Morchella populiphila is the newest addition to the group of North American half-free morels. This strictly Northwestern North American species is characterized by a fruiting body that grows up to 15 centimeters tall, a rigid and pitted conical cap that attaches approximately half way down the stem, and a strong association with black cottonwood trees (Populus trichocarpa).[i]
M. populiphila was first described as a unique species in 2012 as a result of molecular DNA studies by the mycologist Kerry O’Donnell which showed that this species possessed distinct characteristics that warranted its recognition as a separate species. Before 2012, M. populiphila was thought to be the same species as Morchella semilibera. However, O’Donnell’s molecular analysis showed that M. semilibera was a separate and strictly European species of Morel, while M. populiphila was a strictly North American species of Morel occurring in northwestern states. Unfortunately in the North American continent there are at least two other species of fungi also referred to as “half-free” morels both of which cannot be separated from M. populiphila by observation of their physical features, with or without a microscope.[ii]
The epithet “populiphila” reflects the fungus’s affinity with the black cottonwood trees of northwestern North America and its reliance on them for its life cycle.
Identification and Description[iii], [iv]
Cap: The cap of this species is conical, hollow, and attaches to the stem in a skirt-like manner, approximately halfway down the stem. It typically measures between 2 to 5 centimeters in both length and width at its widest point. The cap structure is formed by the intersection of 10-20 primary vertical ridges and a fewer number of secondary shorter vertical ridges with several transecting horizontal ridges. The ridges themselves are approximately 1 mm wide, flat with sharp, smooth, edges, and are yellowish brown to honey brown color when specimens are young. In age, ridges become rounded or eroded and darken to a brown to black color. At the center of these ridges are vertically arranged, smooth pits that are whitish to pale brown when young, becoming yellowish or grayish brown at maturity.
Stem: The stem is typically 2.5–11 centimeters tall and 1–5 cm wide. The width of the stem is roughly equal throughout, but may be tapered towards the top in some specimens and may be inflated near the base in warm, wet conditions. In younger specimens, the attachment of the cap halfway down the stem often conceals it, but as the mushroom matures, the cap undergoes significant growth, becoming more visible. Mature specimens also develop shallow longitudinal furrows and become hollow. The stem typically has a white to watery brownish hue, and is covered in mealy whitish granules giving the stem a cow tongue-like texture.
Spores: The spores of Morchella populiphila measure 20-25 by 12-18 micrometers. They are smooth, elliptical with homogeneous contents. The spores are hyaline in potassium hydroxide (KOH).
Spore print: This half-free morel has a bright yellowish orange spore print.
Flavor and Edibility: Morchella populiphila is an edible species. Although, when compared to its other half-free morel cousins, it is not as highly valued due to its fragile nature and its milder flavor.
Habitat: Morchella populiphila is believed to exhibit both saprobic and mycorrhizal associations during different phases of its life cycle. It is commonly observed growing in various patterns, either solitary, scattered, or gregariously. Notably, this species tends to thrive in dried-out riverbeds, particularly in the presence of black cottonwood trees (Populus trichocarpa).
Range: Based on current research, Morchella populiphila is confirmed as a species exclusively found in Northwestern North America, specifically within the states situated Northwest of the Rocky Mountains. Its distribution range is believed to stretch from Oregon to Nevada, encompassing Northern California. While there are occasional references to M. populiphila in Europe, these instances can be attributed to either confusion with the indistinguishable strictly European species, M. semilibera, or the presence of “ true” M. populiphila specimens in Europe, likely introduced through North American tree species. Therefore, it is important to recognize that the native range of Morchella populiphila remains limited to Northwestern North America, with any occurrences outside of this region requiring careful scrutiny and clarification.
Fruiting Season: As one of the early risers among morel mushrooms, this species emerges during the spring, heralding the arrival of the season. The typical fruiting season of Morchella populiphila lasts from March to May.
Look-A-likes
The identification and differentiation of Morchella populiphila from similar-looking mushrooms can be both straightforward and challenging. Thanks to its distinct morphological features, distinguishing it from unrelated mushroom species, such as Verpa bohemica, is relatively straightforward. However, differentiating M. populiphila from closely related “half-free” morel species becomes exceedingly difficult. These species cannot be discerned from M. populiphila based solely on their physical characteristics, whether observed with the naked eye or under a microscope. This complexity underscores the challenge in distinguishing between these closely related species and underscores the critical role of molecular analysis in accurately identifying and classifying Morchella populiphila.
As mentioned, distinguishing between half-free morel species from North America and Europe based on macro or micromorphological characteristics alone is not feasible. Instead, accurate identification relies on their specific habitats and geographic distributions. Here are some key details for differentiating between the species:
- Morchella populiphila: This species thrives in Northwestern North America and is closely associated with black cottonwood trees (Populus trichocarpa) in its habitat. Identifying its presence within this region, particularly in dried-out riverbeds, can indicate the likelihood of encountering Morchella populiphila.
- Morchella punctipes: Found in hardwood forests of Northeastern North America, Morchella punctipes has a distinct geographic distribution. Its occurrence in these regions, combined with its association with hardwood trees, can help differentiate it from other half-free morel species.
- Morchella semilibera: This strictly European species is absent in North America. Its presence is limited to European habitats, making it a distinguishing factor for identification purposes.
Lastly, a similar appearing non-related species that may be confused for M. populiphila is Verpa bohemica. However, there is a distinctive characteristic that sets them apart: the cap of Verpa bohemica hangs completely freely from its stem, in contrast to that of M. populiphila which attaches half way down the stem.
Toxicity, Safety & Side Effects
Misidentification is the only worry when it comes to Morchella populiphila. They don’t look entirely similar but be aware of False Morels which can be poisonous and sometimes mistaken for all different kinds of Morels.
References:
[i] Kuo, M. (2012, October). Morchella populiphila.
[ii] Kuo, Michael, et al. “Taxonomic revision of true morels (Morchella) in Canada and the United States.” Mycologia, vol. 104, no. 5, 2012, pp. 1159–1177,
[iii] Kuo, M. (2012, October). Morchella populiphila.
[iv] D. Arora (1986) Morchella semilibera In “Mushrooms Demystified: A Comprehensive Guide to the Fleshy Fungi,” Ten Speed Press, Berkeley (pp. 791–3)
