VAL BOURNE suggests tips to stop box hedges becoming diseased

Gardeners love their box hedges and topiary. But in recent times it's driven some of them to tears because they have had to remove the whole lot due to a disfiguring fungal disease called box blight (Cylindrocladium buxicola). It strips the leaves away to leave dead twiggy growth.

I first noticed bare box bushes over 20 years ago in several large gardens which were heavily visited. At first it was dismissed as an ageing process. But when the new box was replanted it also succumbed.

It's thought that the disease was introduced from Central America because it's endemic in Mexico and the Caribbean. However, frost doesn't touch this fungal disease despite its exotic, warm heartland. It was first reported in the UK in the mid-1990s and by 1998 it was widespread.

However, it was around long before it was officially recognised. Under favourable conditions the disease spreads quickly and clogs the plant's arteries, slowing down the sap until the box eventually dies. Water droplets carried on the wind spread the sticky spores and when the box is cut in early June the shears or clippers also spread it along. Clothing will also transfer spores. Washing the shears with detergent will help.

The disease starts with spots on the leaves and these develop into larger brown areas. The fungus also causes black streaks on the stems and branches and patches of greyish fungus appear on the lower leaf surface. But most gardeners only notice it once the leaves begin to disappear.

There are other box' substitutes and they include the floppier wall germander (Teucrium chamaedrys), the small-leaved Japanese holly (Ilex crenata) and Phillyrea. You cannot replant box if you are affected because spores linger in the soil, so you have to find an alternative.

It's worth remembering that fungal diseases tend to thrive in damp, muggy conditions and most box sold in garden centres has been raised under cover where airflow is restricted. The best solution is to propagate your own from cuttings from healthy box. Late summer is the ideal time to do it and I noticed the technique pictured when I visited Bridewell Organic Garden and Vineyard, near Witney . Their next open day is on July 13 from 2pm until 5pm. Call 01993 864530.

They use two pots. The larger one has a layer of gritty compost and the box cuttings are placed round the edge. The smaller pot sits on top and keeps the cuttings damp and in place. The beauty of this technique is you can lift the top pot to see if the cuttings have rooted. Look for 5in long, semi-ripe cuttings from this year's growth. Trim below the leaf joint and remove some lower leaves before plunging into compost.

This week is the recognised time to trim box, traditionally always cut on Derby Day when whole households were at the races. Trim it any earlier and frost can brown the regrowth. My box chickens are certainly due for a haircut!