Lycianthes asarifolia--a new weed in Texas

Click on the thumbnails to view a full-size image

In July of 1997, an unknown plant was collectd in a Houston neighborhood and sent to the Texas Agricultural Extension Service for identification. Next, the Texas A&M Biology Department Herbarium was called in. Finally, with the help of Mike Nee at the New York Botanical Garden, the plant was positively identified as Lycianthes asarifolia.

This plant is a member of the Solanaceae, the family which includes potatoes, tomatoes, peppers, eggplant, and nightshade. Lycianthes is a genus of 150 to 200 species largely native to Central and South America. L. asarifolia is native to Venezuela, Bolivia, Peru, Paraguay, southern Brazil, and northeastern Argentina (De Rojas and D'Arcy, 1997). How it arrived in Houston is not known at this time, but it has been there for at least three years.

How can I identify Lycianthes asarifolia?

L. asarifolia can be recognized in part by its prostrate habit--the stems run at ground level and root at each node. The leaves are long-petioled, heart-shaped, and quite variable in size. In the Houston plants, the leaf tip is rounded, but pointed forms are known. There is often only one leaf per node, but a second is sometimes present. When the primary leaf is relatively large, the second is usually very small and stipule-like; when the primary leaf is relatively small, the second leaf is often nearly the same size.


The flowers are solitary at the nodes, nodding on stalks a little shorter than the leaves. The blooms are 1/2 to 3/4 inches broad. The calyx is truncate, has 10 nerves, and tends to persist in fruit. The corolla is white and rotate--the 5 petals are strongly united. The five stamens are grouped around the protruding style. The yellow anthers open by pores at their tips. The fruit is an edible reddish-orange berry about 1/2 inch in diameter.

Why all the fuss?

This plant has overrun seveal yards in Houston, forming a dense ground cover that can out-compete St. Augustine grass in shaded areas. It is reproduicng both vegetatively and reproductively, and may also be spread via seeds and plant parts carried from yard to yard on the equipment of landscape maintenance companies--and through drainage ditches in the neighborhood. The residents' attempts to eradicate this plant by hand-pulling, herbicide application, and sod removal have all failed. This perennial plant has demonstrated an ability to survive several hours below freezing and dies back only in the hottest summer weather. It has the potential to become a serious weed in large parts of Texas. For example, should it become established in nearby Memorial Park, it could be nearly impossible to get rid of. It certainly has the potential to compete effectively with native species.

Note that this species has been seen in North America before, in New Orleans (Darwin and Feibelman, 1991). De Rojas and D'Arcy (1997) mentioned plants in Texas--this was an error; they refer to the Darwin and Feibelman article. However, the Louisiana population, as far as is known, has not produced any fruit and is not as rampant as the Texas plants. The species is self-infertile, so perhaps the Louisiana population represents a self-sterile vegetative clone.

What should I do if I find it?

It is very important that any other populations of this plant be identified, documented, and destroyed. First, contact either Mary Ketchersid or Monique Reed at the addresses given below. They can help you positively identify the plant and give you some advice on how to try to get rid of it. Please do not send live plants or fruit through the mail or give them away--it may look like a harmless ornamental, but it's really a noxious pest.

Contacts

Monique ReedMary Ketchersid
Herbarium BotanistAgricultural and Environmental Safety
Biology DepartmentTexas Agricultural Extension Service
Texas A&M UniversityTexas A&M University
College Station, TX 77843-3258 College Station, TX 77843-7101
monique@mail.bio.tamu.edum-ketchersid@tamu.edu

References

DARWIN, S.P and T. FEIBELMAN. 1991. Lycianthes asarifolia (Solanaceae) new to North America. Sida 14(4)605-606.

DE ROJAS, C. E. and W. G. D'ARCY. 1997. The genus Lycianthes (Solanaceae) in Venezuela. Ann. Missouri Bot. Gard. 84:167-200.

Last updated April 28, 1998 by M. Reed