Few fruits are as refreshing as a ripe watermelon, and by a stroke of luck, these bulbous fruits tend to grow best during the hottest parts of summer, making them an ideal way to cool down and stay hydrated when the worst of the heat kicks in during the Christmas season. However, while watermelons receive great benefits from a typically hot and sunny Australian summer, the soil they grow in usually needs some fertiliser if they are to grow as plump and juicy as you desire.

Choosing garden fertilisers for your watermelons can be tricky, as their nutrition needs are quite different from many other fruits and vegetables commonly grown in gardens. To keep you on the right track when picking out a suitable fertiliser for your melon patch, keep the following guidelines in mind:

High nitrogen fertilisers before flowering

Nitrogen is one of the most essential nutrients for the grown of any green plant, and watermelon plants gain particular benefit from high-nitrogen fertilisers during the early stages of their growth. High nitrogen content in your soil promotes the growth of your watermelon's roots, leaves and stems, giving the fruits themselves a solid foundation to grow on when the fruiting stage of the plant's development begins.

Low nitrogen fertilisers after flowering

Dainty yellow flowers appearing on your watermelon plant is your signal that the plant's fruiting stage is about to begin, and it's important to switch fertilisers as quickly as possible when this occurs. While nitrogen is essential for healthy plant growth, watermelon plants exposed to large amounts of nitrogen during their fruiting stages will pour more of their resources into growing thicker stems and larger leaves and will generally produce smaller, less succulent fruits as a result.

One the flowering stage beings, you should therefore switch to a fertiliser much lower in nitrogen and water your plants frequently to flush away excessive nitrogen content that remains in the soil from your previous fertilisation efforts. A fertiliser with around half as much nitrogen content as the one you used during early growth is typically ideal for fruit growth.

High phosphorous and potassium content after fruits have appeared

Phosphorous and potassium are almost as essential to plant growth as nitrogen and will promote the growth of large, ripe and juicy fruits on your watermelon plants. However, if applied before your fruits appear, high concentrations of potassium and phosphorous will promote large flower growth at the expense of stem growth, leading to very beautiful and completely useless plants with tiny fruits. Wait until the fruiting stage begins before adding a fertiliser containing high concentrations of these elements.