Some plants just love being together. Gillian Vine finds out about some symbiotic relationships in the garden.
About a month ago, I described some plants that help others fight off bugs and diseases.
I mentioned marigolds (Tagetes) which produce a substance toxic to nematodes, tiny eelworms that attack the roots of many plants, such as potatoes, and I've just sown three varieties of marigold - overkill, I suppose - to grow in my husband's Maris Anchor patch.
If nothing else, it will add a decorative touch.
An interest in natural remedies started last summer when I tried an old way of keeping flies out of the kitchen, growing basil in a pot above the sink.
Any flies that got into the house ignored the kitchen, so I will definitely be repeating the basil trick.
Ants are not usually a problem in the South, but where they are, mint is supposed to repel them, something I wish I had known when I lived in Auckland, where anything with sugar in it had to be kept in sealed containers.
I hadn't lived there long when a visitor asked for sugar for her tea, so I handed her the covered sugar bowl.
She lifted the lid and found a mass of ants - but no sugar, even though I had filled the bowl only a few hours earlier.
Another use for mint is putting twigs of it between rows of cabbages to keep white butterflies away, but I'd rather use the alternative herb, sage, for fear the mint would sprout and take over the garden.
Allelopathy is the beneficial or harmful effects of planting two plants close together.
For example, spinach likes being close to strawberries but does not grow as well alongside cabbages.
Tomatoes and asparagus are good companions, while celery or bulbous-rooted celeriac go well with any member of the onion family.
I have never grown sunflowers near potatoes, so cannot vouch for the claim that the two close together cause a poor potato crop, nor for the claim that potatoes do not like pumpkins.
Some of the benefits of companion planting may be because it means moving away from mono-cropping (having a big area planted in a single crop) but many simple remedies - such as marigolds or nasturtiums to keep away whitefly - are now being endorsed by scientific research.
But even if scientists say it's true, I can't see me growing garlic alongside my roses to improve the perfume.
The good old ways
When the first Europeans went to North America, they found Native Americans growing sweetcorn and pumpkins together, a pairing now recognised as mutually beneficial.
An early-20th-century photograph of a Maori garden at Jerusalem, on the Whanganui River shows tobacco growing alongside gourds.
As tobacco accumulates potassium, which encourages strong root growth and is important in the development of fruit (in this case pumpkins), the Jerusalem pairing makes sense.
