Plant guide

Scarlet pimpernel.

Lysimachia arvensis

Pronounced ly-si-MA-ki-a ar-VEN-sis

Also known as Common Scarlet Pimpernel, Poor Man's Weather Glass, Scarlet Pimpernel, Shepherd's Calendar, Shepherd's Weather-Glass

The scarlet pimpernel is a charming, low growing plant often found in fields and gardens. It is well known for its small, star shaped flowers that close up when the sky turns cloudy. It is a hardy little plant that spreads easily in the right conditions.

At a glance

Care level: Easy
Plant type: Annual herb
Light: Full sun to partial shade
Indoor light: Bright indirect
Water: Every 3 to 7 days
Mature size: 12 to 20 inches
Growth rate: Fast

Care

Keep the soil consistently moist but not soggy to help this plant thrive. Watch for yellowing leaves, which often signal that the soil is staying too wet for too long. It prefers a spot with plenty of light to keep its stems from getting leggy.

Watering: Water when the top inch of soil feels dry to the touch.
Feeding: Apply a balanced liquid fertilizer once a month during the active growing season.
Pruning: Trim back leggy stems to encourage a bushier growth habit.
Repotting: Repot only if the plant becomes root bound or if you need to refresh the soil.
Soil: Well draining, fertile soil
Soil pH: 6.0 to 7.5

Safety

Pets: This plant can be toxic to cats and dogs if ingested.

How to identify it

Small star shaped orange or red flowers
Opposite, oval shaped green leaves
Square stems typical of primrose family
Flowers close during cloudy weather

Science

Family: Primulaceae
Genus: Lysimachia
Order: Ericales
Class: Magnoliopsida

Taxonomy resolved against GBIF.

Also in

Plants toxic to cats and dogs

Is your scarlet pimpernel looking unwell?

This page is a general guide. Pocket Botanist diagnoses problems from a photo of your actual plant, works out watering for your light and conditions, and reminds you when care is due.

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This guide was generated with AI and checked against GBIF taxonomy. It is general information, not horticultural or veterinary advice. Read about how we build these guides.