Maximizing Garden Growth with Companion Planting: An Organic Approach

Why Bother?

Bigger harvests, fewer sprays, happier soil. Planting the right mates side-by-side lets nature handle pest patrol while your crops feed each other underground.

Thinking beyond pairings: designing a companion-friendly garden

Companion planting works best when you look at the whole garden, not just plant-to-plant combinations.

Height and layering
Tall plants like corn, sunflowers, or trellised tomatoes can provide light shade and wind protection for smaller, more delicate crops. This is especially useful in hot Australian summers.

Root depth and competition
Plants with different root depths often grow better together. Shallow-rooted lettuce can sit happily above deeper-rooted carrots or tomatoes, sharing the same bed without competing heavily for nutrients.

Airflow and sunlight
Good airflow reduces fungal issues and stress. Even “good companions” can struggle if planted too closely. Always consider how wide and dense each plant will become at full size.

Crop rotation and succession planting
Rotating plant families each season helps break pest and disease cycles. Succession planting — sowing quick crops like radishes or spinach between slower growers — keeps soil covered and productive without overcrowding.

Quick Myth-Busters

Claim	Verdict	Aussie reality check
Basil stops fruit-fly on tomatoes	❌	Needs a hedge of basil plus exclusion bags to make a dent.
Marigolds kill nematodes	✅*	Works when grown as a season-long border then chopped in.
Carrot + onion combo prevents pests	✅	Smell masking cuts carrot-fly damage by ~40 %.

*Verified in NSW DPI glass-house trials (2023).

Trap crops and beneficial insect magnets

Some plants don’t just grow food — they actively shape what happens in your garden.

Trap crops
Trap crops are planted to attract pests away from your main harvest. For example:

Nasturtiums can draw aphids away from brassicas
Mustard greens may attract cabbage moths
Marigolds can lure pests while also confusing others with scent

These plants are best grown just outside or at the edges of beds, where pests can be monitored and managed easily.

Beneficial insect magnets
Flowering plants like dill, alyssum, calendula, and yarrow attract predators such as ladybirds, lacewings, and parasitic wasps. These insects help keep pest populations in check naturally and are most effective when flowers are available across multiple seasons.

The 2025 Companion Chart (Top 20 Staples)

Main Crop	Best Mates	Keep Apart	Why It Works / Pests Repelled
Tomato	Basil, Marigold, Borage	Corn, Fennel	Scent confuses thrips; marigold roots suppress nematodes.
Capsicum / Chilli	Basil, Onion, Parsley	Fennel	Onions deter aphids; basil improves flavour.
Carrot	Leek, Rosemary, Spring Onion	Dill	Alliums mask scent → fewer carrot flies.
Cabbage family	Dill, Mint, Nasturtium	Strawberries	Dill lures parasitic wasps; nasturtium traps aphids.
Lettuce	Radish, Marigold, Chive	Celery	Radish distracts flea beetles; marigold repels green peach aphid.
Pumpkin / Zucchini	Sweet Corn, Beans (Three Sisters)	Potato	Beans fix N; corn gives windbreak.
Potato	Calendula, Bean family	Tomato, Pumpkin	Calendula traps potato beetle; beans add nitrogen.
Spinach / Silverbeet	Strawberry, Celery	Potato	Strawberries sprawl, shading soil to keep roots cool.
Pea	Carrot, Turnip, Cucumber	Onion family	Carrots gain N; tall peas provide dapple shade.
Fruit Trees	Chive, Nasturtium, Comfrey	Grass under canopy	Nasturtium distracts codling moth; comfrey is chop-and-drop mulch.

Easy companion planting combos for Australian gardens

Warm-season companions (spring–summer)

Tomatoes + basil + marigold
Corn + beans + pumpkin (the “Three Sisters” style grouping)
Capsicum + onions + parsley
Zucchini + nasturtium + dill

Cool-season companions (autumn–winter)

Broccoli + dill + lettuce
Carrots + spring onions + rosemary nearby
Spinach + peas + calendula
Cabbage + thyme + chamomile

These combinations work best when spacing and sunlight needs are respected. Companion planting supports growth — it doesn’t replace good garden planning.

Aussie Climate-Zone Tweaks

Tropics & Sub-tropics (Darwin, Brisbane): Swap cool-season brassicas for Asian greens and snake beans.
Temperate (Syd, Melb, Perth): Late-summer sowings of marigold still flower before first frost.
Cool / Alpine (ACT, Tassie): Dwarf corn keeps the Three Sisters inside a frost-free window.

4-Step Bed Design

Map sunlight & wind – tall crops on the west edge.
Layer root depths – shallow leafies → medium root veg → deep miners.
Alternate scent & colour – confuses pests, attracts predators.
Feed the soil first – mix in TurboDirt Water-Only Super Soil or dust on a handful of Root Roids for instant mycorrhizal allies.

Using native plants to support companion planting

Companion planting doesn’t stop at the veggie patch. Including Australian native plants nearby can significantly improve garden resilience.

Native flowering shrubs and groundcovers provide year-round nectar and habitat for beneficial insects, birds, and pollinators. This steady food supply helps keep predator populations active even when vegetable crops aren’t flowering.

Well-chosen natives can also improve wind protection, shade sensitive plants, and support healthier garden ecosystems overall.

Pests & Partner Plants (Fast Reference)

Pest / Disease	Plant Allies	Dr G Shop Tip
Aphids	Nasturtium (trap), Garlic, Mint	Hang a Yellow Pest Trap at leaf height for early warning.
Cabbage Moth	Dill, Sage, Netting	Sow dill every 3 wks; back-up with Neem Meal as a soil top-dress.
Fruit Fly (Qld)	Basil*, Borage, Exclusion Bags	Mass-plant basil or use lure traps in hot spots.
Nematodes	Marigold, Mustard green-manure	Incorporate spent marigold with Neem Meal flakes for a double hit.
Powdery Mildew	Chives, Milk spray	Improve airflow & rotate crops yearly.

From Our Test Beds – Real Results

“Planting zucchinis under a nasturtium umbrella let us skip two pesticide sprays and still pull 18 kg per plant.” – Scott @ Dr G HQ

Common Slip-ups to Avoid

Token herbs – one basil won’t cut it; think clusters.
Sun vs shade clashes – pair like light needs.
No rotation – even perfect partners strip nutrients if left in the same spot yearly.

Why companion planting sometimes fails

If companion planting hasn’t worked for you before, you’re not alone.

Common issues include:

Overcrowding: too many plants, not enough airflow
Incorrect ratios: one herb often isn’t enough to make a difference
Heavy pest pressure: established infestations may need extra control methods
Weather extremes: heat, humidity, or prolonged rain can overwhelm natural systems

Companion planting is most effective as part of a broader organic gardening approach that includes healthy soil, observation, and seasonal adjustment.

FAQ

Does companion planting really work in Aussie soils?

Absolutely. CSIRO trials (2024) saw a 38 % cut in cabbage moth damage with dill borders.

Can I companion-plant in pots?

Yes – choose dwarf varieties and treat your pot like a mini guild.

How close do the plants need to be?

Within 30 cm for scent masking or shared root exudates.

Will companion planting replace fertiliser?

No, but it *does* reduce inputs. Top up with Nurture All Organic Fertiliser each season.

Does companion planting actually work in Australia?

Yes — but it works best when you think of it as one tool, not a silver bullet. In Australian conditions, companion planting is most effective when combined with healthy soil, good spacing, and regular observation. It won’t eliminate pests entirely, but it can reduce pressure and improve overall garden balance.

What vegetables shouldn’t be planted together?

Some plants compete for nutrients or attract the same pests. For example, onions and garlic can struggle near beans and peas, while brassicas (like broccoli and cabbage) don’t love growing beside strawberries. Spacing, soil health, and airflow matter just as much as the pairing itself.

How far apart should companion plants be?

Companions still need room to grow. A good rule of thumb is to space plants according to their mature size, not how they look as seedlings. Crowding plants too closely can increase disease and reduce airflow, which often causes more problems than it solves.

What are trap crops and where do they go?

Trap crops are plants grown specifically to attract pests away from your main crop. They’re usually planted near but not within the main bed, so pests gather there instead. Once pests appear, the trap crop can be removed or managed before the problem spreads.

Shop the Companion Planting Collection

Need marigold seed, exclusion bags or organic pest busters?

Browse Dr Greenthumbs – we ship Australia-wide.

About the Author

Scott Cheney is the Director and Founder of Dr Greenthumbs, with over a decade of hands-on experience in organic gardening. Growing up in rural NSW, Scott’s passion for unusual plants – from cacti to entheogens – evolved into a full-blown commitment to chemical-free gardening when he bought his first property in Wollongong. For the past 8 years running Dr Greenthumbs, Scott has developed unique, first-to-market products like TurboDirt Water Only soil and 100% dry amendment fertiliser blends. When he’s not testing new mixes, you’ll find him swapping gardening tips like your local mate, not giving the hard sell.

Tags: Pest control

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Root roids run amok

If these root roids don't give me day of the triffids I'll be ok with that so far so good

Thanks Christopher! Love the Day of the Triffids reference—here’s hoping your plants grow wild (but not *that* wild!). Glad to hear things are off to a good start. Appreciate the laugh and the feedback, mate!

Purecrop1

Purecrop1 has been my absolute go to product for IPM and organic pest and mould control for years. Use from germination through to post harvest wash and protect your investment. If you haven't used it before, try it for yourself, you won't be disappointed with its effectiveness and value for money. Quit gawking at the reviews and put it in your cart already!

Thanks legend! Love the passion—couldn’t have said it better myself. PureCrop1 really is the go-to for a reason. Appreciate you sharing your experience and giving others the nudge to get on board. Here’s to pest-free, thriving plants!

Can’t believe the difference

Have been using a high grade potting mix plants have not been happy slow growth and just not looking healthy. So I took them out of pots removed about a third of the old dirt from the bottom and anything that fell off the top and sides cleaned out the pot put turbo dirt in the bottom put a scoop of roids on the bottom and a tad more turbo dirt over it and sprinkled some transplant powder on the soil at about a third of the way up refilling with turbo dirt and then sprinkled another scope of root roids and some powder down the sides topped up with turbo dirt and a slight top dress and just before the top dress another scope of root roids and then covered with about 20 mm more turbo 2 lts of water. I could see a difference in 2 days could see a darker green coming up through the leaves in a week they where no longer sick and now 2 weeks later it’s like a different garden I can see daily grow. Can’t believe how much difference turbo dirt made thanks for your help.

Thanks Wayne! That’s an absolute ripper of a review—stoked to hear the garden’s loving the Turbo Dirt and Root Roids. Sounds like you’ve given those plants the royal treatment, mate! Appreciate you sharing your results and the play-by-play. Here’s to happy, healthy plants and plenty more green days ahead!

Outstanding gear!

Absolutely love everything Dr Greenthumbs (heck my keyboard wants always wants to autocorrect to this name)!

Thanks Timothy! Love hearing your keyboard's as hooked as you are—cheers for the awesome feedback and for backing the Dr Greenthumbs crew! Hope your plants are absolutely thriving, legend!

Wow.

Works just like the ad says, great gains.....

Thanks Paul! Great to hear you’re getting solid results with Root Roids—always good when a product does exactly what it promises. Cheers for the feedback!

Maximizing Garden Growth with Companion Planting: An Organic Approach to Pest Control