The olive tree only unfolds its Mediterranean flair with the right care. A crucial part of care is feeding olive trees at the right time with the right fertiliser. Discover how, when and with what to properly feed your olive tree.
Olive trees (Olea europaea) are native to the Mediterranean and parts of Africa and Asia. There, olive trees grow on poor, low-nutrient, stony soils. They are very hardy and quite undemanding. As we do not have a Mediterranean climate in the UK, it is most common to grow olive trees in pots. The soil volume and nutrient supply in pots are severely limited, so it is necessary to feed your olive trees regularly, even though they are slow-growing woody plants. When feeding olive trees, take into account the individual nutrient requirements of the Mediterranean tree: season, age of the olive tree and location determine the need for nitrogen and potassium. A well-timed application of fertiliser with the right dosage is essential for healthy growth.
- When to fertilise olive trees?
- Recognising olive tree deficiencies
- Feeding olive trees: what to use and how much?
- Feeding olive trees: recognising overfertilisation
When to fertilise olive trees?
Only fertilise olive trees during the growing season from April to September. When overwintering olive trees during the cold season, they do not need feeding. Repot olive trees every few years in fresh, nutrient-rich potting compost like our Plantura Organic All Purpose Compost, which contains lots of organic matter and the essential nutrients for a healthy olive tree. Plus, it is entirely peat-free. You can amend the potting compost with 20% sand or horticultural grit to increase drainage. No fertilisation is necessary for the first few months after repotting olive trees, unless deficiency symptoms appear. If your olive tree is not showing any symptoms of deficiency and is growing healthily, it is not necessary to feed it.
Young olive trees up to two years of age require very little, if any, fertilisation. Here, use a quarter to a third of the recommended dosage of fertiliser. Do not fertilise olive tree seedlings and cuttings.
Tip: fertilising young olive trees with potassium fertiliser in autumn can increase hardiness. The potassium helps harden off the branches, making them less sensitive to frost.
At a glance: when to fertilise olive trees?
- Feed olive trees in pots from April to the end of September
- Freshly repotted olive trees do not require any fertilisation for the first few months
- Fertilise in autumn with potassium fertiliser to increase winter hardiness
- Do not fertilise during winter dormancy
Recognising olive tree deficiencies
Even the undemanding olive tree can suffer from nutrient deficiencies. Here is how to spot nitrogen, potassium, calcium and phosphorus deficiencies as well as possible causes:
- Nitrogen deficiency: symptoms are yellowing leaves and very limited growth. If the olive tree has not been repotted or fertilised for some time, a nitrogen deficiency is likely.
Note: excessive watering and waterlogging at the roots can also cause these symptoms. So, before reaching for the fertiliser, check to see if water has been sitting in the pot for days or if the soil has been wet for a long time. Note: Excessive water and waterlogging at the roots can also trigger these symptoms. So before reaching for fertiliser, check whether the water has been standing in the container for days or whether the soil has been wet for a long time.
- Potassium deficiency: causes leaf tips to wither and eventually entire shoots to die.
- Calcium deficiency: olive trees prefer a slightly alkaline soil with a pH of 7 – 8. Calcium deficiency may occur if the pH is too low. This causes a yellowing of the leaves from the tips. The entire leaf gradually changes colour, and the veins lighten. Calcium-containing lime increases the pH while also providing the missing nutrient. But first, check the pH of the soil.
- Phosphorus deficiency: appears as a reddish colouration of the leaves, but this is extremely rare.
Feeding olive trees: what to use and how much?
Specialised fertilisers for olive and citrus trees have an optimal composition of nutrients for Mediterranean plants. They are usually sold in shops under the name of citrus feed. If you do not want to buy a specialised olive tree fertiliser, use a balanced NK fertiliser. Phosphorus is needed for flowering and fruiting but is usually present in sufficient quantities in high-quality potting composts. Ideally, the olive tree plant food will also contain trace elements, such as boron, iron, manganese, molybdenum and zinc. These trace elements are usually present in sufficient quantities in high-quality potting soils and will be enough until the next repotting.
Remember: olive trees that get a lot of light and heat grow faster than those that do not. As a result, these olive trees will consume more nutrients and require more fertiliser. The fertiliser type is also critical for determining how often to feed olive trees.
Summary: fertilising olive trees
- Specialised citrus feed is suitable for olives and other Mediterranean plants.
- Alternatively, use a universal fertiliser containing nitrogen (N) and potassium (K), and ideally other micronutrients.
- Fertilisation depends on age, location and fertiliser type.
Feeding olive trees with organic fertiliser
Using a primarily organic fertiliser can be extremely beneficial for light feeders like Mediterranean trees, as their nutrients are stored in the soil and gradually made available to the roots. Fertilisers with a high content of organic matter, such as our Plantura Liquid Citrus Food, have a gentle action. Applying such a liquid food not only benefits soil life but also there is also little risk of overfertilisation. Our citrus food is made from vegetable residues from the food industry to conserve the environment and valuable resources. Feed olives trees every 2 weeks with our liquid citrus food when watering. To do this, mix 15 to 25ml of citrus food with 5L of water and water the olive tree as needed.
Fertilising olive trees with mineral fertiliser
If the olive tree suffers from a severe nitrogen deficiency, mineral fertilisers, such as an NPK fertiliser, can quickly remedy the situation. Symptoms of severe nitrogen deficiency in olive trees include stunted growth and leaf drop after chlorosis. The nutrients are water-soluble in mineral fertilisers, making them directly available to the plant. However, we do not recommend using mineral fertilisers continually. The risk of overfertilisation is high with light feeders like olive trees, which can damage their sensitive roots. Water-soluble fertilisers are also at risk of being washed away by heavy watering or rain, polluting our waterways. Furthermore, mineral fertilisers are usually associated with high energy consumption and environmental costs.
Feeding olive tree with home remedies like coffee grounds
Coffee grounds are a daily waste product in many households that are high in nitrogen. Simply add a small amount of coffee grounds to the soil and work it in a little. Coffee grounds slowly release nitrogen to the olive tree. However, if you would like to fertilise your olive tree with coffee grounds, keep in mind that as they decompose, they lower the soil’s pH. To remedy acidic soil, make a feed with crushed eggshells and work into the soil. This will increase the soil’s pH.
Perhaps an unusual plant food for olive trees but you can use nail clippings and hair in the garden as a substitute for bone meal.
Plant teas, such as stinging nettle liquid fertiliser, are also used as home remedies. In addition to numerous micronutrients, liquid manures often contain significant amounts of nitrogen and can even be used undiluted against pests such as aphids (Aphioideae). Applying a comfrey feed (Sympthytum officinale) in autumn provides potassium to increase winter hardiness.
Feeding olive trees: recognising overfertilisation
Overfertilisation poses a much higher risk than deficiency. The main symptom of overfertilisation in olive trees is burnt leaves called nutrient burn. Shortly after fertilising, the leaves develop yellow-brown tips and edges that increasingly move inward and cause the whole leaf to wither. The leaves can also curl up. Usually, affected leaves quickly fall off. If there is a slight overfertilisation with nitrogen, the olive tree will develop long, thin shoots and mainly leaves but hardly form flowers. Repot the olive tree in fresh potting compost to remedy acute overfertilisation. Remove as much of the over fertilised soil from the root ball as possible.
Another important care measure for olive trees is proper pruning. Find out how and when to prune olive trees in our feature article.