Vive la résistance

Advances in breeding mean many plant varieties withstand pests and diseases better than ever

Once upon a time, a gardener had to be a defence line – armed and ready with a battery of pesticides in a never-ending war against slugs, bugs and disease. But not any more.

Thanks to advances in breeding, plants these days should pretty much defend themselves.

This suits the low-maintenance gardener, who doesn’t have the time for attacking aphids and the like, as well as the organically minded. To cater for both, plant breeders have been focusing on creating pest- and disease-resistant versions of popular plants.

Roses: these plants were once thought of as high-maintenance, but most of the varieties introduced in the past 10 years are less trouble. “In the early 1990s, we realised there wouldn’t be a future for the rose unless it could resist disease,” says Gareth Fryer of Fryer’s rose nursery in Cheshire. “People were so sick of black spot, they weren’t buying roses, so all the breeders had to make health their priority.”

The hard work has paid off. There is now a large selection of disease-resistant varieties on the market. Fryer’s itself is the creator of ‘Lucky’. Rose of the Year 2009 and the result of 15 years’ work, it is a floribunda with pink petals in a traditional shape and has exceptional disease resistance.

Other new varieties include ‘Sweet Haze’, a tiny pink shrub rose; ‘Lancashire’, a scarlet ground-cover rose; ‘Gardeners’ Glory’, a golden climber; and ‘Strawberry Hill’, a romantic variety that smells deliciously of myrrh. All are winners of the new Gold Standard, an accolade awarded by breeders for good plant health, as well as flower power and scent.

Old roses that have stood the test of time are another option. Albas and gallicas are rarely ill, but they won’t repeat flower as modern roses do. The best is ‘Félicité Parmentier’ (1836), a gorgeous alba that flowers for six weeks.

Fruit trees: the other main area of horticulture that has been transformed by disease-resistance breeding is fruit – especially apple trees, which are often attacked by scab, a fungus that leaves scars and cracks on the fruit.

“Eighty per cent of UK apple-tree spraying is for the prevention of scab,” says Hamid Habibi of Keepers, a fruit-tree nursery in Kent. “So, apple growing has been transformed by the introduction of scab-resistant trees.” New varieties include ‘Rajka’, red apples with a faintly strawberry flavour; ‘Scrumptious’, which produces honey-sweet apples; and ‘Herefordshire Russet’, the fruit of which tastes as good as a ‘Cox’.

“People plant a ‘Cox’ or a ‘Gala’ without realising how much spraying is done to grow supermarket versions,” says Habibi. “The equivalent grown at home is always poor. With one of the new varieties, you won’t have to spray and you’ll enjoy their apples.”

The same applies to many other fruit favourites, such as the ‘Victoria’ plum, which is susceptible to disease, especially silver leaf. Habibi recommends growing ‘Opal’, a smaller plum that tastes and looks similar.

Hostas: hosta leaves are caviar to slugs. However, the slimy pests are less partial to those with a thick leaf. Leathery varieties such as the ghostly, blue-tinged ‘Halcyon’, and ‘Sum and Substance’, which has huge gold-green leaves, are largely unaffected once established (though the young leaves can be eaten). The same is true of upright hostas, such as ‘Krossa Regal’, the leaves of which don’t touch the ground and so thwart slugs. Richard Ford, of Park Green Nurseries in Suffolk, suggests growing hostas in the open. “People plant them in damp, dark places, which is where slugs congregate; try planting in semi-shade instead.” Slug-proof alternatives for the shady corner include lady’s mantle, ferns, solomon’s seal and foxgloves.

Trees and hedging: since it was discovered in the UK 15 years ago, the fungal disease box blight has grown to become one of the main problems reported to the Royal Horticultural Society. Beatrice Henricot, principal plant pathologist at RHS Garden Wisley, Surrey, suggests the following alternatives for evergreen hedge planting and trimming: Ilex crenata (box-leaved holly);Berberis buxifolia(a dwarf berberis with box-like leaves and yellow flowers in summer); and Teucrium xlucidrys (hedge germander), which has a great aroma.

The latest disease creating havoc in British gardens, according to Henricot, is a fungus called Pseudocercospora cladosporioides, which affects olives. The leaves develop spots, then yellow and eventually fall off. Opt for the silvery-leaved ornamental pear ‘Pendula’ instead of an olive.

Take care when deciding on hedging, as yew, viburnum and privet can be plagued by the UK’s most common disease, honey fungus.Safer evergreen bets are pyracantha and cotoneaster. If you want to be a little more daring and don’t mind a deciduous hedge, try Amelanchier lamarckii, which has bronze leaves and white flowers in spring.

Source: The Times

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