Olives

Start from seed: Not recommended (use grafted trees or cuttings)

Optimum soil temperature for germination: Not applicable

Plant seedlings: March-May or August-September

Plant spacing: 4-6 meters (2m for hedging)

Days to maturity: 3-5 years to first fruit under ideal condition

Introduction

Olives (Olea europaea) belong to the Oleaceae family and are one of the oldest cultivated trees in the world. These evergreen trees, with their distinctive silvery-green foliage, not only provide beautiful ornamental value but also produce delicious fruit that can be processed for table olives or oil.

Archaeological evidence suggests that olives have been cultivated for over 6,000 years, with origins in the Mediterranean basin. Ancient civilizations in Greece, Rome, and Egypt valued olives not only as food but also for medicinal properties, lamp oil, and religious ceremonies. The olive branch has long been a symbol of peace and prosperity.

Olives were introduced to Australia with European settlement and have since become well-established in many regions with Mediterranean-like climates. Canberra’s cool winters and hot, dry summers provide suitable conditions for olive cultivation, although late frosts can sometimes affect production.

The olive tree forms a graceful, gnarled appearance with age, growing to a height of 8-10 meters if left unpruned. The small white flowers appear in spring, followed by green fruits that usually mature to black or purple, depending on the variety. Both the fruit and the oil are highly nutritious, containing beneficial monounsaturated fats, antioxidants, and vitamins.

Site and soil

Olives are well-suited to Canberra’s climate with cool winters, hot, dry summers and relatively low rainfall. They require full sun with at least 6-8 hours of direct sunlight daily and prefer a position sheltered from strong winds, particularly when young.

Prior to planting, prepare the soil by incorporating compost or well-rotted manure. Olives are very hardy and will survive and fruit in infertile, stony, shallow soils – even limestone. However, they will produce better with improved soil conditions. Olives like full sun and well-drained soil with a neutral pH (6.5-7.5). Good drainage is crucial as olives are susceptible to root rot in waterlogged conditions. Olives can tolerate temperatures as low as -9⁰C although -2⁰C will harm blossoms

For container growing, use a pot at least 60-75cm in diameter with good drainage holes. Fill with premium potting mix enriched with compost and a complete organic fertiliser. Container-grown olives require more frequent watering and feeding than those in the ground but can be productive for many years.

For details on preparing soil and pots, including the use of lime, dolomite, gypsum and fertilizers, please refer to the COGS guide to garden bed preparation.

Planting Seeds and Seedlings

In Canberra, it’s best to plant olive trees in autumn (March-May) or spring (August-September) to allow roots to establish before extreme weather. Growing olives from seed is not recommended as they don’t grow true to type and take much longer to fruit. Instead, purchase grafted trees or rooted cuttings from reputable nurseries.

When planting, dig a hole twice as wide as the root ball but no deeper. Mix the soil from the hole with some compost and 200grams of complete organic fertiliser. If drainage is an issue make a mound of this soil/compost mix in the bottom of the hole. Gently remove the tree from its container, loosening the roots if they appear circled or compacted. Place the tree in the hole or over the mound gently spreading the roots over the mound, ensuring the graft union (if present) remains above soil level. Backfill with the soil/compost mix, gently pushing it around the roots to eliminate air pockets.

After planting, water thoroughly and apply a 5-10cm layer of organic mulch around the tree, keeping it away from the trunk to prevent collar rot. For the first year, water regularly to establish the root system, particularly during dry periods.

For hedging, space trees 2 meters apart; for individual trees, allow 4-6 meters between each plant to accommodate their mature spread. Plants are generally not self-fertile so consider planting at least two different compatible varieties for cross-pollination and fruit set.

Cultivation

Olives prefer a Mediterranean climate with cool winters and hot, dry summers, making Canberra ideal for their cultivation. They require some winter chilling (temperatures between 0-9°C) for optimal flowering but are sensitive to severe or late frosts, which can damage flowers and reduce yields.

Water requirements vary with age and seasonal conditions. Newly planted trees need regular watering for the first 2-3 years to establish deep roots. Mature trees are quite drought-tolerant but benefit from deep watering during flowering (spring) and fruit set to improve yields. Reduce watering as fruits mature to enhance oil content and flavour.

Fertilise olives moderately, applying a complete organic fertilizer in early spring and in autumn after harvest. Avoid high-nitrogen fertilisers, which promote leafy growth at the expense of fruit production. A monthly foliar spray with seaweed solution; a mix of worm juice, seaweed and compost tea; or trace elements will help boost growth and resilience to pests and diseases.

Pruning is essential for maintaining tree health and productivity. Young trees benefit from tip pruning of lateral branches to encourage bushy central growth. For mature trees, prune after harvest to open up the canopy, allowing light and air circulation. Remove dead wood, water shoots, and branches that are too close to the ground. Remember that olives fruit on one-year-old wood, so avoid excessive pruning.

In Canberra, protect young trees from frost in the first few years by wrapping the trunk or using frost cloth during severe cold spells. As trees mature, they become more frost-tolerant but may still suffer flower damage from late spring frosts.

Harvesting

Olives typically begin producing fruit 3-5 years after planting, reaching full production after 7-8 years. Harvesting in Canberra generally occurs from mid-autumn to early winter (April-June), though timing varies with the variety and intended use.

For green table olives, harvest when fruits have reached full size but are still firm and light green to yellowish-green in colour. For black table olives, wait until fruits have fully ripened and developed their characteristic dark colour but are still firm. Olives for oil are usually harvested when 50-75% of the fruit has turned black.

Hand-picking is suitable for home gardeners with a few trees. For larger plantings, place a tarp under the tree and use a garden rake with plastic prongs to comb through the branches, dislodging the fruit. Avoid damaging the fruit, if possible, especially for table olives.

Freshly harvested olives are extremely bitter and inedible without processing. Table olives must be cured using brine, water, or lye methods to remove the bitter compound oleuropein. For oil production, olives should be processed within 24-48 hours of harvesting to maintain quality.

Expect yields to vary year by year, with some varieties showing alternate bearing patterns (heavy crop one year, lighter the next). Regular pruning, good nutritional management and consistent care can help minimize this tendency.

Problems

The best approach is to have a reliable Australian reference book to identify problems. Garden Pests, Disease and Good Bugs by Denis Crawford is recommended.

A general strategy to follow with any problem is to observe the plant carefully before taking action. Identify the problem then carefully consider the course of action. For example, with pest insects, you often can see a predator nearby. If you watch and wait the predator may deal with the problem for you. Beneficial predatory insects which feed on pest insects can be purchased from suppliers such as Bugs for Bugs. If the problem needs further action the above recommended book has suggestions. 

Cultural practices that help minimize pest and disease problems include maintaining good air circulation through appropriate pruning, harvesting all fruit to prevent pest buildup, and ensuring adequate nutrition without excessive soluble nitrogen.

Several pests and diseases can affect olives in Canberra, though they generally face fewer issues than in other regions:

Black Scale (Saissetia oleae): These small brown insects with an H-shaped ridge on their backs cluster on stems and leaves, sucking sap and secreting honeydew that leads to sooty mould. Heavy infestations can stunt growth, cause leaf drop, and reduce yields. Control with horticultural oils or insecticidal soaps during the crawler stage in spring.

Olive Lace Bug (Froggattia olivinia): A native Australian insect that feeds on the underside of leaves, causing yellow speckling on the upper surface. Severe infestations lead to leaf drop and reduced tree vigour. Monitor leaves in spring for emerging nymphs and spray affected areas with horticultural oil or organic insecticides if necessary. Prevent by ensuring trees are well fed and watered.

Frost Damage: Late spring frosts can damage flowers and young fruit, significantly reducing yields. Site trees in protected locations and consider using frost cloth for young trees or during flowering if late frosts are predicted.

Recommended Varieties

Olives are generally not self-fertile therefore different varieties need to be present for successful cross pollination. Several olive varieties perform well in Canberra’s climate:

Frantoio: An Italian variety widely grown in Australia for its excellent oil quality. Produces a fruity, aromatic oil and can also be used for table olives with a pleasant nutty flavour. Self-fertile but benefits from cross-pollination. Good cold tolerance.

Manzanillo: A Spanish variety valued as a dual-purpose olive. Produces medium to large fruit ideal for green or black table olives and reasonable quality oil. Early, heavy bearing and relatively frost tolerant. Low spreading tree easy to harvest. Benefits from cross-pollination with Frantoio.

Correggiola: Italian variety similar to Frantoio but with higher oil content. Produces excellent quality oil with fruity characteristics. Good cold tolerance and consistent bearer.

Leccino: Another Italian variety that performs well in cooler climates. Early ripening with good frost tolerance. Produces mild, sweet oil and is excellent as a pollinator for Frantoio.

Kalamata: Greek variety producing large, almond-shaped black table olives with excellent flavour. 

Verdale: popular dual-purpose variety. Medium sixed fruit of good quality on a low spreading tree that produces moderate yields, sometime biennial. 

UC13A6: large, almost round fruit with plenty of flesh. Heavy, regular bearing tree. 

Planting at least two compatible varieties such as Frantoio and Manzanillo will improve pollination and provide options for both oil and table olives. Choose varieties known for cold hardiness and early ripening to suit Canberra’s cool winters and risk of late spring frosts.

References

1. Bubel, Nancy. The New Seed-Starters Handbook. Rodale Books, 2018.
2. Crawford D. Garden Pests, Disease and Good Bugs. Australia: ABC Books; 2015.
3. Department of Primary Industries and Regional Development. (2024). Olive tree pests and diseases. https://www.agric.wa.gov.au/pest-insects/olive-tree-pests-and-diseases
4. Dove, Helena. Botany of the Kitchen Garden, Kew Publishing, Royal Botanic Gardens Kew, UK, 2023. 
5. Glowinski, Louis, The Complete Book of Fruit Growing in Australia. Lothian Publishing, Melbourne, 1991.