Nitrogen is needed by leafy plants and veg like lawn grass and cabbages. If you wanted to feed your lawn or your leafy veg, look for a plant food that has a higher number next to the N initial than the P and K numbers. For example N30 : P5 : K5.
Potassium helps plants produce more flowers and fruit. When your ornamental plants, fruit and veg start to flower, this is the time to switch from a high nitrogen to a high potassium feed.
Phosphate helps plant roots develop. Therefore, it’s ideal to have high phosphate feed if you’ve recently moved an established plant or planted a tree.
Now that the nutrient puzzle has been demystified, it’s just a case of understanding why certain plants need feeding and how best to do it as well as when to do it.