Why resistant choices pay off

A tree is the longest-lived purchase most of us ever make in a garden. A crab apple planted this winter could still be standing in fifty years, so it is worth a little research before you dig. Diseases such as canker, honey fungus and powdery mildew are already present in many British gardens, and once they are established, chemicals are rarely the answer — in a domestic setting there are barely any approved for use anyway. Choosing species and cultivars with genuine resistance means less spraying, less pruning of dead wood, and fewer evenings spent fretting over a sickly tree.

The three problems worth planning around

Most tree trouble in the UK comes down to a handful of familiar adversaries.

• Canker. Fungal canker attacks apples and pears, while bacterial canker troubles cherries, plums and other stone fruit. Both enter through pruning cuts, weather damage and leaf scars, flourishing in wet, mild weather. Look for sunken, cracked patches of bark and dieback on the shoots.
• Honey fungus. This soil-borne killer spreads underground through black bootlace-like strands, rotting roots and leaving white sheets of fungus beneath the bark. There is no cure. Once it is in your soil, it stays, and susceptible trees die one by one.
• Mildew. Powdery mildew dusts leaves with a floury white coating that disfigures foliage and weakens growth. It thrives on dry roots, humid air and poor circulation — the classic conditions of a crowded, enclosed suburban garden.

Reliable, disease-resistant trees for British gardens

Start with these if honey fungus is a known problem, or if your soil is heavy and damp.

• Yew (Taxus baccata). The gold standard for honey fungus resistance. Slow, dense, endlessly clippable and superb for birds, which nest in it and eat the fleshy red arils.
• Hawthorn (Crataegus monogyna and C. laevigata). Also resistant, tolerant of clay, and one of the best native trees for wildlife — blossom for bees, haws for winter thrushes, dense thorns for nesting.
• Field maple (Acer campestre). Good resistance, small enough for most gardens, with buttery autumn colour and corky winged seeds.
• Hornbeam (Carpinus betulus). A better bet than beech on wet, heavy soils, and happy either in a hedge or as a stand-alone tree.
• Holly (Ilex aquifolium). Resistant and usefully shade-tolerant. Plant both male and female forms if you want the winter berries.
• Crab apple 'Evereste' (Malus). Widely grown for its scab and mildew resistance, with white blossom, small orange-red fruits and reliable autumn colour.
• Rowan (Sorbus aucuparia). Compact, tolerant and generous with berries. Choose named forms with colourful fruit for extra interest.

Do bear in mind that resistance is not immunity. Ash, once a staple of British gardens, is now a poor investment because of ash dieback, and birch, lilac and privet are all vulnerable where honey fungus is active.

Fruit trees, roses and other mildew-prone favourites

Fruit trees are where cultivar choice really matters.

• Apples. Older cultivars such as 'Ashmead's Kernel', 'Egremont Russet' and 'Worcester Pearmain' are generally regarded as far less canker-prone than 'Cox's Orange Pippin', which sulks in wet western gardens.
• Pears. 'Conference' is the most dependable choice for a cool, damp site; save 'Doyenné du Comice' for a warm, sunny wall.
• Plums and cherries. Bacterial canker is the enemy here, so always prune in summer rather than winter, and choose reliable sorts such as 'Victoria' and 'Morello'.
• Roses. Skip fussy Hybrid Teas in favour of species and rugosa hybrids — Rosa rugosa, 'Geranium' and 'Roseraie de l'Haÿ' all shrug off mildew and blackspot, and produce hips for the birds.

Planting and aftercare that keeps resistance working

Good genes only go so far; a stressed tree will fall ill whatever its label says. Plant bare-root between November and March, when the soil is workable and not frozen. Improve the ground with well-rotted manure or garden compost, plant at the same depth the tree grew in the nursery, and keep the graft union clear of the soil on fruit trees. Mulch 5–7 cm deep, keeping it well away from the trunk, and water thoroughly for the first two summers rather than little and often. Thin congested branches so air moves freely through the canopy, clean your secateurs between trees, and go easy on nitrogen feed — soft, sappy growth is exactly what mildew and aphids adore.

Resistance and wildlife go hand in hand

Happily, the toughest trees are often the best for wildlife. Hawthorn, rowan, field maple, crab apple, holly and hazel all feed pollinators in spring, caterpillars in summer and birds in autumn and winter, and they do it without a single spray. Leave fallen leaves where you safely can, resist the urge to tidy every corner, and let a little ivy climb. A garden full of healthy, resistant trees is not just easier to look after — it is a livelier one, too.