Troubleshooting
Cupani sweet pea problems — and how to fix them
Cupani sweet pea (Lathyrus odoratus 'Cupani') is generally forgiving once you match its basics, but a few issues come up again and again. Here is what each one looks like, why it happens, and the fix.
Aphids (blackfly / greenfly)
Black bean aphid (Aphis fabae) commonly colonises growing tips and leaf axils, especially in spring. Pinch out heavily infested tips; spray with insecticidal soap. Encourage ladybirds and lacewings by avoiding broad-spectrum insecticides.
Powdery mildew in heat
Cupani is an old-fashioned type and slightly more heat-sensitive than some modern varieties. Mildew appears as temperatures climb. Keep roots cool and moist; space plants 20–25 cm apart for airflow; apply sulphur fungicide preventatively in warm spells.
Short flowering season in hot summers
Bicolour scented types like Cupani fade and stop flowering quickly once daytime temperatures consistently exceed 23°C. For the longest season, make a second sowing in late winter for succession, and position plants where they receive afternoon shade in the hottest months.
Prevent cupani sweet pea problems before they start
Most cupani sweet pea issues are care-mismatch, not bad luck. Dial in the basics:
Cupani sweet pea problems — FAQ
Why is my cupani sweet pea aphids (blackfly / greenfly)?
Black bean aphid (Aphis fabae) commonly colonises growing tips and leaf axils, especially in spring. Pinch out heavily infested tips; spray with insecticidal soap. Encourage ladybirds and lacewings by avoiding broad-spectrum insecticides.
Why is my cupani sweet pea powdery mildew in heat?
Cupani is an old-fashioned type and slightly more heat-sensitive than some modern varieties. Mildew appears as temperatures climb. Keep roots cool and moist; space plants 20–25 cm apart for airflow; apply sulphur fungicide preventatively in warm spells.
Why is my cupani sweet pea short flowering season in hot summers?
Bicolour scented types like Cupani fade and stop flowering quickly once daytime temperatures consistently exceed 23°C. For the longest season, make a second sowing in late winter for succession, and position plants where they receive afternoon shade in the hottest months.