Companion planting is explained in the Organic Gardener's Handbook by Margaret Elphinstone and Julia Langley (Thorson's, pounds 9.99) as the art of using one plant to ward off the pests and diseases of another. You may plant garlic at the base of a peach tree to keep away leaf curl or, as Mr Smith explained in his original letter, use a concoction of chilli to keep aphids off the roses.
However, readers, who have been voluble recently on the subject of pergolas (Independent, 22 July), frangipani (Independent, 12 August) and the meaning of nespole (see Cuttings, below) have been oddly silent on the subject of companion planting. What can this mean?
Isabel Pierce wrote from Dover to say: "Some years ago I noticed that a miniature rose I'd planted was badly infested with greenfly, alongside it a garlic towering above ..." This was not exactly what I wanted to hear, though it mirrored my own sad experiences.
Doreen Gotch, of London NW4, generously sent me a copy of a perfect period piece called Companion Plants, written by Helen Philbrick and Richard Gregg in 1966. Companion planting was then part of the theory of biodynamics which was based on the "effects exerted on plants and animals by their earthly and cosmic environment".
It is an enchanting book, full of the dreamy hocus-pocus that I remember with great nostalgia from the Sixties. But does it help keep cabbage white butterflies from my cabbages? Sadly, no. And am I going to try and cure my peach leaf curl by spraying with a mixture of horsetail tea, stinging nettle tea and pigeon droppings, as suggested in the Philbrick/Gregg manual? Again, no. I am more convinced by research that suggests you should keep peach trees covered against rain in early spring to prevent leaf curl spores taking hold.
Blackfly have run amok on the double nasturtiums 'Hermine Grasshof' that I was so proud of. There are ladybirds about on the plants but they do not seem to be doing anything. "Perhaps they're waiting for the blackfly to fatten up," suggested our youngest daughter ghoulishly, after waiting in vain for some violence to enliven the tedium of shelling peas.
The artemisia, which was similarly attacked by blackfly, thickly clustered on the growing shoots, has been cleaned up. Hoverflies might be the heroes here, for there have been vast swarms of them in the garden, more welcome than the swarms of flying ants, one lot of which came zooming into the kitchen and blacked out the window more efficiently than a wartime curtain.
The hoverflies like the lilies planted in pots by the front door: 'Citronella', which has been there for the past seven years, and 'Yellow Blaze', which I thought last year I would try as a change. I rather regret it. 'Citronella' has very graceful heads, the flowers held at right-angles to the stem, the yellow petals reflexed and freckled with black. 'Yellow Blaze' has flowers which face the sky and, to my mind, this is not an improvement. They look stodgy.
Both kinds have excellent ginger-coloured anthers on long stamens, but whereas with 'Citronella' you see these in profile, like lizards' tongues looping out to pick up flies, in an upright flowering lily such as 'Yellow Blaze' the stamens are more circumspect, standing upright in a tight little bunch.
I am evidently in a minority over this business of upright-flowering lilies, for Parkers' new catalogue is full of them: 'Sterling Star' is an ivory upright, 'Corina' is a dark red upright and 'Stargazer' is red with a white border. 'Yellow Star', on the other hand, a sideways-facing tiger-lily type flowering in August and September, looks excellent, just what I need in the round border which is rather quiet in August.
The International Flowerbulb Centre carried out some interesting trials of lilies at the Northern Horticultural Society's garden at Harlow Carr. It grew lilies in pots of two different composts, one lot coir-based, the other a mixture of perlite, peat and John Innes No 3. The foliage of lilies grown in the coir compost was much lusher and darker than that of lilies in the other mix, even though both lots got the same weekly feed of Fisons Flowerite.
In terms of number of flowers, the lilies grown in the mix did slightly better than the ones grown in coir compost. In terms of impact, the most highly rated were 'Connecticut King' (deep yellow flowers in June and July), 'Enchantment' (nasturtium-orange flowers spotted with black), 'Yellow Submarine' (not listed in The Plant Finder) and 'Mont Blanc' (creamy white flowers in June and July). 'Cote d'Azur' it noted, a deep pink lily often recommended for pots and tubs, tended to fade quickly once it had opened which substantially reduced its impact.
A newcomer, Gladiolus papilio, to which I have been making daily pilgrimages in the garden, has a slightly snooty, what-am-I-doing-among-this-mob air about it. It is flowering now on a thin wiry stem about three feet high with hooded flowers of cream overlaid with dirty purple. The stamens are bright blue and on the two lower petals are spoon-shaped blotches of pale acid yellow, frilled round with purple.
It is a riveting plant and I am making the most of it this summer, because it has the distinct aura of something that is not going to flower for me again. "I'm sorry you are having to slum it," I said to it one morning, "but there it is. We all have to make sacrifices. These are hard times."
Graham Stuart Thomas's book on Perennial Garden Plants tells me that it comes from Natal and was introduced in 1872. "A forlorn, sad-looking charmer," he says, adding that it was probably the main influence in producing the modern mauve-tinted hybrids. This species, though, seems a million miles away from your average Dame Edna Everage gladdy.
The heat has been having a curious effect on some flowers. The second crop of 'Nevada', a modern shrub rose which is supposed to have large single whiteish-cream flowers, has turned out to be rather deeper pink than 'New Dawn'. Its main crop is in late May and June, but it usually provides a taste of something later on. It has never before changed character quite so markedly between its first crop and its second. 'Nevada' is thought to be a hybrid from the deep pink species R. moyesii. I wonder if, when under stress, it tends to drift back in character towards its parent?
Everything growing in the vicinity of the huge beech tree (like 'Nevada') is under stress this summer. You may leave the sprinkler on for two hours but, within a day, the plants are flagging again. The tree must be siphoning up water faster than an elephant at play. Poor thing. On a journey over to north Devon last week, we passed masses of beeches, brown and brittle from head to foot. It was a very sad sight. Trees newly planted this spring will be similarly at the end of their tethers. If you water nothing else, save them. Give them at least 10 gallons at a time.
My plantings of biennial and perennial flowers - foxgloves, forget-me- nots, catananche, shaggy shasta daisies, alpine asters - made in a laboriously prepared seed bed, have been demolished by a mole who zoomed in there after I had been watering. Perhaps the watering attracted worms. He looped about in the bed, raising a sequence of shallow runs more complicated than Spaghetti Junction and lifting the seedlings on his back as he did so. By the time I found them they were fried to a crisp.
Wildlife gardens - who needs them?