Why are my citrus flowers and fruit dropping? I have been told to feed with Sulphate of Potash for flowering, or is there more I can do to prevent this?

Hi, citrus will drop flowers and fruit will not set when trees are stressed. Citrus trees are also biennial bearing which means that they fruit every second year, this is especially true for mandarins. Citrus trees will also naturally drop fruit and hold on to what it can sustain. No amount of fertiliser will help this as it is nature taking its course. If your tree is newly planted and a couple of years old it is a good idea to remove the fruit that sets in the first couple of seasons so that the trees roots become well established and can support future fruiting. If your tree is in a pot make sure it is consistently watered in spring and summer, and that it does not dry out, is planted in a free draining quality potting mix and is in a pot that is big enough to sustain growth.

If your tree is established and has been in the ground for several years, here are a few things that can be done to help improve fruiting.

• Fertilise citrus in early spring (August, September) with a balanced fertiliser that has an NPK fertiliser ratio of 5-4-7 + trace elements. Citrus food contains potassium (potash) the K element, and will promote flowering and fruiting as well as ensure healthy growth.
  If you feed with a straight fertiliser, so just potassium, and not a balanced fertiliser, you will cause an imbalance in the soil. This can be more detrimental than not feeding your tree at all.
• Feed your tree again in late summer, early autumn, this will help with fruiting.
• The most common reason for fruit not setting is caused by the weather, rain and wet windy conditions at the time of flowering, bees do not work to pollinate the flowers. Make sure your tree is in a sheltered position and not exposed to wind.
• Another reason for lack of fruit set is the tree drying out and inconsistent watering in the growing season from spring to autumn. For an established tree water weekly, for newly established trees water every 2-3 days.
• Make sure your tree is planted in free-draining soil. If you have heavy clay soils they hold too much water in winter and dry out in summer.
• Mulch around the tree with a specialty mulch such as Tui Mulch & Feed, it helps keep weeds down, conserves soil moisture and also feeds the soil and the tree as it contains blood and bone as well as sheep manure.
• To keep your tree healthy and to stimulate root growth as well as help with flowering and fruiting apply Tui Seaweed Plant Tonic every 2 weeks. Mix 30ml in a 9 litre watering can and apply to the soil around your plant.

I hope this helps. The Tui Team.