Companion Planting Guide for Australian Gardens

Proven plant pairings, a simple companion chart, and what to keep apart

Companion planting is the practice of growing certain plants near each other so they benefit one another. Some combinations deter pests. Others improve soil, attract pollinators, or provide physical support. Gardeners in Australia have been using these pairings for generations, and many are backed by solid research.

This guide covers how companion planting works, the best pairings for Australian vegetable gardens, a quick-reference chart, what to avoid planting together, and the three sisters method.

How Companion Planting Works

Plants interact in several ways when grown close together. Understanding these mechanisms helps you make better planting decisions rather than following rules blindly.

Pest confusion

Many pest insects locate their target plants by smell. Strong-scented herbs and flowers planted among vegetables mask or confuse those scent trails. Basil near tomatoes, for example, makes it harder for whitefly to find their host plant. Marigolds release compounds into the soil that repel root-knot nematodes.

Nutrient sharing

Legumes (beans, peas) fix atmospheric nitrogen in their root nodules through a relationship with Rhizobium bacteria. Neighbouring plants benefit from this nitrogen, especially heavy feeders like corn and brassicas. After legumes are finished, cut them at soil level and leave the roots in the ground to release their stored nitrogen.

Physical support and shade

Tall plants provide shade for heat-sensitive crops. Lettuce grows longer into summer when shaded by corn or tomatoes. Climbing beans use corn stalks as a living trellis. Pumpkin vines sprawl beneath tall crops and act as a living mulch, keeping the soil cool and suppressing weeds.

Pollinator attraction

Flowering companions attract bees and other pollinators to your vegetable patch. Borage, lavender, and nasturtiums bring pollinators close to your tomatoes, cucumbers, and zucchini, improving fruit set. This matters most in urban gardens where pollinator numbers may be low.

Trap cropping

Some plants attract pests away from your main crop. Nasturtiums draw aphids away from beans and brassicas. The aphids cluster on the nasturtiums, which you can then remove or simply tolerate, while your vegetables stay clean.

Top 15 Companion Pairs for Australian Gardens

These pairings are reliable, well-tested combinations that work in Australian conditions.

1. Tomatoes and basil. Basil repels whitefly, aphids, and mosquitoes. Plant basil directly around and between tomato plants. Both enjoy the same warm conditions and watering schedule.
2. Carrots and spring onions. The strong scent of spring onions deters carrot fly, while carrots repel onion fly. Alternate rows of each for maximum benefit.
3. Beans and corn. Beans fix nitrogen that corn needs. Corn provides a climbing structure for pole beans. Plant corn first, then sow beans at the base once corn is 15 cm tall.
4. Lettuce and tall crops (corn, tomatoes, sunflowers). Lettuce bolts in full summer sun. Growing it in the dappled shade of taller plants extends your harvest by weeks.
5. Brassicas and dill. Dill attracts beneficial wasps that parasitise cabbage moth caterpillars. Let some dill go to flower among your broccoli, cabbage, and cauliflower.
6. Cucumbers and nasturtiums. Nasturtiums act as a trap crop for aphids and attract pollinators that improve cucumber fruit set. Plant them around the edges of your cucumber patch.
7. Strawberries and borage. Borage attracts pollinators and is said to improve strawberry flavour. It also self-seeds readily, so you only need to plant it once.
8. Pumpkin and radish. Sow radish around young pumpkin plants. Radish matures and is harvested before pumpkin vines need the space. Radish also helps break up compacted soil.
9. Potatoes and horseradish. Plant horseradish at the corners of your potato patch. It deters potato beetle and may improve disease resistance. Keep horseradish contained as it spreads aggressively.
10. Zucchini and marigolds. French marigolds (Tagetes patula) repel whitefly and nematodes. Ring your zucchini plants with marigolds for pest protection and colour.
11. Capsicum and chives. Chives deter aphids from capsicum. Their flowers attract hoverflies, which feed on aphids. Plant chives as a border around capsicum beds.
12. Eggplant and thyme. Thyme repels flea beetles, which chew small holes in eggplant leaves. Grow thyme as ground cover between eggplant stems.
13. Spinach and peas. Peas fix nitrogen and provide light shade for spinach during warm weather. Spinach acts as a living mulch beneath pea trellises.
14. Sweet corn and sunflowers. Sunflowers attract pollinators and beneficial predatory insects. Their tall stems provide a wind break for corn. Plant sunflowers on the south side so they do not shade the corn.
15. Garlic and roses (or fruit trees). Garlic planted beneath roses deters aphids. Cloves planted around the drip line of fruit trees may reduce fungal disease pressure. Harvest the garlic in summer without disturbing tree roots.

Companion Planting Chart

This quick-reference chart shows the most common companion relationships for popular Australian garden vegetables.

What to Avoid Planting Together

Some plant combinations cause real problems. These are the pairings worth avoiding.

Fennel and everything

Fennel is allelopathic, meaning it releases chemicals that inhibit the growth of most nearby plants. Grow fennel in its own pot or in an isolated corner of the garden, well away from your vegetable beds.

Tomatoes and potatoes

Both are nightshade family crops and share the same diseases, especially blight and verticillium wilt. Growing them close together increases disease pressure. If one gets blight, the other almost certainly will too.

Onions and beans/peas

Alliums (onions, garlic, leeks) inhibit the growth of beans and peas. The effect is well documented and significant. Keep these crop families separated by at least a bed width.

Brassicas and strawberries

Brassicas are heavy feeders that strip nutrients from the soil. Strawberries growing nearby often struggle with poor growth and reduced fruit. Keep them in separate beds.

Dill and carrots

Dill and carrots are closely related and can cross-pollinate. Dill may also inhibit carrot root growth. Use spring onions as carrot companions instead.

The Three Sisters Method

The three sisters is one of the oldest and most effective companion planting systems. It combines corn, climbing beans, and pumpkin (or squash) in a single planting that benefits all three crops.

How it works

• Corn grows tall and acts as a living pole for the beans to climb.
• Beans fix nitrogen in the soil, feeding the heavy-feeding corn and pumpkin.
• Pumpkin vines spread along the ground, shading the soil to suppress weeds and retain moisture. The prickly leaves also deter some pests.

How to plant three sisters in Australia

1. Build a mound about 30 cm high and 1 metre across. Space mounds 1.5 metres apart.
2. Plant 4 to 6 corn seeds in the centre of each mound in mid-spring (once frost risk has passed and soil is above 18 degrees).
3. When corn is 15 cm tall, sow 4 bean seeds around the corn stalks, about 10 cm away from the stems.
4. At the same time as the beans, plant 2 pumpkin or squash seeds at the edge of the mound.
5. Water the mound deeply twice a week. Feed with a balanced organic fertiliser every 3 weeks.

Use a tall-growing corn variety (not dwarf sweet corn). Plant climbing beans, not bush beans. Queensland Blue or Butternut pumpkin are good choices for the squash component.

Companion Planting in Small Spaces

Companion planting is especially useful in small gardens and raised beds where every square centimetre counts.

• Interplant herbs through your vegetable beds. Basil among tomatoes, chives around capsicum, dill through brassicas. Herbs take up little space and provide genuine pest-deterrent benefits.
• Use flowers as borders. Ring your beds with marigolds and nasturtiums. They look good, attract pollinators, and repel pest insects.
• Grow vertically. Train beans up corn or sunflower stalks. Use cucumber trellises with lettuce planted in their shade. Vertical growing doubles your use of the same ground space.
• Succession plant compatible crops. Follow early-harvested radish with beans. Follow peas with tomatoes. Each rotation benefits from what the previous crop left behind in the soil.

Common Companion Planting Mistakes

Avoid these common errors that reduce the effectiveness of companion planting.

• Planting companions too close. Companions still need their own space. Basil tucked 5 cm from a tomato stem will compete for light and water. Give each plant enough room to grow properly.
• Expecting miracles. Companion planting is one tool in your gardening toolkit. It reduces pest pressure but does not eliminate it. You still need to check plants regularly, water consistently, and maintain good soil health.
• Ignoring sun requirements. A shade-loving lettuce benefits from growing near corn. A sun-loving capsicum does not. Match sun preferences before matching companion charts.
• Forgetting rotation. Companion planting does not replace crop rotation. Move crop families to different beds each year to prevent disease buildup and nutrient depletion, even when using companion pairs.

Aromatic Herbs as Companion Plants

Herbs are the most practical companions for any garden. They take up little space, most are perennial (so you plant once), and their strong scent genuinely deters pest insects.

• Basil: Repels whitefly, aphids, and mosquitoes. Plant near tomatoes, capsicum, and eggplant.
• Rosemary: Deters cabbage moth and carrot fly. Plant near brassicas and carrots.
• Thyme: Repels flea beetles and cabbage moth. Good ground cover between larger plants.
• Chives: Deter aphids. The flowers attract hoverflies. Plant around fruit trees, roses, and capsicum.
• Dill: Attracts beneficial wasps and lacewings. Let it flower among brassicas. Keep away from carrots.
• Oregano: General pest repellent. Grows well as a ground cover in warm beds.
• Mint: Deters ants, aphids, and flea beetles. Grow in a sunken pot to prevent it taking over.
• Lavender: Attracts pollinators and repels moths. Plant along garden borders and paths.

Frequently Asked Questions

Related Guides

Pest Management Guide

Succession Planting Guide

How to Build a Raised Garden Bed