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

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Thursday - July 04, 2013

From: Magnolia, TX
Region: Southwest
Topic: Diseases and Disorders, Cacti and Succulents
Title: Century plant leaves yellowing from Magnolia TX
Answered by: Barbara Medford

QUESTION:

The leaves on my large Agave/Century plant are turning yellow. The bottom leaves, touching the ground are dying. Plant is 5.5" tall, 6" across & approx 10 yrs old. Recently we put red mulch around the plant. Could this be causing it stress?

ANSWER:

There are 10 plants with the common name "Century" plant native to North America, of which 7 are native to Texas. None are native, nor even very close to, Montgomery County, in southeastern Texas. All are members of the Agave genus and, since your plant may not only be not native to your area, it may even be a hybrid or native to Mexico, which means it is not in our Native Plant Database at all. Here are three of the Texas natives, with maps for each from the USDA Plant Profiles, showing in which counties they are native:

Agave univittata (Maguey mezortillo) (Map) native closest to Montgomery County, in Kennedy and Starr Counties on the far southern tip of Texas.

Agave havardiana (Havard's century plant) (Map) native to to Jeff Davis, Pecos and Brewster Counties, in the West Texas Big Bend areas

Agave parryi (Parry's agave) (Map) native to Culberson, Jeff Davis and Brewster Counties, also in Big Bend Area

We mention these locations because we suspect the problems with your agave, whichever one it is, are cultural. Agaves are basically tough desert plants, accustomed to enduring intense heat, full sun and weeks without rain. For instance, here are the growing conditions for Agave havardiana (Havard's century plant), from our webpage on this plant:

"Growing Conditions

Water Use: Low
Light Requirement: Sun
Soil Moisture: Dry
Soil Description: Dry, rocky soils."

We have driven through Magnolia on our way to The Woodlands many times, and our impression of that area is that it is heavily forested, probably with acidic soils from all the leaves and pine needles that have fallen over the centuries, with more shade and more rain than this plant likely needs or can tolerate. This is why we always recommend the use of plants native not only to North America but to the area in which they have evolved because they are already accustomed to the sun, climate and soils of their native area. However, because we can't prove anything we have said, we will look for some research on what could be causing the yellowing and drooping of leaves.

Please read this previous Mr. Smarty Plants question for more information and possible fixes for your plant.

 

From the Image Gallery


Maguey mezortillo
Agave univittata

Havard's century plant
Agave havardiana

Parry's agave
Agave parryi ssp. neomexicana

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