Cucumbers

Start from seed: October-November

Optimum soil temperature for germination: 18-33°C

Plant seedlings: November-December

Plant spacing: 40-60 cm

Days to maturity: 48-80 days

Introduction

Cucumber (Cucumis sativus) is a warm-season vegetable belonging to the Cucurbitaceae family, which also includes melons, pumpkins, and squash. These trailing plants with their crisp, refreshing fruits are popular garden vegetables worldwide.

Originally from India, where they have been cultivated for over 3,000 years, cucumbers spread to Europe via ancient trade routes and were later introduced to the Americas by European colonizers. Archaeological evidence suggests that cucumbers were being cultivated in Thailand as far back as 10,000 years ago, making them one of humanity’s oldest domesticated crops.

Cucumbers are valued for their crisp texture and mild, refreshing flavour. They are typically eaten fresh or pickled. Although there are specific pickling varieties, any cucumber can be pickled. With a high water content (approximately 95%), cucumbers are low in calories but provide vitamins K and C, potassium, and various antioxidants.

Site and soil

Cucumbers thrive in Canberra when planted in warm, sunny locations sheltered from strong winds. They require at least 6-8 hours of direct sunlight daily, though in the height of summer, they may benefit from light afternoon shade to prevent scorching.

Cucumbers prefer fertile, well-drained soil with a pH between 6.0 and 7.0. Being heavy feeders, they respond well to rich soil with high organic matter content. Prepare the soil thoroughly by incorporating plenty of well-rotted compost or aged manure and a complete organic fertiliser. Raised beds can be particularly effective in Canberra, as they warm up faster in spring and can provide better drainage.

For container growing, use a pot at least 30 cm deep and wide with excellent drainage. Fill with premium potting mix enriched with compost and slow-release organic fertilizer. Container-grown cucumbers will require more frequent watering and feeding than those grown in the ground.

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

Planting Seeds and Seedlings

In Canberra’s cool temperate climate, cucumbers should be planted after all danger of frost has passed, typically from mid-October to November. Soil temperature should be consistently above 16°C for successful germination.

Seeds can be sown directly into the garden or started indoors 3-4 weeks before transplanting. When direct-sowing, plant groups of 2-3 seeds, 1-2 cm deep, spaced 40-60 cm apart. Once seedlings emerge, thin to the strongest plant per group.

To get an early start or if you prefer using transplants sow seeds in pots. Biodegradable pots are handy because they minimize root disturbance when transplanting. Seedlings are ready for transplanting when they have developed 2-3 true leaves, typically 3-4 weeks after sowing.

Before transplanting, harden off seedlings by gradually exposing them to outdoor conditions over 7-10 days. Plant seedlings at the same depth they were growing in their pots. Water thoroughly after planting and apply a layer of organic mulch around plants, keeping it away from stems to prevent rot.

Cultivation

Consistent watering is crucial for success, particularly during flowering and fruit development. Water deeply at the base of plants, aiming to keep the soil consistently moist but not waterlogged. Irregular watering can lead to bitter fruits and blossom end rot.

Apply a balanced organic fertilizer when planting. Plants may need a side dressing of complete organic fertiliser when the first fruits begin to form. Feeding with a liquid seaweed or fish emulsion every 2-3 weeks during the growing season will help maintain vigorous growth. 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.

Cucumbers are available as bush and vining varieties. Bush varieties have a lower yield but are more compact. Vines grow up to 2 metres using tendrils, which are modified leaves, to grab onto supports, including other plants, to climb towards the sunlight. Therefore, providing support for cucumber vines is highly recommended. Trellises, stakes, or tomato cages allow vines to grow vertically, which saves space, improves air circulation, keeps fruits clean, and makes harvesting easier. Secure vines to supports with soft plant ties or clips as they grow.

The yellow flowers are day neutral so will blossom any time as long as it is warm enough. Regular harvesting encourages continued flower production. Remove any damaged or misshapen fruits promptly to direct the plant’s energy to new growth. If powdery mildew appears, improve air circulation and consider applying a milk spray (1 part milk to 9 parts water) to affected areas.

For bush varieties, pinch out the growing tips when plants have 5-7 true leaves to encourage bushy growth and more fruits. For vining types, allow the main stem to grow and pinch out lateral stems after they develop 2-3 fruits.

Harvesting

Cucumbers are generally ready to harvest 55-80 days after planting, depending on the variety. Pick fruits regularly to encourage continued production. The size at harvest depends on the variety and intended use:

Lebanese cucumbers are best picked when 10-12 cm long
Continental varieties can be harvested at 15-20 cm
Pickling varieties (gherkins) should be picked when 5-10 cm long
Apple cucumbers are ready when they reach tennis ball size and have a pale white skin

Use a sharp knife or secateurs to cut the stem rather than pulling fruits off the vine, which can damage the plant. Harvest in the morning when fruits are coolest and crispest.

Cucumbers are best used fresh, as their quality deteriorates quickly after harvest. They can be stored in the refrigerator for up to a week, wrapped in a paper towel or tea towel and placed in a perforated plastic bag or box to maintain humidity without causing rot.

In Canberra, the cucumber harvest typically continues until mid-autumn (March-April), when cooler temperatures slow growth.

Problems

There are numerous pests and diseases that can affect cucumbers. 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.

Practicing good garden hygiene, crop rotation, and maintaining plant vigour by providing adequate nutrients are key strategies for prevention.

Common issues include:

Wilting leaves during the day. It is common for the leaves to wilt during the day. As long as they perk up again in the evening it is not a problem. If not, you need to give them more water.
Powdery mildew: This fungal disease appears as white powder on leaves. Ensure good air circulation by proper spacing, avoid overhead watering, and apply milk spray (1 part milk to 9 parts water) or seaweed spray as a preventative measure. Select varieties that are less prone to powdery mildew.
Downy mildew: Yellow spots on leaf surfaces with grey-purple fuzz underneath. Manage by providing good air circulation, removing affected leaves, and applying organic copper-based fungicides if severe.
Cucumber Beetles: These yellow and black striped or spotted beetles feed on leaves and can transmit bacterial wilt. Control using row covers until flowering, hand-picking, or applying organic insecticides if infestation is severe.
Bacterial wilt: A serious disease transmitted by cucumber beetles. Affected plants suddenly wilt and die. No cure exists once plants are infected, so prevention through beetle control is essential. Remove and destroy affected plants and practice crop rotation.
Squash bugs: Gray-brown shield-shaped bugs that suck plant sap. Check undersides of leaves for bronze-coloured egg clusters and crush them. Remove adults by hand.
Vine borers: White larvae that tunnel into stems, causing wilting. Look for sawdust-like frass at entry holes. Cut out of vines and hill soil over the wound.
Aphids: These small sap-sucking insects can transmit celery mosaic virus. They often cluster on the undersides of leaves, causing distortion and stunting. Small populations can be controlled by washing them off with a strong stream of water or using insecticidal soap. Alternatively, neem oil or pyrethrin can be used. Beneficial predators like ladybugs and lacewings should be encouraged and can be purchased for release on the crop. Look for aphid mummies which are evidence that the aphid has been parasitised. Eggs can also be parasitised and will appear bronze in colour. Generally speaking, plants that are high in soluble nitrogen (nitrates and ammonia) are prone to attack by sap sucking insects. Ideally avoid using soluble nitrogen fertilisers and ensure plants have adequate trace elements. This can be achieved by using foliar sprays.
Two-spotted Mites: Tiny spider-like pests that cause stippled, yellowing leaves in hot, dry conditions. Increase humidity around plants by regular misting and apply insecticidal soap or neem oil for severe infestations.

Recommended Varieties

Most cucumber varieties have both male and female flowers on the same plant (monoecious). The female flowers appear as singles whereas the male flowers appear in clusters. Interestingly, cucumbers will produce fruits via parthenocarpy (i.e. without fertilisation) resulting in fruit with no seeds. These types of fruits are desirable because pollination via insects causes the fruit to be bitter due to a substance called cucurbitacin produced by the plant to deter herbivores. Some cucumbers have predominantly female flowers with the occasional male flower for pollination. Burpless cucumbers, sold in supermarkets, are produced via parthenocarpy therefore have no seeds and are bred to have thinner skins. Both these factors are thought to reduce burping.

Many cucumber varieties perform well in Canberra’s climate:

Lebanese: cylindrical, smooth, thin skinned

Muncher – burpless, tender skinned is a crunchy 15-20cm cucumber with excellent, flavour. Non bitter. Prolific and disease resistant.
Khassib – uniform crops of dark green, crisp fleshed fruits. Fruits 50 days from transplant.
Beth Alpha – spineless, thin-skinned, dark green with great flavour and disease resistance. Sets fruit without requiring pollination, greatly increasing the yield per plant.
Mini muncher – smooth skinned, productive mini-Lebanese cucumber

Continental: longer, slender, thicker and slightly textured skin

Marketmore 76 – Dark green cylindrical fruit with tapered ends and white spines that grows to 23cm by 6cm. Very productive. Excellent flavour. Excellent disease resistance.
Continental – Long, slender fruits up to 30 cm; good for both salads and cooking
Poinsett 76– deep green fruit, 20cmx6cm, with small white coloured spines. Sweet and refreshing to eat; good for slicing. Disease-resistant variety suitable for Canberra conditions; produces well in warm weather.
Spacemaster – Compact bush variety that produces 20cm green fruits. Good for containers.
Telegraph – long, slender, dark green fruit. Vigorous.
Armenian – Long, pale green, ribbed, burpless fruit with a refreshing flavour. Best picked when about 30cm in length. Technically a melon.

Pickling Varieties:

Piccolo – green pickler, producing over a long period.
Clarion – beautifully shaped pickling cucumber with excellent flavour if eaten fresh. Very uniform, cylindrical fruit.
Picklebush – Compact bush-type plant ideal for small spaces; prolific.

Other cucumbers:

Richmond Green Apple – Heritage Australian variety with round, green fruits and excellent flavour. Highly productive.
Crystal apple – Round, pale-skinned cucumber with crisp white flesh; unusual appearance and good flavour.
Quirk – seedless, burpless baby apple cucumber, 5-6 cm long with crunchy texture and sweet flavour. Good for eating and pickling. The plant is dark green and very compact with small leaves.

For Canberra’s climate, focus on varieties with good disease resistance, particularly to powdery mildew, which can be problematic in the region’s dry summers with cool nights.

References

Bubel, Nancy. The New Seed-Starters Handbook. Rodale Books, 2018.
Crawford D. Garden Pests, Disease and Good Bugs. Australia: ABC Books; 2015.
Dove, Helena. Botany of the Kitchen Garden, Kew Publishing, Royal Botanic Gardens Kew, UK, 2023.
Fanton, Michel and Jude. The Seed Savers Handbook. The Seed Savers Network, Australia, 1993.
Yates Australia. (2024). How to Grow Cucumber. https://www.yates.com.au/how-to-grow/cucumber/