The Veg Lab – Does Companion Planting actually work?

New for 2025 is The Veg Lab which debunks some of the most commonly asked questions when growing vegetables. I’ll be experimenting these claims in my own vegetable garden to see whether they are true or false.

‘There are no Gardening mistakes, only experiments’

Janet Kilburn Phillips.

Experiment – Does Companion Planting actually work?

First up is Companion Planting. There’s lots of information about planting certain flowers or herbs with certain vegetables to keep the pests at bay and bring the beneficial insects into your vegetable garden.

But does any of it really work? I’ve decided to test this with a scientific veg garden project.

Hypothesis

I’m testing to show whether Companion Planting works or not.

I have planted summer cabbage plants into the middle of a raised bed with Shallots, Garlic, Rosemary and Calendula plants. These are widely reported to repel pests, specifically the cabbage white butterfly.

No Netting on Brassicas

There will be no netting protecting the cabbage plants, they will be completely open to pests, especially the dreaded Cabbage White Butterfly.

Any vegetable grower with any experience of caterpillars eating all their cabbages will now ask – Am I mad? no netting, there will be no cabbage left!

I love an experiment to see if I get proven wrong, it’s human nature to be curious about processes and it helps us understand and learn to adapt to alternative growing methods.

Experiment Timings

Month Experiment takes place: Early May to Late July.

Cabbage White Butterfly Hatches: April.

Outcome

Good Outcome = Companion Planting works and I have full size cabbages with no caterpillars.

Bad Outcome = The butterflies have ignored the garlic, onion & rosemary smells that are supposed to repel them and laid their eggs on the cabbages. Cabbages have been eaten by caterpillars.

Experiment contains:

  • 1 x Wooden Raised Bed – 2.4m x 1m.
  • Elephant Garlic,
  • Garlic,
  • Shallots,
  • Rosemary,
  • 3 x Summer cabbage plants,
  • 3 x Cauliflower
  • Calendula plants (at the end of the raised bed),
  • 3 x Giant Alliums.
Cabbages amongst garlic & shallots

Experiment Diary

April

  • Shallots, Garlic, Elephant Garlic, Rosemary have been in the ground for a number or months already settling in.
  • Calendula Seeds sown directly into the front of the raised bed.
  • Summer Cabbages & Cauliflowers planted in amongst the rosemary, garlic and shallots.

May

  • A couple of cabbage white butterflies spotted in the garden but no where near the cabbages. 👍
  • Cabbages and Cauliflowers are settling in and getting larger.
  • Garlic, shallots and elephant garlic are larger as well.
  • Calendula are flowering!

June

  • Baby cauliflowers and cabbages are forming!
  • I have noticed there is a distinct lack of cabbage white butterflies this year than in previous years.
Raised Bed – Companion Planting Experiment – June 2025

Conclusion

Yes! Companion Planting Works

I am very impressed and surprised by this experiment and I will definitely be growing vegetables more closely with garlic and onions. They definitely seem to be working in the repelling butterflies.

However it is worth noting, there were less cabbage white butterflies in Year 2025, than in recent years in May & June.

Sowing Cauliflower and Summer Cabbages early (in January) is definitely worthwhile.

The companion planting in between garlic and shallots has worked well, the cabbage white butterflies that did fly past, were not interested in the cabbages, instead they liked the Loganberry fruit flowers running along the fence.

Distractions are the key in smell (onions and garlic) and white flowers.

The Veg Lab Series

For a FREE download on Top Tips on Companion Planting & a Veg Garden project every month – Join The Grow Veg Club here.



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