Wild cucumbers climb high this year
A neighbor called last week asking if an extra-terrestrial plant species has invaded recently. He said that rapidly-growing vines with maple-like leaves, tightly coiled tendrils, many small white flowers and spiky seed pods are growing all over his trees.
I told him they are wild cucumber vines, a native plant widespread in North America. They aren't kudzu, the invasive Asian vine that covers trees down south.
Wild cucumber, Echinocystis lobata, is a member of the gourd family. The genus name refers to the prickly oval-shaped fruit.
Wild cucumbers are annuals, germinating from seeds each year. The non-woody vines grow rapidly with three tightly coiled tendrils growing from each leaf axil. The tendrils grasp other plants tightly and are very tough. The leaves have five to seven points and resemble domestic cucumber leaves. The vines can clamber 15 to 25 feet up trees.
Panicles of small male flowers occur in spikes about six inches long. The flowers are about half an inch across with six white petals, a green center and yellow pistil.
At the base of each panicle of male flowers is a female flower with its stalk attached to a leaf axil. The white female flower is above a spherical spiky ovary. After fertilization, the ovary develops into the spiky globular fruit bearing four dry seeds. Unlike many other plants in the gourd family, the fruit of wild cucumbers aren't edible.
The mature fruit are about two inches long. The long prickles aren't very strong and will bend without penetrating your fingers. They may serve to keep birds from eating the seeds. As the fruit dry out, the webby structure protecting the seeds becomes apparent. The fruit open up at the bottom and the seeds fall out to the ground to germinate next year.
Wild cucumbers can grow vigorously, climbing over and covering trees and shrubs. They grow in abundance around the edges of our yard, often covering parts of evergreen trees. You can pull them when they are small but they become hard to remove as they become larger vines with many tenacious tendrils hanging onto their support tree.
The warm and moist summer stimulated growth of wild cucumbers this year. We pulled them off our ornamental evergreens near the house and off a few apple trees. They are interesting-looking plants however. Their flowers and spiky seed pods mark the end of summer.
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