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Carrots with Onions - Companion Plants

Carrots with Onions - Companion Plants

The carrot and onion team is truly symbiotic 

With the amount of work that goes into preparing a vegetable patch prior to planting and subsequently all the way up until harvest, there's nothing worse than seeing an entire crop laid to waste by any pest or disease. 

Some plants produce scents or chemicals to protect themselves from such undesirables and can be useful if placed next (or near) to plants that can't defend themselves in the same way. 

The scourge of any carrot crop is the carrot root fly (Chamaepsila rosae). Attracted by the smell of the carrots, a scent which is strongest when the leaves are cut during thinning out, root fly can be confused if another smell is present to mask that of the carrots.

Enter, the onion. The pungent odour given off by members of the onion family (including leeks and chives) will mask that of the carrots, keeping them fly free. 

In return, the carrots actively repel onion fly (Delia antiqua) in much the same way. 

Here are just a few tactics to get the most from your carrot and onion team:

  • Ensure soil composition is optimal for the pair; carrots shouldn't be planted into freshly manured ground, though onions require nutrient rich soil. Consider using a legume crop in autumn for a happy compromise.
  • Carrots and onions prefer ground with good drainage, but should not be allowed to dry out.
  • Both carrots and onions enjoy sunny spots offering at least 8 hours of sunlight per day.

Planting carrots in a raised bed will further reduce the risk of carrot fly infestation since the flies travel close to ground level. 

You can also plant onions around the edges of your garden as a vegetable fortification, since they will deter other pests too!

Image: Andris Tkacenko/Shutterstock

Something incorrect here? Suggest an update below:
Chris L
Home Produce Grower

It isn't really the height of your planter that will keep carrot fly away Josie. Carrot fly lays it's eggs in seedlings and the larvae feeds on the growing roots. They are easy to side step.

Which state are you located? I am guessing you won't be planting until at least August so when you plant, make sure you use heaps of good compost, plant spring onion among your seedlings and if you can, society garlic around your garden edge and you will be fine. Carrots also need well drained, moist soil and sun for 8 hours a day. Monday, 29 June 2015

Josie S

Could anyone help me with this - How high do my veggie boxes/planters have to be to keep the carrot fly away? Monday, 15 June 2015