Companion planting.

Sorry if this has been covered elsewhere but in general what can and what cant be planted in close proximity.  

Hi Ruby Red, I was looking at the idea of companion planting last yeara when I first took on my allotment.  To be honest I wasn't really that organised but I did a bit of research.  Most of it is in tables but I'll try to move that across.  This should give you a start though:

COMPANION PLANTING
This is a cultural system where two or more plants are grown in close proximity in order that they may provide some form of benefit to one or all of them. This could be to deter or act as a decoy for pests and diseases, or improve growth and flavour. Usually it is the aromatic foliage or flowers of the companion plant which deters the pest or draws it away.
· The improvement in growth or flavour is probably due to the companion plant adding some of the micronutrients or the roots may support microorganisms which improve their uptake. In the case of legumes they fix nitrogen, and White Clover is included in some grass seed mixes, for this reason - it is also drought resistant so 'greens up' quicker than grass when used in lawns.
·   Some plants exude protective chemicals (allelochemicals) from their roots or foliage which can deter pests, eg. African Marigolds produce thiopene which repels nematodes so it makes a good companion plant for root crops which are attacked by nematodes. This is given the title Allelopathy.
· Tall plants can provide shelter for lower-growing ones and create a microclimate allowing them to thrive where they may not normally grow. This may also protect them from pests
· Beneficial insects can be attracted to a cropping area by planting something which they use as a food nearby, eg. adult Hover Flies feed on nectar,but their larvae feed on aphids so planting nectar-rich flowering plants will attract them.
Marigolds and Garlic have a reputation for repelling a number of insect pests such as Aphids and Carrot Root Flies. The Mexican Marigold, Tagetes minuta or Muster-John-Henry, is an annual which grows to about 1.2 m (the species name refers to the flowers not the height of the plant) The roots have an insecticidal effect on nematodes and some effect on keeled slugs. The secretions responsible begin about 3 months after sowing and also affect the growth of Ground-elder (Aegopodium podagraria), Bindweed (Convolvulus arvensis), Couch grass (Agropyron repens), Lesser Celandine (Ranunculus ficaria )and Ground Ivy (Glechoma hederacea). It is grown as a half-hardy annual which can be planted out after the risk of frost has passed, but this does not usually give them a long enough growth period to flower and set seed in Britain. Deadheading prolongs the growth for protection purposes.

· Plant French marigolds in between tomato plants to deter aphids.
· Grow carrots and leeks together. Both have strong scents that drive away each other's pests.
· Plant nasturtium with cabbages - they are a magnet for caterpillars that will then leave the cabbages alone.
· Garlic planted among roses will ward off aphids.
· Grow dill in the garden to attract aphid-eating hoverflies.
· Make sure companions plants are planted at the same time as your edible crops to prevent pests from getting a foothold.

Ole "Den" down at our lottie, grows onions between his runner beans, to ward off blackfly and always grows sweetpeas to attract bees, last year he had the best crop of the lot. Must be something init :!: As he says "Thats what me Dad always done"...

Ooops! sorry morning all    Bye PAH  ( well okay- afternoon-now )

Just be careful, as half of them will be old wives tales. :roll:

Big question, big answers, big and very important topic, little researched.

I have been very successfully growing broccoli and khol-rabi under my bean frame and cucumbers next to potatoes.

I agree with Noshed, flowers also attract lots of other beneficial insects - such as hoverflies.

    I suppose it will be trial and error. I dont want to rely on  
    chemicals because I have a good wildlife garden and dont want to
    upset the balance.

Exactly.

You raise very right questions there Wayne, I personally don't bother with inter-planting onions with carrots as it does not work in my experience, so I don't get the problem of need for completely different soil and nutritional requirements for those two crops.

Sounds like I need to experiment, I'll do some and some and see how they go this year. I had a good crop of onions last year and grown from seed too, ailsa craig. this year I have bedfordshire champion and some nice red onions from tucker seeds to try.