‘Good Companions’ by J B Priestley is not a gardening book but it might well have been as it is a tightly observed text on relationships and how one supports the other. Three main reasons for companion planting are mutual feeding, aesthetic considerations and technical or horticultural reasons. Many people will grow Marigolds or Tagetes in close proximity to Tomato plants to distract white fly.

Good Companions

• Good companions also act as living mulches suppressing weeds and  keeping the roots nice and cool.
• Form and texture combinations can work well such as spiky Phormiums with the glaucus leaves of Sedum.
• I like to vary the height with companion planting using annuals like Alyssum or ground cover under taller shrubs and trees.
• Colour combinations are a whole subject too themselves. Complementary colours or contrasting colours it is your choice but a bit of thought and some serendipity will help.

Companions for Roses.

• Garlic bulbs are said to ward off aphids and other members of the onion family such as chives, ornamental alliums are rumored to increase the perfume of roses and prevent black spot.
• The purple and blue-gray  Nepeta Catmint or the lime green Alchemilla works well with any pale pink roses and the wispy spires gracefully camouflage any blemishes that may occur on the rose’s foliage.
• Herbs and other aromatic plants make wonderful rose companions.  Lavender, scented Geraniums, Feverfew, Parsley and Thyme may suit.
• Tomatoes allegedly prevent black spot but not many people will be inclined to combine roses and tomatoes.

Bad Companions

• Not all combinations work;  Beans and Onions do not coexist very well.
• Strawberries and Tomato will not do as well with brassicassuch as  Cabbage.
• Cucumbers are tempremental when planted near Potatoes or strong herbs.
• Watch out in your garden and see what ornamental plants make Bad Companions and let us know what you discover.

Other Resources

Royal Horticultural Society RHS ‘Gardening for All’
National Council for Conservation of Plants and Gardens ‘Conservation through Cultivation.’
Garden Organic National Charity for Organic Gardening.
BBC Gardening