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

Trimming freeze-damaged Agave Americana in Alvarado TX
April 08, 2010 - What is the best way to trim Agave Americana cactus? The freeze this winter when it snowed has caused the leaves to die towards the bottom of the plant.
view the full question and answer

Damage to Yucca rostrata from Nottingham, England
February 26, 2014 - Hi, I have a yucca rostrata which has had its head snapped off in high winds (we live in Nottingham, England) we have left the trunk in the ground, will this re grow?? What is the best thing to do wit...
view the full question and answer

Plants for area around salt water pool
June 27, 2013 - What are some plants that will grow around my salt water pool where there is some salt water runoff occasionally.
view the full question and answer

Sunny and shady lawns from Austin
April 28, 2012 - My front yard has a large bed surrounded by a mix of St. Augustine and Bermuda grass. Last summers heat killed off about 90% of the St. Augustine, which we would like to replace anyway to conserve re...
view the full question and answer

Plants for planting in gourds
March 15, 2009 - I enjoy painting dried gourds. This spring I got the idea to paint a gourd and cut holes in the side and plant some small blooming flowers. I have seen "hen and chickens" growing out of holes in the...
view the full question and answer

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