Bleeding Milkcap (Lactarius rubrilacteus)

🏷️ Description

If you ever find yourself wandering the conifer forests of western North America between summer and early winter, keep an eye out for a mushroom that bleeds — not blood, but a rich purplish-red latex! Meet Lactarius rubrilacteus, also called the Bleeding Milkcap. Though edible, it’s more of a curiosity than a delicacy, but its distinctive appearance and reactions make it a favorite among foragers and mycophiles alike. Let’s dive in! 🍂

🔎 Identification

🍄 Cap: Convex when young, becoming centrally depressed or shallowly vase-shaped with age. It measures (5 to 14 cm) 2 to 5.5 inches across, often showing concentric zones of orangish, brownish-orange, and tan. Moist caps are sticky and tend to develop dirty green stains as they age or bruise.

🍃 Gills: Decurrent (running down the stem), close to crowded, narrow, starting dull orange and deepening with age. They bleed a dark red to purplish latex when cut or damaged, which stains green on exposure.

🍂 Stem: Colored like the cap, measuring (2 to 6 cm) 0.79 to 2.36 inches tall and (1 to 2.5 cm) 0.39 to 0.98 inches thick. Solid and brittle when young, becoming hollow with age. It bruises green where handled and may have a whitish bloom at the base.

🥩 Flesh: Whitish and fairly firm, staining pink to purplish when sliced. The taste is slightly acrid or mild, with a faintly aromatic but not distinctive odor.

💧 Latex: Sparse and striking — a dark red to purplish-red "milk" that remains dark on exposure. This is a key identification trait!

🧪 Spore Print: Pale yellow to beige.

🔬 Microscopic Features: Spores are ellipsoid, measuring (7 to 10 × 5.5 to 7.5 µm), with amyloid warts and partial reticulation. The pileipellis forms an ixocutis, and hymenial macrocystidia reach up to 70 µm long.

🌲 Habitat & Ecology

A mycorrhizal species, Lactarius rubrilacteus forms symbiotic relationships with Douglas-fir (Pseudotsuga menziesii) and various pine species (Pinus spp.). It grows scattered to gregariously on forest floors, often hidden beneath conifer duff. You can find it in:

• Summer to fall in the Rocky Mountains

• Fall to winter along the West Coast

• Distributed throughout western North America

It prefers younger stands of Douglas-fir and pine, but it can be found in a range of coniferous habitats.

🧪 Chemical Reactions

A mushroom for the chemistry-curious:

• Potassium hydroxide (KOH): Cap turns dull brown, losing its bluish tones.

• Melzer’s reagent: Minimal visible reaction.

• Sulfovanillin: Most of the mushroom stains reddish-brown, though old roots remain unchanged.

🍽️ Edibility

While edible, this mushroom isn’t particularly sought-after. Its grainy texture and scanty latex don’t make for memorable table fare, though it's occasionally enjoyed in parts of the Pacific Northwest. The dark, wine-red latex and its unusual appearance make it more of a mycological prize than a culinary one.

👀 Look-Alikes

Lactarius rubrilacteus belongs to the Clade Deliciosi, a group known for their orange hues and latex-producing abilities. It’s often confused with:

• Lactarius deliciosus: Milk is bright carrot-orange, cap zonation more distinct.

• Lactarius sanguifluus: European species under pine with reddish milk.

• Lactarius paradoxus and L. subpurpureus: Related North American species with overlapping traits.

What sets L. rubrilacteus apart is its reddish milk (never orange), distinctive green staining, and a habitat preference for Douglas-fir and pines west of the Rockies.

Photo sources:

Photo 1 - Author: Arvel Hernande (CC BY 4.0)

Photo 2 - Author: Sharon Squazzo (CC BY 4.0)

Photo 3 - Author: Monica Ventrice (CC BY 4.0)

Photo 4 - Author: Reagan peschke (CC BY 4.0)