Tuesday, August 20, 2013

Wild Cucumber - Annoying Native Plant

Key identifiers: fast-growing green vine with tendrils, large leaves, white flowers, green pods/fruit covered in spikes. After fall frosts the vines and pods turn brown, the pods open at the bottom, and large brown seeds fall out. Pods stay attached to vines. Click on photos to enlarge. 

See September 2012 for column on four invasive plant species.

Immature seed pod next to male flowers
Wild cucumber, also known as prickly cucumber and balsam apple, is a plant species native to North America but with the annoying habits of some invasive plants. Key identifiers: green vine, large leaves, white flowers, green pods/fruit covered in spikes.

The species name is Echinocystis lobata. It is a fast-growing annual propagated by seeds. This vine can blanket low plants or tendril its way 15-20 feet up trees. During July and August the slender vines display white flowers, followed by the development of seed pods that superficially resemble a small, spiky cucumber. Once the seed pods mature they dry out and disperse from the bottom several large black seeds the size of pumpkin seeds. Echinocystis dies with the first frosts of fall.

Swathe of wild cucumber next to Assabet River Rail Trail
Lobate leaves, tendrils, and vertical spikes of male flowers, Echinocystis
In Maynard, there is currently a large swathe of wild cucumber growing next to the Rail Trail section that is bound at the south end by MapleBrook Park and at the north end by the Cumberland Farms gas station. The growth occupies a space on the west side where there was an intense brush fire in 2011. The fire opened the area to more sunlight, and also provided fertilizer in the form of ash. The result is a riotous growth of a mix of weedy annuals some four to eight feet tall, draped with the green leaves and white flowers of Echinocystis.

The name comes from Echino for spiny and cystis for bladder-like in appearance. Lobata refers to the shape of the leaves.


Echinocystis is native to the central, eastern and northern states, up into Canada. It is not found in southern California, but confusingly, there are related plants in California and Baja California (Mexico) that also go by the common name wild cucumber.

The latter are in the family Marah. These are also fast-growing vines with tendrils and seed pods that superficially resemble a spiky cucumber, but Marah are perennials, each year's new growth sprouting from a huge tuberous root that can weigh more than 100 pounds.


Maturing wild cucumber seed pods
Although native to North America, Echinocystis lobata is in fact an invasive species in Europe, where it was first introduced as an ornamental garden plant (always the same sad story). This serves as a reminder that not all invasive species move from the Old World (Europe, Asia and Africa) toward the New World (the Americas). Poison ivy plagues England and parts of mainland Europe because back in the 1600s, people thought it was pretty!

Spiked seed pods dry from the bottom up, then peel
apart. The mature seeds (dark color) fall to the ground.
The dry, brown pods remain attached to the vine.


And not all invasive species are plants. Some of the most damaging to have made the crossing from North America to Europe are grey squirrels, raccoon, mink, and lobster. The mammal introductions were deliberate - either as pets or an attempt to develop locally grown animals for the fur trade. American lobsters may have been escapees from seawater holding pens for the food trade or deliberate releases by people who bought live lobsters air-shipped to Europe, and then found themselves unwilling to immerse their purchases in boiling water.  



Dead wild cucumber vines, with seed pods
January 2015: This last photo is a mid-winter view of the same patch of green seen in the second photo. What remains are the dead vines and the brown, emptied seed pods, sort of like nature's string of Christmas lights gone to rot and ruin.

These photos taken along a 1200 foot long section of rail trail in Maynard, MA. What's noteworthy is how fast the wild cucumber went from not present at all to overwhelming other growth. Within five years it went from a plant or two to a major nuisance in the areas of partial to full sunlight. It does not do well in deep shade.

By spring, last year's vines will have rotted under winter's snow. First plants to appear on this part of the trailside include pokeweed and Japanese knotweed. The wild cucumber vines don't really take over until July  

UPDATE: Rail Trail construction in Maynard in 2017 has made it easy to visit the wild cucumber patch, just north of the 1.50 mile marker.

2 comments:

  1. I found your writing with a Google image search today. Thanks for the explanation. I took a photo of these same wild cucumbers (Lobata) growing in a northern IL forest preserve last summer. Then while reading a similar description of a spiny cucumber in a book about Kalahari Bushman, I wondered if this could be the same plant. The Bushman dug it's edible root (perhaps the Marsh variety) for its sustaining liquid during the driest season (according to the book "The harmless people" by Elizabeth Marshall Thomas, p106). M. Ball-Harrison.

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  2. I am not a botanist, but cannot believe that a species native to northern North America is same as one found in southern Africa.

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