Crataegus (Hawthorn) – What Is Wrong With My Tree?

Hawthorn: A Flowering Ornamental Tree

Hawthorn, belonging to the genus Crataegus, encompasses a group of deciduous shrubs and trees prized for their deep green foliage, clusters of creamy white or pink, scented flowers in spring, and bright, berry-like fruits called haws that often persist into winter.

Native across temperate regions of the Northern Hemisphere, hawthorns are versatile, thriving in various soil types, though they prefer well-drained conditions and full sun to partial shade.

Their dense, thorny nature makes them excellent choices for privacy hedges or windbreaks, while their ornamental attributes, including spectacular fall foliage, add aesthetic value. The haws are a boon for wildlife, attracting birds and small mammals.

In addition to their ecological benefits, hawthorns are steeped in folklore and have been used in traditional medicine, particularly the berries, for heart-related conditions.

Cratategus laevigata ‘Paul Scarlet’

Despite their hardiness, hawthorns are susceptible to certain pests and diseases, so proper care is essential.

Hawthorn: Leave Symptoms

Hawthorn leaves can exhibit various symptoms, including browning, curling, and spots. These issues often result from pests, diseases, or environmental stressors.

Dots, blotches or spots on leaves

• Cedar-hawthorn rust: Can cause yellow to orange spots on the leaves, premature leaf drop, and the presence of white, tubular structures (fungal spores) on the underside of the leaves.
• Powdery mildew: It manifests as white or grayish powdery spots, primarily on the upper surfaces of leaves and stems.
• Leaf blight or Entomosporium Leaf Spot: A fungal disease that manifests as small, reddish-brown spots with yellow halos on leaves. Spots darken and enlarge as the leaves mature, causing premature leaf drop.
• Pear sawfly: The feeding pattern of the larvae results in transparent patches on the leaves, which eventually turn brown once the tissue dies.
• Leafminers: Visible signs include serpentine-like tunnels or blotches on leaves, discoloration, and, in heavy infestations, premature leaf drop
• Lace bug: Tiny spots of white to yellowish-brown appear on the upper surface, resembling pinpricks.

Portions of leaves are absent or damaged

• Fall webworm: Consumes entire leaf sections, sparing major veins, and can strip trees of leaves in severe infestations.
• Japanese beetle: Skeletonizes leaves by consuming tissue between veins, resulting in a lace-like appearance.
• Tent caterpillar: Larvae consume complete leaf sections, occasionally sparing major veins, leading to severe defoliation in high population instances.
• Gypsy moth: The gypsy moth caterpillars can cause extensive damage by feeding on the leaves, leading to defoliation and weakening of the plant
• Pear sawfly: Pear sawfly larvae feed voraciously on the foliage, creating a skeletonized appearance, as they typically leave the veins and a thin layer of tissue intact.

Leaves wilted and discolored

• Fire blight: Leaves wilt and turn a dark brown or black, often remaining on the tree; the disease gives them a scorched appearance.
• Drought stress: Insufficient water, high temperatures, and dry soil conditions. Leaves exhibit wilting, browning at edges, and may become crispy to the touch, sometimes followed by premature leaf drop.
• Leaf spot diseases: Lead to discolored, yellow, brown, or black spots on leaves, which may lead to wilting if the infection is severe.
• Spider mites: They can cause leaf discoloration in hawthorn trees. These tiny arachnids suck the sap from the leaves, leading to stippling, yellowing, or bronzing of the foliage as they disrupt the plant’s normal physiological processes. Severe infestations can lead to significant leaf drop and overall tree stress.
• Root rot: Wilted leaves that may yellow, even with moist soil, often followed by leaf drop; the plant’s vigor decreases overall.

Hawthorn: Trunk and Branch Symptoms

Hawthorn trunk or branch issues can manifest as holes, cracks, discolored areas, dead twigs and branches, often indicative of fungal diseases or pest infestations.

Holes in branches or trunk

• Roundheaded appletree borer: It creates noticeable holes in hawthorn branches or trunks, indicating larval burrowing. These invaders compromise tree health, often causing weakening, dieback, and increased vulnerability to other issues.
• Sapsucker: This bird drills tiny holes into the bark of trees and consumes the sap that seeps out.

Discolored or cracked bark

• Fire blight: New shoots bend into a distinctive shepherd’s crook shape. Branch cankers have dark, sunken and cracked bark, sapwood is streaked reddish brown.
• Roundheaded appletree borer: The bark on the lower parts of the stems shows signs of cracking or splitting. Certain patches of the bark darken, accompanied by sap exuding from entry points.
• Sunscald: Intense sunlight, particularly in winter, heating the bark, leading to cell damage. This can be followed by discolored, often sunken patches on the sunny side; bark may crack or peel away.
• Frost crack: Sudden cold snaps causing differential contraction between bark and wood. This can lead to long, deep, vertical cracks usually on the trunk’s colder side; may reopen annually.
• Canker (Bacterial canker or Phytophthora canker): sunken, necrotic lesions on stems, branches, or trunks that disrupt nutrient flow, potentially weakening or killing the plant.

Dead branches and twigs

• Quince rust: It can lead to dead branches and twigs, as the fungal pathogen disrupts nutrient flow, causing dieback and severe weakness in the tree’s structure.
• Fire blight: Sudden wilting and blackening of branches; curled tips resembling a shepherd’s crook.
• Roundheaded appletree borer: There are noticeable dead branches and instances of them breaking off.
• Drought stress: Brittle, lifeless branches and twigs; leaves may drop prematurely or appear scorched.
• Winter injury: Twigs and branches die back; bark may split; discolored, wilted, or dropped leaves.

Hawthorn: Fruit and Flower Symptoms

Fruit deformed or with unusual growths

• Quince rust: Fruit and stems might exhibit swelling or unusual shapes, with potential yellow to orange spots on leaves. Fruits develop protruding white tubular structures that bear fungal spores, creating a spiky look; these turn orange upon spore release. A vivid orange, powdery substance representing spores can be observed on the vicinity of affected leaves and fruit.
• Cedar-Apple Rust: Fungal infection from nearby junipers. Fruit with yellow spots, progressing to large, brown, deformed areas; orange gelatinous horns during wet spring.
• Cedar-hawthorn rust: In severe cases, the fungus doesn’t just affect the foliage but also spreads to the fruit and young, green stems, causing deformities.
• Apple Scab: Fungus (Venturia inaequalis) during wet, cool weather. Olive-black spots on fruit surface; severely infected fruits become distorted and may crack.

Discolored flowers

• Fire blight: Flowers appear water-soaked, then turn dark brown to black, resembling fire damage; often affects blossoms in clusters.
• Botrytis Blight: Fungus (Botrytis cinerea) thriving in cool, wet conditions. Grayish-brown fuzzy mold on flowers, petals becoming discolored, brown, and shriveled; rapid spread under humid conditions.
• Frost Damage: Flowers show browning or blackening, wilted petals; damage typically appears after unexpected late frost events.