Beauty and the beasts: Lilies herald the second half of summer – but only if the dastardly lily beetle doesn't get to them first

Anna Pavord takes on a tiny but mighty foe

(Rex Features)

I've become deeply attached to my lilies. Unfortunately, so have the lily beetles. How does it work, this insectan grapevine? How do the wretches know that here, on land that previously housed chickens and brambles, there is now a succulent crop of martagons and regales and long- necked longiflorums?

The beetles moved in early and I've been fighting them all summer. So have gardeners in most of the rest of the country. A terrifying map published recently showed how far they have spread from Surrey where they were first found around 25 years ago. Scotland is still free of them. It will be interesting to see how long that lasts. Will the spread north continue? Or will the beetles be deterred by the tougher winters in those parts?

Earlier on, while our lilies were still developing, I sprayed some of them with an insecticide called Provado Ultimate Bug Killer. The creatures shown on the bright yellow bottle include lily beetle, as well as aphids, thrips and sawfly. "Safe for use on all flowers," it says on the label, but you need to take notice of the small print, which warns you that foliage may be affected. I found the damage so disfiguring I stopped using the spray. Many leaves were scorched and the buds at the top of the stems were imprisoned by the damaged leaflets bent over them. I peeled the dead stuff away after a while, but the buds were already distorted.

It was a measure of my increasing passion for lilies that I reached for a bottle in the first place. I can't remember when I last used either insecticide or fungicide. I'm a relaxed kind of gardener and in the main believe that friend and foe will stagger towards some kind of equilibrium in the garden. The problem with the lily beetle is that it doesn't have foes. Except me. So after giving up on the spray, I became super-vigilant. I patrolled the lilies almost every day, catching the red devils (they move more slowly than most beetles) and jumping on them. Hard.

I didn't ever suppose I'd eliminated them, but by early July, I certainly felt they were under control. Until, that is, I started finding the lily beetle's filthy grubs stuck to the undersides of the lily leaves, wrapped in a coating of their own excrement. They are hideous things and though stationary, more unpleasant to deal with. When you go out after the beetles themselves, you are keyed up by a sharp, slightly scary instinct for the hunt. The grubs invite nothing but disgust.

The beetles emerge around March and after having their way with your fritillaries, move on to the new stems of lilies. Egg laying starts later and each beetle can produce 200-300 of the things. The grubs hatch in 10 days and eat for a month. If you don't catch them, they drop to the soil and overwinter, cocooned, in the soil. Then the whole ghastly cycle starts again the following spring.

There seems no decided opinion as to whether some kinds of lily are more prone than others to attack. Some say martagons and regales are the beetle's favourites. In our garden, that's not so. The regales, set in a big group on their own on a bank, have not been touched. The martagons, growing at the opposite end of the garden in a semi-shaded area, have also been left alone. The worst hit have been the lilies growing in the hottest places – the ones planted in pots along the south-facing wall of the hut where I work, and groups that I put among grasses in a sunny well-drained area, to peak in July and August.

I suppose the lily thing started because I'm constantly aware of the fact that the garden in the second half of the summer is never as effective as it is in the first. There's bulk in plenty – tree peonies, big euphorbias, fennel, thalictrum, spiky leaves of Iris orientalis, tall, thin spires of Irish yew – but the scene needs a jolt, a wave of something to do what the tulips do during April and May. Lilies, flowering mostly in July and August, seemed the ideal solution.

Tulips are so cheap that you can afford to think of them almost as annuals. Lilies are not, but if you settle them in well, they'll come back year after year. In pots, they are fantastic, but if the pot is pushed up close to a wall, the growing stems tend to lean outwards and may need staking. White, sweet-smelling 'Casa Blanca' has been in the same pot on our terrace for seven years and still creates wonderfully sturdy stems, packed with outrageously ruffled, come-hither blooms, nearly 20cm (8in) across. It's richly scented – an important attribute for lilies set close to where you sit in the evenings.

Any good lily catalogue (such as the one produced by HW Hyde and Son) should tell you whether the lily you have in mind needs alkaline or acid soil. That's the first thing to consider. In a pot, of course, you can cheat by using ericaceous compost. But acid or alkaline, the soil needs to be well drained. Again, in a pot, you can arrange that quite easily. I use crocks at the bottom and then fill the pot halfway with our own compost. It doesn't matter if it's a bit rough – it will help the pot to drain quickly. Five bulbs will fit comfortably into a pot 45cm across. Fill up the pot, depending on the lilies you've chosen, either with ericaceous compost or with a loam compost mixed 2:1 with 6mm grit. Terracotta pots will keep the compost cooler than trendy galvanised ones. Once lilies start to grow, they need regular feeding and watering. I use Osmacote slow-release granules, sprinkled on the surface of the compost.

If you plant in autumn, the pots are best kept under cover for winter so the compost does not get too wet, though it must not dry out either. If you plant in spring, the bulbs, which unlike daffodils have no protective coat, will have been hanging around out of the ground for some time. So there are disadvantages in both seasons. HW Hyde, where I buy our lilies, delivers in March, so, relieved of the responsibility of deciding when to plant, I can concentrate on what.

I like tallish lilies with reflexed flowers: tiger lilies (L. lancifolium), L. henryi, L. leichtlinii, 'Citronella' – all at the orange-yellow-red end of the spectrum. I love the way that, in this type of lily, the stamens loop forward from the back-turned petals, juggling their bundles of pollen. All bear their darkly spotted flowers on stems at least 120cm (4ft) tall. They look terrific between the grassy stems of deschampsia or spearing through the lax branches of Euphorbia mellifera, just recovering now from the beating it got this last winter.

As these three are already well established in the garden, I'm ordering some new types of martagon lily. They, too, have spotted, reflexed flowers – a dull kind of raspberry pink in the standard version – and fit well into informal, wildish parts of the garden, flowering in June. I bought clumps of the ordinary ones from our old garden, where we found them fighting through hefty spreads of nettle. Given this provenance, it seems mad to say they are slow to establish, but it's true. Not difficult, but slow, because they don't like being moved. I've finally got the lovely white form of L. martagon settled, so have put in for some of the soft, creamy apricot forms that have recently been introduced – 'Mrs RO Backhouse', 'Slate's Select' and 'Guinea Gold'. They are £4.75 each, so three of each will blow the whole of my lily budget. Never mind. It's money well spent.

HW Hyde and Son, The Nursery, New Road, Ruscombe, near Reading, Berks RG10 9LN, 0118 934 0011, hwhyde.co.uk