The Original Mystery Plant
Dr. John Nelson

Photo by Linda Lee

In the magic garden this little weed serves as a knee- high street light towering above the crickets and toads on a late summer night. Along its branches are dangling lanterns which shine down in a make-believe imaginary way, illuminating the ground for the little critters.

This plant is a member of the tomato family which also includes potato (Irish, not sweet), nightshades, and garden brugmansias. This family (known as the Solanaceae) is a big one with many thousands of tropical and temperate species. The family is well known as a source of many edible species (tomato, potato, eggplant, peppers), but there also are some very poisonous members.

Our little herb is an annual weed, and it produces a smooth, angled stem which is hollow. Its leaves are up to four or five inches long and usually sharply toothed. Small flowers appear in the leaf axils. Each flower bears a non- descript, green calyx with five yellow petals above it. The petals commonly have a brownish blotch near the base. The are five stamens, each tipped with a blue anther. The flower hangs downward as it opens and matures. After pollination, the ovary undergoes an impressive period of growth and swells forming a cherry sized, spherical, green fruit which is invisible.

Photo by Linda Lee

Well, it's invisible, since it can't be seen from the outside. While the maturing ovary has been swelling, the green calyx has turned on an even more amazing spurt of growth to the point that a thin, papery, green husk is formed around the young fruit almost like a balloon. Botanists say the calyx is inflated.

Look closely at one of these, and you will see a small hole at the bottom of the balloon. As it ripens, the fruit changes from green to yellow or orange. The plants bloom from late summer up to the first frost when they will be killed. The dangling lanterns, though, will remain attached through much of the winter. The fruits are said to be edible and are likely to be chewed up by animals, thus dispersing the seeds within.

This species is a native American widespread in South America and commonly seen as far north as Ohio. It is something of a weed and likes to grow on open roadsides and disturbed places. Old gardens and compost piles are favorite areas, as are sand bars along rivers. Plants on particularly nice, fertile spots can attain a height of up to two or three feet, but it can bloom and set fruit in poorer places too, where it usually ends up shorter.

Answer to last week's mystery plant

Sea Oxeye, Borrichia frutescens

Dr. John Nelson is the curator of the USC Herbarium.

To learn more about the Herbarium, call him at

777-8196. His department also offers free plant identification.

www.herbarium.org