Collinsonia canadensis (Horsebalm, Rich Weed, Stone Root)

USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. 3 vols. Charles Scribner’s Sons, New York. Vol. 3: 153.

Where Commonly Found: Meadows, fields,CT, MA, ME, NH, NY, RI, VT.
How to Identify:
(For unfamiliar words: Wikipedia Glossary of Botanical Terms).
Go Botany Key for Collinsonia canadensis Click on more images.
Missouri Botanical Garden’s description of Collinsonia canadensis
Flower Type:  Cream to light yellow spike-like racemes or a panicle pyramids occur at the end of the central stem and are up to 8″ long by 6″ across with a central stalk and several side branches becoming progressively shorter up the stalk.  Individual flowers are 1/3″-1/2″ long with short-tubular to bell-shaped, green calyx with 5 teeth, 10 narrow longitudinal dark green ridges, 2 long fertile stamen and a slender style on the ovary.  The trumpet-shaped corolla is narrow at the base with 5 spreading lobes at its mouth, 2 upper and 2 side that are oval or oval-deltate shapded and 1 lower lobe that is the largest and violin shaped.
Flower Time:  August to September.
Leaf Arrangement:  Opposite leaves along the entire length of the stems.  The central stem is light green, hairless to moderately pubescent, rarely branched, with 4 bluntly angled shallow channels.
Leaf Type:  Ovate leaves, 2″ – 6″ long by 1.5″ – 4″ across with coarsely serrate-crenate margin, an acute tip and wedge-shaped to rounds leaf base.  The upper surface is medium to dark green, hairless to sparsely short pubescent.  The lower surface is light gray-green, hairless to sparsely short pubescent and glandular-punctate (giving the appearance of glistening dots when in sunlight.)  The petiole is light green, hairless to moderately short-pubescent.
Height: 2′-4′
Seed Collection:  Mature fruit contain 4 nutlets that hang from the calyx.

Attracts: Bees (especially bumblebees), Moths, Birds
Use:  Naturalizing
Light:  Part Shade
Hardiness Zone:  4 – 8  USDA Zone Map
Soils:   Moist
Notes:  Collinsonia canadensis, Horse Balm, is a great filler plant with glossy leaves, for part shade naturalized gardens, producing clusters of tubular yellow flowers attractive to many pollinators.  Both the leaves and flowers have a citronella or lemon scent.  Noted as deer-resistant by UVM.
Native to:   RARE IN VT, EXTINCT IN NH, native to the rest of the Northeast (except ME), SE and Mid-Atlantic US:  Biota of North America Program (BONAP) – North American Plant Atlas (NAPA).


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