Parsley through the cooler months
An established parsley plant can give a first-season herb corner a head start. It is a biennial, commonly grown for its leaves; it is not an unlimited source of winter pickings.
Start with a known plant
Confirm the identity and label it. Flat-leaved and curly forms are both familiar culinary parsley types; do not identify an unknown edible plant by resemblance alone.
Match care to the plant
Use a suitable container or growing position with drainage. Inspect the moisture and the plant before watering. Protection can help, but a greenhouse may still get very cold.
Pick with restraint
Harvest only healthy growth from a plant that can spare it. If little is growing, observe rather than stripping the remaining leaves. Record what actually happened.
Further detail: RHS crop guidance. This is a beginner’s plan for an unheated Cheshire greenhouse, not a report that James has grown or harvested this crop.