Fertilize now for next season's fruit
Now is the best time to fertilize your fruit trees to get the best crops next season. Promote the growth of flowering buds with an Autumn application of Potassium in the form of ‘Sulphate of Potash’. Initiation of flower buds starts in Summer and Autumn, and is influenced by temperature and day lengths. Depending on the fruit type and variety, the flower initiation may occur over several weeks or months. You can encourage flowering growth by applying Potassium to the ‘drip line’ of the tree in Autumn.
On the packaging of fertilizers and growing media (potting mix) you will see a ratio against N (for Nitrogen), P (for Phosphorus) and K (for Potassium). Nitrogen encourages leafy growth, Phosphorus is for root growth and Potassium is for fruit and flowers. While a balance of all elements is required for fruit trees, the most important is Potassium.
There are several products available in garden centres that are high in Potassium:
For fruit trees grown in pots:
Use Tui Fruit & Flower Sulphate of Potash, as it is a water-soluble form, which can be applied with a watering can or sprinkled over soil. It is suitable for use for fruit trees grown in containers and in the ground.
You can also use wood ash from your home fire in the garden in small quantities (never use coal ash). It can either be composted or applied directly to the garden (this must be done in Winter otherwise it may burn the roots of the plants). Take care when using wood ash as it can make the soil very alkaline which is disliked by fruit trees – use a pH test and do not let the soil go over a pH of 7.5.