Beware the manroot!
In this Spring season, more than in seasons past, I’ve been seeing an incredible lot of wild cucumber flowering along my favorite Bay Area trails. The wild cucumber, Latin name Marah macrocarpus, is a member of the Cucurbitaceae, or gourd family. It is quite a pretty vine when it flowers, and does bear resemblance to most garden-variety cucumber plants. But that’s where the similarity ends.
A wild cucumber flowers along the Zinfandel Trail in the hills of Cupertino, California
For while you would eat a garden-grown cucumber, the last thing you’ll want to do – should you ever find yourself foraging for food in the wilderness – is chow down on the fruit of the wild cucumber, also known as bigroot, manroot, and old-man-in-the-ground.
How is such a pretty vine accorded such an unflattering name? While I must admit to not having dug one up personally, apparently the taproot of the wild cucumber is large, fleshy, alternately woody, and can weigh up to one hundred pounds. But if that doesn’t intrigue you very much, the main thing you should know about the manroot regards the fruit that it bears: the seeds of the manroot are extremely poisonous.
The soft spines of the fruit of the manroot. I discovered this cuke along the Sunol-Ohlone Trail on the return leg of an early-April hike to Murietta Falls.
Like many of Nature’s local denizens, the wild cucumber is a plant worthy of admiration. But mostly, it deserves the healthy respect that comes from knowledge gained. I probably don’t have to tell you that it’s better to take a picture than to take a swallow!
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September 3rd, 2009 17:24
This isn’t Marah macrocarpus which is confined to SoCal – it’s actually two different species. The top picture is Marah oreganus and the lower picture is Marah fabaceus.
September 7th, 2009 14:15
Always willing to learn more from the experts, I followed up on Kipp’s comment and learned that he is the webmaster for the SF Chapter of the California Native Plant Society; he grows & propagates all of the manroot species native to California. Interested readers can check out his web page about manroot.
Kipp shared a little more with us, and I’m grateful that he did:
“There are two species of manroot you’re likely to encounter in the Bay Area: Marah fabaceus and Marah oreganus. M. fabaceus is called California Manroot and grows more or less throughout the state. Marah oreganus is called Coast Manroot and grows nearer the coast from Santa Cruz County northward. So, right off the bat, M. macrocarpus is ruled out – it ranges only as far north as Santa Barbara (or so).
As for identifying your particular photos:
The top image in your post was taken in the hills above Cupertino where both species grow. What distinguishes M. oreganus is the maple-like, rough leaves. M. fabaceus leaves have very straight edges on their lobes and the leaves are usually smoothish looking (from a distance that is – up close they have minute whiskery bumps).
The bottom image was taken in the East Bay. There is an isolated population of M. oreganus in the hills above Berkeley and Oakland – associated with the relict Redwood forests there – but otherwise East Bay means M. fabaceus as no other species grows in that area. As mentioned above, the leaves in the lower image are straight-edged and smoothish – a very technical term
. The fruit is also helpful as M. oreganus fruit is usually striped with dark green, has sparse spikes and tapers to a point – the fruit in your picture is the round, untapered and densely spiked form typical of M. fabaceus.
Seeds, when it comes to these 2 species, are the most diagnostic: M. oreganus has unique flattened seeds shaped kind of like a hockey puck. M. fabaceus has, like most of the other Marah species, smoother, bullet-shaped seeds.
Marah are extremely variable and where the ranges overlap they freely interbreed. Even individual vines will have very multiple different leaf shapes. This can make identification difficult for individual plants – but you happen to have taken pictures in locations, and of distinct-enough specimens, that the ID is fairly easy in this case.