Scarlet firethorn

Identification and origin

Pyracantha coccinea belongs to the rose family, Rosaceae. Its native range runs from central and southern Europe to Iran: Spain, France, Switzerland, Italy, the Balkans, Greece, Bulgaria, Turkey, Crimea, the Caucasus, Lebanon, and Syria. It has naturalized elsewhere, notably in North America.

It is an evergreen to semi-evergreen shrub with a stiff, upright habit that turns open and leggy without pruning. It grows fast, sometimes more than 2 ft a year, and commonly reaches 8–13 ft tall and as wide. The reddish-brown stems carry many spines shorter than 1 in. The alternate, narrowly elliptic leaves, 1–2 in long, are glossy dark green, paler underneath, with finely scalloped edges; in hard cold they bronze and partly drop.

From late spring into early summer, small five-petaled white flowers with a somewhat unpleasant smell open in clusters on the previous year’s stems and draw pollinators. In fall, tight clusters of small orange-red fruits about 0 in across ripen and hang on into winter if the birds leave them. Its spines keep deer away.

It is used as a barrier hedge, on slopes, or trained against a wall, away from areas where children and pets play.

Common cultivars: ‘Lalandei’, vigorous and very widely grown, with abundant fruit but prone to scab; ‘Kasan’, compact; ‘Chadwickii’, hardy and spreading; ‘Lowboy’, spreading, 2–3 ft tall, prone to scab. ‘Mohave’, ‘Teton’ (golden yellow fruit), ‘Apache’, ‘Navaho’, and ‘Fiery Cascade’ resist fire blight and scab.

Light

Full sun, at least six hours a day, gives the most flowers and fruit. It accepts partial shade, but a shady spot, such as against a north-facing wall, clearly reduces berrying. This is an outdoor shrub; only dwarf cultivars suit container growing.

Watering

For the first two years, water whenever the soil at the base of the shrub feels dry to your finger. Once established, it handles heat and drought and seldom needs watering. Keep an eye on wall-trained plants: the foot of a wall stays dry even after rain. Drought while the fruit is forming makes it drop before coloring, so in dry spells water deeply until the berries take on their color. Water the soil, never the foliage, because overhead sprinkling encourages scab.

Potting mix

It grows in almost any moderately fertile soil, whether chalky, clay, loam, or sand, acidic or alkaline, as long as it does not stay waterlogged. Overly rich soil produces rampant growth that is more prone to fire blight, and fewer berries. Regular feeding is unnecessary; above all, avoid nitrogen.

Temperature

Hardy, it grows in USDA zones 6 to 9, and in zone 5 with the hardiest cultivars. It withstands winters in the range of 5 °F to -4 °F and tolerates heat well. In cold regions, shelter it from icy winds, which burn the foliage.

Repotting

Scarlet firethorn resents transplanting: buy a container-grown plant and leave it where you put it. Plant when the ground is not frozen, ideally from fall to spring; dwarf cultivars in pots can go in during any season. Space specimen plants 5–10 ft apart and hedge plants 20 in apart. Against a wall, plant at least 20 in out from its base to avoid the dry zone, then mulch at least 2 in deep.

Pruning

Flowers and fruit form on wood at least one year old, so keep as much two-year-old growth as you can. Wear thick gloves, because the spines can cause allergic reactions.

On a freestanding shrub, remove only unwanted, damaged, or diseased branches, in late winter or spring; on a mature plant, taking out about a fifth of the older wood after flowering renews it. Avoid pruning in late summer or early fall: you would remove next year’s flowers, and the regrowth could suffer cold damage.

On a wall-trained plant, shorten outward-growing shoots in spring, then in late summer cut side shoots back to just above the berry clusters; tie in new shoots while they are still flexible. A hedge is trimmed two or three times between spring and the end of summer, sparing as many berries as possible. At the end of winter, knock off old, rotted fruit with a broom.

Propagation

Seed works for the species. Seeds germinate only after three months of cold stratification; then sow them in spring. Cultivars usually do not come true from seed.

To get an exact copy of a cultivar, especially a resistant selection, take semi-ripe or hardwood cuttings. Never use diseased material: planting or propagating infected stems brings fire blight into the garden.

Common problems

• Shoots that suddenly blacken during bloom, tips bent into a shepherd’s crook, dead flowers that stay attached: fire blight (Erwinia amylovora), favored by warm (70–81 °F), humid weather. Prune in dry weather while the plant is dormant, at least 4–6 in below the affected area, disinfecting the tool between cuts; remove badly affected plants.
• Velvety olive-green to black spots, fruit blackened as if covered in soot, leaf and berry drop: scab (Spilocaea pyracanthae). Remove affected shoots, avoid overhead watering, and choose resistant cultivars.
• Branches dying back, small sunken cankers: Botryosphaeria canker; cut well below the canker.
• Discolored, sticky, or mined leaves: aphids, scale, spider mites, lace bugs, leaf miners.
• Few berries: heavy pruning, a cold, wet spring that hampers pollination, late frost, drought, shade.

The same symptom can have several causes: look at the whole plant, the soil, and the exposure before acting.

Toxicity

Scarlet firethorn is considered potentially harmful: its ornamental fruit should not be eaten by people or pets. The berries contain traces of a cyanide-like compound. Still, no serious poisoning has been reported in people: a few berries are considered harmless, a large amount can cause mild nausea or vomiting, and for small children the main risk is choking. Dogs that ate large amounts of berries showed no signs of poisoning. The real hazard is the spines: a puncture turns red, swells, and itches, and a spine lodged in a joint or an infected wound needs medical attention.