Plant of the Month: August 2025

Title image above is copyright © Kristi Ellinopoullos

First published 1st August 2025

Family: Geraniaceae (includes Geranium and Pelargonium)
Genus: Geranium (includes the cranesbills (the true geraniums))

Botanical/Binomial Name: Geranium robertianum
Meaning of Name:
Geranium, from Ancient Greek γέρανος (géranos, ‘crane’): seed capsule resembling a crane’s beak; and
robertianum, from Latin Robertianum (‘of or pertaining to Robert’): Robert’s herb (possibly Saint Robert, a French monk who reputedly used this plant to cure people with illnesses)

Common Names: Herb Robert, Robert’s Geranium, St. Robert’s Wort

Botanical Characteristics: Herbaceous | Annual or Biennial | Self-Pollinating | Frost hardy
Propagation: Sow seed | Self-seeds readily

Plant Description:
Herb Robert is a true geranium which grows to about 300-400 mm high. It is a famed medicinal herb with internal and external healing properties.

The plant has a delicate appearance and produces dainty 15 mm diameter mauve flowers in spring through to autumn.

Growing Information:
Herb Robert is moderately frost-tolerant, prefers moist soil, and can grow in semi-shade to full sun in temperate climates. (It will do better in part-shade in very hot climates.) Leaves and stems may turn red in full, bright, sun.

This plant is propagated by seed, and self-seeds readily. However, the timing of seed collection is crucial, as the seed capsules have an ‘explosive’ nature and will propel the seed some distance away and in all directions. To collect by hand, either pick the seed pods when they are about 2 cm long and feel plump and hard between two fingers, or simply cover the pods with a breathable bag to trap the expelled seeds when the capsule opens. If picking the capsules, allow to dry for 3-4 days minimum. Sow seed in a shady spot to 5 mm depth for best germination, which can take up to six weeks. Keep moist with regular watering.

Alternatively, take advantage of the ‘explosivity’ by keeping a flowering plant in a pot and placing this where you would like more to grow. Repeat by moving the plant to another location as other capsules mature and show signs of opening.