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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.

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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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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!

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Monday - April 29, 2013

From: Pacific Plsds, CA
Region: California
Topic: Invasive Plants, Cacti and Succulents
Title: Runaway Agave Americana from Pacific Palisades CA
Answered by: Barbara Medford

QUESTION:

We live near open space on Santa Monica Mountain State Park. Our Association planted non-native, invasive Agave Americanas all over the adjacent slopes, and we are trying to get the exploding pups and forest of mature ones removed, or controlled. Three are now sending up stalks. Can we prevent seeding if we remove the individual flower stalks before they dry and split open? The rhizomes are bad enough, but seeds could more easily spread to our precious park land. I'd much appreciate some advice. Thank you for all you do. We have seen Mrs. Johnson's works in our, and other states. Jill Bowman

ANSWER:

We don't quite know how to tell you this, but not only is Agave americana (American century plant) native to California but, according to this USDA Plant Profile Map, it is also native to Riverside and San Diego Counties, which is close enough to be considered native to the area. We found no indications that it was considered invasive, but you might want to read this Dave's Garden Forum page with several negative comments on the dangers of trying to remove it.

In answer to your  question on taking down the bloom stalk before it seeds out, you can certainly do so, but you will miss quite a show if you don't let the bloom stand for a while. And, the plant is going to die anyway. Century Plants live for from 8 to 40 years (not a century) before they bloom and, once they have bloomed, they die. They have been storing up the energy to reproduce all those years and then they are done.

You didn't say what Association planted the agaves, but if they are on State Park land, it would be up to the management of that park to determine whether they were to be removed and how it was to be done.

Here are links to some previous Mr. Smarty Plants answers on removing an agave:

Removing the pups

Removing the mother plant

Reasons to remove an agave

Cutting the stalk off

Bottom line: Cutting down and destroying the blooming stalk will certainly prevent seeding any more agaves, but the pups around those plants are the main source of propagation for the plant. Attacking any of those projects means attacking the mature plants, which is going to be plenty tough.

 

From the Image Gallery


American century plant
Agave americana

American century plant
Agave americana

American century plant
Agave americana

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