How to identify Geranium robertianum (Herb Robert)
This project collects observations of Geranium robertianum (Herb Robert) in California for the purpose of facilitating identification and preventing misidentification of this species in iNaturalist.
Photo tips:
- It’s important to get a picture of the entire plant.
- It's also helpful to get close-up pictures of the face of the flowers, sepals, leaves, and fruits, if present.
- If there are multiple plants in the picture, it’s helpful to crop your photo to focus on the plant of interest.
How to identify Geranium robertianum:
- Height: An erect, many-stemmed plant that grows up to 50 cm (20 in) in height.
- Stems: multiple (often red) stems.
- Leaves: dark green leaves, pinnately lobed or dissected with 5 segments that are ~90% divided to base or midrib. Sparse hairs. Leaves turn red at the end of the flowering season.
- Flowers: flowers are small with 5 petals in shades of pink to red-purple or sometimes white or blue. Petals are broad, unnotched, and clearly separated with white or occasionally darker pink stripes. The center of the flower is white. Anthers are normally dark purple, but they can also be orange. Sepals have very long hairs of different lengths.
- Fruit: 1–3 collar-like rings and long fibers at the tip.
- Habitat: Found in grasslands and woodlands in the San Francisco Bay area and central coast ranges of California.
- Flowering time: March through May.
Similar species:
- Geranium purpureum (Little-Robin)
- Geranium dissectum (Cut-leaved Crane’s-Bill)
- Geranium yeoi (Greater Herb-Robert)
- Geranium lucidum (Shining Crane’s-Bill)
See: https://www.inaturalist.org/observations/94162488
How to differentiate G. robertianum from G. purpureum :
- G. robertianum flowers are about 3x the size of G. purpureum (10–14 mm vs 5–9.5 mm).
- G. robertianum has a white center and more prominent white/pink streaks on its petals; G. purpureum does not have a white center and its streaks are more subtle.
- G. robertianum anthers are purple; G. purpureum anthers are yellow. Tip: the pollen of both species is yellow, so when comparing the anther color, pick a flower that has anthers which have not opened.
- G. robertianum has sepal and petal hairs that are much longer than those of G. purpureum.
- The leaves of G. robertianum and G. purpureum and are very similar. Stems are often red in both species. It is usually regarded as impossible to differentiate these two species using vegetative features alone.
- Reference: https://cambridgewildflowers.blogspot.com/2020/05/herb-robert-geranium-robertianum-and.html
How to differentiate G. robertianum from G. yeoi:
- G. robertianum flowers are about 1/3 the size of G. yeoi.
- G. robertianum flowers have a white center; G. yeoi flowers don’t.
- G. robertianum has hairier leaves than G. yeoi.
References:
- Calflora: https://www.calflora.org/app/taxon?crn=3806
- Jepson eFlora: https://ucjeps.berkeley.edu/eflora/eflora_display.php?tid=77514
- Monterey Wildflowers: https://montereywildflowers.com/geraniaceae-geranium/
- Cambridge Wildflowers: https://cambridgewildflowers.blogspot.com/2020/05/herb-robert-geranium-robertianum-and.html
iNaturalist:
** https://www.inaturalist.org/taxa/55925-Geranium-robertianum#Description
** https://www.inaturalist.org/projects/geranium-robertianum-herb-robert
** https://www.inaturalist.org/projects/geraniums-cranesbills-california
** How to identify Geranium robertianum (Herb Robert)
