Fertilising Plants 101

Unlike outdoors, your indoor plants can only absorb nutrients from the soil around them and from the supplements you give them. Fertilizer is a fantastic technique to replenish depleted nutrients that are necessary for plant growth and wellness.

What exactly are fertilisers?

Fertilisers, in whatever form they take, are fundamentally concentrated versions of nutrients that are required for plant growth and function. The three most important nutrients in fertiliser are nitrogen (N), phosphorus (P), and potassium (K), which should be labelled as a ratio, such as 6-1-4. 

Why NPK?

Nitrogen (N) encourages the growth of foliage.

Phosphorus (P) will aid in the development of healthy roots.

Potassium (K) promotes flowering.

Micronutrients such as calcium, magnesium, and iron, which play different roles and are present in lesser levels than N, P, and K, are also included in some fertilisers. 

Is it necessary to fertilise my plant?

Short answer yes.
Long answer indoor plant soils over time gets depleted of nutrients as the plant consumes them or they are rinsed away during watering. Fertiliser will take their place to keep your plants healthy and thriving, similar to a vitamin boost.

While newly potted plants and those that thrive in low-light environments may not require fertiliser for a while, plants that produce flowers or plants that grow quickly can benefit from additional fertiliser. 

Which type of fertiliser is best?

Fertilizers occur in a variety of forms, including liquids, granules, tablets and sprays. Because tablets and sticks do not properly disperse nutrients throughout soil when the plants are potted, liquid and slow-release fertilisers are better for indoor plants.

Liquid fertilisers are designed to be placed to your watering can so you can simply control how often your plant receives nutrients and stop when it doesn't, such as during the winter months.

Slow-release Fertilizers take time to break down and release nutrients into the soil. Some of them are coated in a thin shell to aid release nutrients over time, which means you don't have to worry about reapplying fertiliser as frequently, but this might also make them more expensive than the others.

How to fertilise you plants?

The method you use to fertilise your plants will vary depending on the type of fertiliser you use, and while there are some basic guidelines below, you should ALWAYS follow the instructions on the product itself.

There are 2 options, the first is to add it to the top layer of the soil to boost growth throughout the growing season (spring/summer). Avoid contacting the foliage with the fertiliser if possible, as this might cause burning. The second option is to add fertiliser into the soil mix before planting a plant.

Again there are two options which are mixing soluble or liquid fertilisers with water and then feeding the plant. This is a good approach to supply nutrients directly to the plant, avoid contact with the foliage. The second option is Foliar feeding, which involves pouring diluted fertiliser directly onto leaves, however not all liquid fertilisers are suitable for foliar use.

When to fertilise?

The optimum time to fertilise your indoor plants is during the growing season, which is spring and summer. This is when your plants will be using the most nutrients. However, the frequency with which you fertilise is determined by the type of fertiliser you use and the plants that you own. Plants that grow quickly, will benefit from more frequent fertilisation than plants that grow slowly.

Despite the best of intentions, too much fertiliser can be too much of a good thing and harm your plants. Please ensure you follow the dilution instructions of your product and if in doubt dilute further.