Rent Shop Volunteer Join

Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
See a list of all Smarty Plants questions

Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

Need help with plant identification, visit the plant identification page.

 
rate this answer
Not Yet Rated

Friday - June 06, 2008

From: Austin, TX
Region: Southwest
Topic: Cacti and Succulents
Title: Leaves turning black on Agave americana
Answered by: Barbara Medford

QUESTION:

Dear Mr. Smarty Plants- We have a ~5-year-old agave americana that began to have leaves turn yellow (to black in some areas) just this past spring (2008). A neighbor's tree had started to overhang the plot it was in, putting it in substantial shade, so I cut away several large branches from the tree, thinking that lack of sun could be part of the problem. Is there anything else I can do?

ANSWER:

We really hate it when someone asks us about an obvious problem with a plant, and when we do research we are told this plant has "no serious pests and diseases," which is pretty much what we got on your Agave americana (American century plant) spots. One thing we did find out, from our own webpage (link above) is that the Agave can tolerate light shade, but really needs sun. But, we did find two websites that admitted there could be anthracnose, a fungal disease, in agaves that could cause those spots.

Michigan State University Extension Agave Disease Problems

Arizona Cooperative Extension Problems and Pests of Agave - This is a PDF document, and you will have to page down to Page 6, lower right hand column, for "Fungal Lesions." Anthracnose of agaves is discussed as a problem during moist conditions or occasionally when the garden is overhead irrigated, as in a sprinkler system or too much rain (hardly a problem right now in Austin). Unfortunately, a plant in too much shade will be more prone to fungal diseases because the sun would ordinarily retard the fungal production, drying out the moisture on the plant. The advice given for treatment is to remove the diseased leaves. And let us warn you, we have discovered that there can be severe and uncomfortable skin blistering from contact with the juices in the leaves when they are cut. Go prepared in long pants, long sleeves, heavy leather gloves, closed-toe shoes and maybe even protective goggles. Once a leaf has gone black, you can be pretty sure it is dead and needs to be removed and disposed in such a way as to prevent further spreading of the fungus to other succulents. This site did suggest one possible chemical treatment, but stated that its actual efficacy is not substantiated. We tried to find pictures of agaves with the anthracnose spots, so you could compare them to your plant, but were unsuccessful. In summary, more sun, less water, and cut out the affected leaves - VERY CAREFULLY!

 

More Cacti and Succulents Questions

Dividing and planting Yucca and pups in New Mexico
June 23, 2009 - I bought a Yucca plant and had 7 plants in one planter 1 large and 6 small. We wanted to split up the plants so we carefully separated them and planted them. My soil is very sandy (Rio Rancho) but I...
view the full question and answer

Mystery cactus in Williamson County, Texas
May 27, 2008 - We have a cactus plant on our place that I have not seen anywhere else in central Texas. The flowers are bright yellow with wine-red centers, but very sparse--only one flower blooms at a time. The p...
view the full question and answer

Native perennial winter plants for Waco, TX
November 03, 2004 - I live in the Waco area, and would like to know winter plants that I could use that would come back each year, flowering or otherwise.
view the full question and answer

Replacements for photinia from San Antonio
August 31, 2012 - i just read your response to someone regarding Red Tip shrubs. You just saved me thousands of dollars ! I was getting ready to order over 250 of these to line my 2.5 acre fence line. What shrub would ...
view the full question and answer

Possibility of growing Buckleys yucca in South Carolina
February 03, 2008 - I live in Lexington, SC. I am wondering if I can grow Buckley's yucca (yucca constricta) here and if so, where can I purchase the seeds or plants? I am from Texas and we are trying to create a "we...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.