There are three major elements that all plants require to some degree. Knowing which element does what can help with your selection of fertiliser.
- Nitrogen (N) – It mostly promotes leaf growth and is essential for the production of chlorophyll, which is the green pigment in leaves.
- Phosphorous (P)– This promotes root growth and also the overall development and growth of the plant.
- Potassium – (K) Assists with flower and fruit production
The ratio of each that a particular fertiliser has is called the NPK ratio and is shown on the product packaging.
There are other elements plants require, just in smaller amounts. These include Calcium, Sulphur and Magnesium and also Trace Elements, which are only needed in minute quantities.
Types of fertiliser
The ways fertilisers are packaged and the way you use them in your garden varies. Products like Dynamic Lifter and blood and bone come in large bags and are spread over the beds. Slow-release fertilisers come in little pellets which water permeates to release the nutrients. These are sprinkled around the base of plants. Liquid fertilisers are diluted with water, which you then pour over your garden. This is particularly handy for targeting individual plants or for fertilising pots.
What to use when
The most important time to fertilise is in spring, when the warming weather starts the growing season. Use a general purpose fertiliser then to give your entire garden a boost. Avoid the use of phosphorus-rich products on native gardens – feed them with a native-specific plant food instead. On lawns, use a specialised lawn fertiliser, which are high in nitrogen to promote leaf growth. Fruit, vegetables and flowering plants, require feeding at specific times to promote that growth. Use specialised fertilisers to suit them. For acid loving plants such as azaleas, camellias and gardenias, look for fertilisers specifically tailored to them.