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Thorny problems: lilies under attack (Filed: 25/08/2001)

Helen Yemm on tough measures against rabbits and beetles, and how to cure rosemary

Beetle mania

How can I prevent lily beetles from attacking and ruining the many lilies and fritillaries on the edge of my woodland garden? Pauline Wainwright, Waverton, Chester

I AM afraid you will have quite a problem. Armies of lily beetles - stunning, scarlet-coated invaders from the warmer parts of Europe - have been marching northwards over the past few years, reducing lily colonies to shreds and driving gardeners to distraction.

Once a small platoon has arrived and found a reliable food source, it is unlikely that you will be free of them. Lily beetles overwinter in the soil and emerge in March or April to breed throughout the summer. The larvae are particularly disgusting - slimy, black and pulsating.

The best treatment is vigilance - inspect yor lilies daily, and pick off the adults and larvae by hand. Even this has its pitfalls, as the beetles have a sneaky habit of dropping to the ground and playing dead if they sense danger.

While they are lying on their backs with their bright red carapaces hidden, they are hard to spot. All those you find, you must squash underfoot. (Sorry, but you can't be lily-livered if you are a lily-lover.)

Obviously, it helps if you are able to grow all your lilies and fritillaries in one area, so that you can keep an eye on them.

Life will also be simpler if you grow the lilies in pots, because you can then use the best chemical weapon against them - Provado Ultimate Bug Killer aerosol, which contains imidacloprid. This is a systemic insecticide and is suitable only for plants in containers.

But, forewarned is forearmed. Look out for the blighters earlier next year, before they go on the rampage.

Herbal treatments

Since the spring, one of my two four-year-old rosemaries has been dying, branch by branch - while, of course, its neighbour has been going from strength to strength. My soil is rich loam over a clay subsoil, to which I added broken bricks and stones to improve drainage when I planted them. What is wrong? T Jones, Cambridge

I presume you are wondering if there is some mysterious rosemary disease or pest that is causing this most annoying state of affairs. Rosemary is slightly susceptible to the fungal disease phytophthora.

A rosemary beetle has also recently arrived on the scene, but it is ladybird-sized and therefore is unlikely to have escaped your inspection.

Those apart, the main difficulty with rosemary is its sensitivity to winter waterlogging. Clearly, you are aware of this, yet it is still the most probable cause of your problem.

However much we hate to do it, there comes a time when plants become so hideous that chucking them out is the only sensible course of action. Bite the bullet and dig up your rosemary. Try harder to loosen up your clay subsoil, to improve the drainage in a wider area, and start again with a new plant.

If the two rosemaries were different varieties, take a cutting from the one that is thriving and which may be more tolerant of your soil conditions. But if your new plant starts to suffer - and who knows how much wet we are going to have to get used to - perhaps you should give up and plant something else.

Bashful 'Beauclerk'

I have two philadelphus [mockorange]. 'Belle Etoile' flowers well against a south-facing wall in full sun. 'Beauclerk' puts out long shoots but has no flowers; it is in a partially shaded position under a horse chestnut tree, facing west. Have you any advice? Brad Wilson, Bourne End, Bucks

Hello again. You must be the same hapless Brad Wilson who wrote to me a few months back about a dying pair of Garrya elliptica bushes.

Of your two shrubs, P. 'Belle Etoile' would always be the one that gives you the better run for your money. It is more sweetly scented and a nicer-looking bush altogether. It sounds to me as if P. 'Beauclerk' is behaving badly in an attempt to tell you something.

Competition for light, water and root-space under the canopy of a horse chestnut must be fierce, and I suspect this is why it is producing such long, non-flowering shoots. Check that these new shoots are not infested with damaging aphids in the sheltered environment of an overhanging tree.

You could move 'Beauclerk' to a better site in autumn, which might do the trick, and/or feed it with rose fertiliser in spring to encourage flowering.

Also, do remember that shrubs that flower in early summer do so on young wood produced the previous year, so don't be tempted, in the interests of "tidiness", to snip off all those long shoots that appear each summer. They will carry next year's flowers.

Bunny habits

Are there any flowers suitable for cutting that I can grow and which rabbits do not eat? Fiona Wheatley, by email

I spoke to Sarah Raven, author of The Cutting Garden, about this problem - but she was no more optimistic than I am. She has found that rabbits eat almost anything, especially in the spring, when they show a particular partiality for her wallflowers.

She went so far as to say that there are no annuals that will survive the attention of a hungry bunny, though they seem to leave her biennial white foxgloves alone.

However, if you are serious about growing flowers for cutting, it might be a good idea to cultivate them in a small enclosure, with a 3ft-high fence of wire.

The chicken wire will have to be firmly pegged down for each foot of its length, and will probably need to be renovated each year. (Proper, permanent rabbit-proof fences should be partially buried to deter the dastardly diggers.)

A further advantage of the fence is that it will support all those lovely floppy-stemmed flowers that would otherwise succumb to the combined force of wind and rain long before they made it as far as a vase.

Write to Thorny Problems at helenyemm1@aol.com or The Daily Telegraph Gardening, 1 Canada Square, London E14 5DT. Helen can only answer queries through this column.

-- Anonymous, August 25, 2001