with a sample:

  1. Testing pH: The first is to test the pH of your soils. This will identify the acidity or alkalinity of your soil, and can be the first step in fixing any nutritional problems. For example, an acid-loving plant grown in alkaline soils can show deficiencies, even if the nutrients are present in the soil, as the soil’s pH can lock down nutrient availability to the plant. Inexpensive pH test kits are available from your garden centre.
  2. Soil Texture Test: Soil texture testing is another one you can do to work out the percentages of sand, silt and clay in your soils. Knowing your soil texture is useful to ascertain how well it will hold water and nutrients. A simple ribbon test will give you a basic guide.

How can you spot nutrient deficiencies on the plant itself? 

Plants can show deficiencies in their leaves with discolouration and/or patterns. Deficiencies can also manifest in other growth abnormalities in leaves, flowers and fruit.

It’s not always easy to diagnose deficiencies visually in plants, as they can present differently in various plant species. If your plant is displaying a deficiency, take a sample to your local garden centre for proper diagnosis.

What kinds of plant nutrition products are out there? What’s the main differences we need to be aware of?

There are two main categories of plant nutrients that you can purchase for your plants:

  1. Organic nutrients come from plant and animal wastes (e.g. animal manures; blood and bone; fish meal, worm castings & composts) and are a great source of not only nutrients, but are also  beneficial for soil structure, microorganisms and soil moisture retention. Organic fertilisers are also inherently slow release as nutrients need to break down to be released.
  2. Mineral fertilisers are much more concentrated, and contain mineral salts blended in different combinations to suit different plants type needs. They are typically much faster in their availability to plants but care needs to be taken to avoid burning plant roots, especially when used in pots.

Aside from this basic organic/mineral fertiliser breakdown, there are three main categories of plant fertilisers:

  • Water soluble – Supplied as liquid or powder and diluted into a watering can or syphon mixer on a hose. These are normally the most readily-available form of nutrients for plants to take up, and are a good option when you are after fast results. One downside is that they require more frequent application – typically fortnightly.
  • Slow release – These can be organic in their ingredients or comprised of mineral salts (or both) that require further soil processes to make them available to plants, thus slowing their release. Release time is typically around 8 weeks.
  • Controlled release – these are fertilisers with a delay mechanism such as coating that allows for prolonged release of nutrients over many months. The benefit of this is a constant release of nutrients without the leaching effects of regular soluble foods.

Any final hints and tips?

  • Care should be taken with mineral fertilisers when applying to pots, as the salts can easily burn roots if used incorrectly.
  • Organic fertilisers with are often not as popular for indoor plants due to its earthy smell, especially when derived from items such as fish waste; manures or blood and bone.
  • Seasons have a great effect on nutrient requirements for plants. Plants that are actively growing (i.e. during the warmer months) are going to be in need of more nutrients than a deciduous tree over winter. Each season might also bring about differing nutrient requirements as plants set flowers and fruit. Care needs to be taken with selecting the food type and its timing for best results.

Got a specific plant food question, or want someone to take a look at your soil? Head down to your local Plant Life Balance accredited nursery and have a chat with the experts.

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