Excerpts from Jim Conrad's
Naturalist Newsletter

from the December 31, 2017 Newsletter, with notes taken in mid October near Tepotzlán, Morelos state, MÉXICO
Elevation about 5315 ft (1620m), at 18°59′07″N 99°05′59″W
TACACO VINES GONE WILD

During my mid-October visit with a gardening friend in Morelos State, in the high-elevation volcanic belt just south of Mexico City, a certain vine caught my attention. It grew rampantly over my friend's brush piles, and regularly had to be pulled off ornamental evergreens, or they'd cover the trees completely, blocking off sunlight, and kill them. Below, you can see one of the vines just beginning its attack on an ornamental:

Tacaco, SECHIUM TACACO

With its viny habit and large, soft, hairy, deeply lobed leaves, it looked like a member of the Squash/Gourd/Cucumber Family, the Cucurbitaceae. The flowers' corollas were fleshy and yellowish, typical of the Cucumber Family, but their small size and arrangement at the tips of long peduncles was a bit unusual for that family. Even more peculiar were the flowers' bases, each blossom equipped with ten bulging glands forming a kind of knobby crown atop the dangling flowers, as shown below:

Tacaco, SECHIUM TACACO, male flowers showing glands

A close-up of a male flower shows the typical cucurbitaeous feature of the stamens' filaments fused into a column, atop which the clustered anthers form a yellowish, globular mass, as shown below:

Tacaco, SECHIUM TACACO, male flower from side

A frontal view into a male flower appears below:

Tacaco, SECHIUM TACACO, male flower from front

Despite the vines having completely covered certain areas of unused land -- the vines can reach 6m long (20ft) -- I couldn't find female flowers. That's a shame if only because it's the female blossoms that produce fruits, and it's the fruits that this vine is known for.

The vine turned out to be very closely related to the famous Chayote vine, Sechium edule, which produces astonishing numbers of highly edible, easily grown, pale greenish squash such as those shown on our Chayote page at http://www.backyardnature.net/mexnat/chayote.htm

Our plant belongs to the same genus as Chayote. It's SECHIUM TACACO, in English usually called Tacaco. It's native to Costa Rica, but grown in Mexico for its fruit, and sometimes plants escape, as at my friend's place. My friend doesn't grow it, but he does buy ornamental plants from many sources, so possibly his "infestation" is from one of his purchased plants.

The Tacaco fruit, I read, are green, slightly spiny, and when fully ripe may still be very fibrous, and contain a seed that's too bitter to eat -- even hard as stone, according to one writer. However, immature fruits boiled in water are edible, with a flavor that some find reminiscent of artichoke. The fruits are ±pear-shaped, and average about 5cm long (2in) and half as broad.

In Costa Rica certain people are exceedingly fond of Tacaco fruits, but it seems that Mexicans generally think that if you can so easily grow and eat Chayote, why bother with Tacaco? Besides, as my friend's orchard shows, Tacaco vine can go wild in an aggravating way.