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
1 rating

Monday - January 17, 2011

From: Las Vegas, NV
Region: Rocky Mountain
Topic: Trees
Title: Failure to thrive of Magnolia grandiflora in Las Vegas NV
Answered by: Barbara Medford

QUESTION:

I live in Las Vegas, NV and have several Magnolia Grandiflora trees. They were doing well until 2 years ago when they started losing their leaves. The leaves turn brown or very dark on the edges. One landscaper said they need Sulfur from the local nursery. Didn't seem to help. One said more water. Helped for a short time, deep root watering. Any nutrients or minerals I can use to help them. The flowers are gorgeous and I hate to lose them.

ANSWER:

As you will note from this USDA Plant Profile map, Magnolia grandiflora (Southern magnolia) does not grow natively anywhere west of Texas, and East Texas, at that. In part, the accuracy of our answer depends on how recently those trees were planted. If you planted them three years ago, and they started losing their leaves 2 years ago, then we expect that when the tree roots got out of the good dirt you probably planted them in, those roots could not tolerate the soil they found themselves in. If they were planted several years ago, then we are astounded they lasted that long. Take a look at the Growing Conditions from the page in our Plant Database for this tree:

"Growing Conditions

Water Use: High
Light Requirement: Part Shade
Soil Moisture: Dry
CaCO3 Tolerance: Low
Cold Tolerant: yes
Soil Description: Rich, porous, acid soils. Sandy, Sandy Loam, Medium Loam, Clay Loam Clay, Acid-based, Calcareous

Also, from that same page, here are the normal habitats of this tree: "Native Distribution: Coastal Plain from extreme s.e. VA to FL, w. to e. TX."

Doesn't sound a whole lot like Nevada, does it? We're betting that you have alkaline soil, with a Ph above 7, as does most of the western United States. Magnolias need acid soils, as noted above, with a Ph below 7. The sulfur recommended was probably an attempt to help in that situation. But that magnolia tree ordinarily would grow very large, with underground roots to match or exceed the circumference of the top. See this article from Utah State University Extension on soil alkalinity to get a better idea of the problem. If that proves to be the case, it demonstrates again the desirability of using plants native to the area in which you are trying to grow them, which is the goal of the Lady Bird Johnson Wildflower Center. The magnolia has adapted to growing on forest floors, with a rich humus of centuries of fallen leaves beneath them, in part shade and with plenty of moisture.

Las Vegas is in USDA Plant Hardiness Zones ranging from 8a to 9b, and is in the arid Mohave Desert. We can understand your desire for a lovely evergreen tree with big white flowers, but in view of the environmental situation there, where more xeriscapes are being encouraged, a woodland native like the magnolia is not a good choice. We suggest that you contact the University of Nevada Extension Office for Clark County to see what their take on your problem is.

 

 

 

More Trees Questions

Is Ashe juniper (Juniperus ashei) really native to the Texas Hill Country?
October 12, 2010 - I had heard that the Ashe Juniper was not native to the hill country or even Texas. Is this true? What is their history? They sure make it hard for the elms and oaks to thrive. We have decided to re...
view the full question and answer

What are the grey-green plants on oak trees in San Marcos, TX?
March 12, 2011 - The oak trees in the neighborhood in San Marcos, TX, are covered with clumps, or balls, of gray/green fluffy-looking plants. they remind me of bromeliads. You can pull and knock them off; after wind ...
view the full question and answer

Japanese lilac trees in Lehi UT
July 31, 2010 - Dear Mr. Smarty Pants, We live in Utah and this past spring planted three Japanese Lilac Trees in the lawn next to the deck hoping they would one day provide some shade. They are planted in full sun ...
view the full question and answer

Need options for smaller trees in neighborhoods in Austin, TX.
May 25, 2012 - Please discuss smaller tree options for typical Austin neighborhood yards. These houses are built close together on the sides, and only have smallish back yards. They just don't have space for big 50...
view the full question and answer

Evergreen native trees for Austin
January 31, 2009 - Please recommend all evergreen native trees for Austin TX.
view the full question and answer

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