The list of disadvantages of hawthorn hedging are typically paired against the advantages of using the woody tree as a border hedge or landscape plant. The natural defense mechanisms of the plant make hawthorns both a blessing and bane of existence for gardeners who choose to plant them. The cockspur hawthorn (Crataegus crus-galli) is the type most often chosen as a hedge due to the large thorns and low growth patterns.
Liability - One of the natural defenses of the hawthorn are the substantial stiff thorns that cover the woody stems of some hawthorn species. Thorns as long as 2 inches are common on several species. As noted in the Ohio State University Extension tree bulletin: "Most hawthorns are armed." Hawthorn hedges could present a legal liability to the general public and pets when used on small residential properties adjacent to sidewalks, driveways or walkways.
Maintenance - The hawthorn's thorns are naturally intended to prevent damage to the plant by grazing wildlife. Those same thorns are most difficult to deal with when maintenance of the hawthorn is necessary to keep it properly shaped as a hedge. While hawthorns are deciduous the thorns are stiff and ever present. Some are curved, making them difficult to remove from clothing or skin. They are best handled from a distance exclusively with appropriate garden tools.
Flowers and Fruit - Depending on the species and location, hawthorns bloom in mid- to late spring. The dense flower display is a welcome mat for bees, which is another disadvantage if the hedge is on a small residential lot. The flowers morph into berry-like fruit that hangs densely on the plant feeding a variety of birds. Dropping fruit stains light surfaces as it decays. Depending on your circumstances the increase in avian traffic and dropping fruit can be counted as disadvantages.
Invasive Quality - In some areas of the country several species of hawthorn are considered an invasive plant. In California, invasive English hawthorn (Crateagus monogyna) has become classified as an invasive plant. Removal of invasive plants is recommended if they exist on your California landscape.
Pests - A host of pests can damage hawthorns, including aphids, spider mites, several types of scale, bark beetles, leafhoppers and sawflies. Disease known to infect the plant are leaf spot, fire blight, powdery mildew, rusts and scab. The fact that hawthorns are not known for disease- or pest-resistance is another disadvantage to using them in vast numbers necessary for a hedge.