Why Are My Medlar Leaves Curling?

Leaf spot

Leaf spot on medlar, caused primarily by Entomosporium mespili (the same fungus that causes quince leaf blight), appears as small, reddish-brown spots on the upper leaf surface that enlarge in wet conditions. The spots may have a darker red or purple border; as they enlarge and merge, the surrounding tissue yellows and the leaf curls and drops prematurely. Medlar is generally less susceptible to leaf spot than quince, but in a wet summer and in gardens with a quince nearby (which can act as a source of inoculum), infections can become significant. Powdery mildew, Phyllosticta, and other fungi can also cause spotting and marginal browning on medlar leaves.

What to do

• Collect and destroy fallen leaves in autumn. Prune to improve air circulation through the canopy. Apply a copper-based fungicide spray in spring as buds open if leaf spot was a significant problem the previous year, and repeat every 14 days during wet periods. Avoid overhead watering. Medlar generally needs no spraying in a normal year; intervene only if defoliation becomes severe.

Fire blight

Fire blight (Erwinia amylovora) can affect medlar as it does all members of the rose family. The shoot tips collapse and turn brown suddenly in late spring, with the leaves curling and remaining attached to the dead wood; the characteristic shepherd's crook bending of the dying shoot tip is the most recognisable sign. Fire blight enters through open flowers in warm, wet spring weather. It is less commonly reported on medlar than on quince, pear, or apple in UK conditions, but should be suspected if shoot tips die back suddenly in late spring.

What to do

• Remove infected material promptly by cutting back at least 30 cm below the visible margin of browning, into healthy white wood. Sterilise cutting tools between each cut with methylated spirits or a bleach solution to prevent spread. Dispose of all infected material; do not compost it. In severe cases the entire branch may need to be removed. Do not apply high-nitrogen feeds in spring, which produce the soft growth that fire blight colonises most easily.

Aphids

Aphids, particularly the rosy apple aphid (Dysaphis plantaginea), can colonise medlar shoots in spring, causing the leaves to curl under and the shoot tips to distort. Populations are typically self-limiting once natural predators build up through May and June. Medlar is a less preferred host than apple or pear for most aphid species and infestations are usually lighter, but in some years they can be significant on the young flush.

What to do

• Pinch off heavily infested shoot tips. Apply insecticidal soap to the affected growth. Encourage natural predators by avoiding broad-spectrum insecticides and planting companion flowers nearby. A winter tar wash applied to dormant branches reduces overwintering aphid eggs. Medlar generally requires less intervention than most orchard fruit trees.

Powdery mildew

Powdery mildew on medlar causes a white, powdery coating on the young leaves and shoot tips, which curl and distort as the infection develops. Medlar powdery mildew is less common and less severe than on apple or quince, and usually requires no treatment on an established tree. It is most likely to appear in dry summers on trees in sheltered positions with poor air circulation, or on container-grown plants where roots are allowed to dry out.

What to do

• Ensure consistent watering to avoid drought stress. Remove infected shoots tips if the infection is localised. Improve air circulation. Apply a potassium bicarbonate or sulphur fungicide spray only if the infection is severe. On established garden medlars, powdery mildew rarely warrants treatment.

Frequently asked questions

Why are my medlar leaves curling?

Medlar (Mespilus germanica) leaves curl most commonly in the UK because of leaf spot diseases (particularly Entomosporium mespili), fire blight (Erwinia amylovora), or aphid infestation on the new spring growth. Medlar leaf spot causes angular, brown spots on the upper leaf surface that enlarge in wet conditions; affected leaves curl, yellow at the margins, and drop early. Fire blight causes the shoot tips to collapse and turn brown suddenly in late spring, with the leaves curling and remaining attached to the dead wood. Aphids colonise the young growth in spring, causing leaf curl and distortion. Medlar is generally one of the most problem-free orchard fruit trees, but leaf spot and fire blight are the exceptions.

Can I grow medlar in the UK?

Medlar (Mespilus germanica) grows very well in the UK and is arguably better suited to the UK climate than almost any other fruit tree. It is fully frost-hardy, tolerates a wide range of soil types including heavy clay and chalk, copes with partial shade better than most fruit trees, and is self-fertile. Medlar makes an attractive garden tree with distinctive gnarled branches, beautiful large white flowers in late spring, and rich russet-orange autumn foliage. The fruit must be bletted (softened by frost or storage) before it is edible; the flavour of bletted medlar is rich, sweet-sour, and distinctly unusual.

What does bletted medlar taste like?

Bletted medlar has a distinctive, complex flavour that is difficult to compare to anything else. When properly bletted, the firm, astringent flesh becomes soft and dark, with a rich, sweet-sour taste often described as a combination of stewed apple, wine, caramel, and spice, with an underlying earthiness. The texture is like a soft, dense paste rather than the crisp or juicy texture of conventional fruit. It is best eaten fresh or made into medlar jelly, which sets firmly and has a beautiful reddish-brown colour and an intensely fragrant flavour. Medlar jelly pairs very well with cheese and game.

When do I harvest medlar?

Medlar fruit should be harvested in late October to November in the UK, after the first frosts have touched them but before they become waterlogged by rain. The fruit is not edible at harvest; it must be bletted by storing stalk-end down in a cool, dark, frost-free place for 3 to 6 weeks. The fruit is ready to eat when it has softened from the centre outward and the flesh has turned dark and caramel-brown. You can test by pressing gently with a thumb; it should give easily. The fruit can also be left on the tree until after a frost and harvested already partly bletted, but birds and wet weather may damage it if left too long.