Fertilizing
Feed from spring until early autumn, either with liquid fertilizer every 1–2 weeks or with solid organic fertilizer once a month. A balanced fertilizer with plenty of phosphorus and potassium supports flowering and berries.
- Stop feeding during winter dormancy and resume when new growth starts in spring.
- Pause for about 4 weeks after repotting.
Placement
Keep the tree outdoors all year in full sun; in very hot summers, light afternoon shade prevents leaf scorch. It is hardy in the ground, but roots in a shallow pot are not, so protect the pot once frosts drop below about -5°C (23°F).
- In winter, use a sheltered spot, a cold frame or an unheated shed with some light.
- Give it good air circulation but shelter from strong, drying winds.
- Do not keep it indoors: it needs the cold winter rest.
Pruning
Cotoneasters respond very well to pruning. Remove dead, weak or crossing branches in late winter or early spring, before new growth starts. During the growing season, let shoots grow 6–8 leaves, then cut them back to 2–3 leaves.
Flowers form on short spurs on older wood. Trim new shoots after flowering rather than in spring if you want flowers and berries.
Wire young branches, which bend easily, any time outside hard frost. Old branches become stiff and brittle, so shape them with guy wires and check often for wire marks as branches thicken.
Repotting
Repot young trees every 2 years and mature trees every 3–4 years, in early spring just before the buds open. The tree tolerates root pruning well, so you can remove up to a third of the root mass.
- Use a free-draining mix such as akadama, pumice and lava rock.
- Cotoneaster is not fussy about pH and grows in slightly acidic to alkaline soil.
Watering
Water thoroughly as soon as the top of the soil feels dry, which in summer can mean daily. The tree survives short dry spells but grows best with evenly moist, never waterlogged soil.
- In winter, water much less but do not let the root ball dry out completely.
- Ordinary tap water is fine.
Seasonal care
- Spring: Repot every 2–4 years just before bud break and start feeding when new growth appears. Enjoy the white or pinkish flowers.
- Summer: Water daily in hot weather and keep the tree in full sun with some afternoon shade in heat waves. Trim new shoots back to 2–3 leaves after flowering.
- Autumn: Red berries ripen and deciduous species color red before dropping their leaves. Stop feeding once growth ends.
- Winter: Keep it dormant outdoors and protect the pot from frosts below about -5°C (23°F). Do structural pruning in late winter.
Common problems
Cotoneaster is tough, but like other members of the rose family it has a few typical pests and diseases.
- Fire blight: Shoot tips and flowers suddenly turn black-brown as if scorched, with a hooked tip. Cut out affected branches well into healthy wood, disinfect your tools after every cut and burn or bin the clippings.
- Aphids and woolly aphids: Curled young leaves or white, woolly colonies on the bark. Rinse them off with water and treat heavy infestations with insecticidal soap.
- Spider mites and scale: Speckled, dull leaves with fine webbing, or brown bumps on twigs. Mist the foliage in dry heat and treat with horticultural oil.
- Root rot: Yellowing leaves and dieback in soil that stays wet. Use a free-draining mix and let the surface dry slightly between waterings.