En EspaŅol
Share

Ask Mr. Smarty Plants

Mr. Smarty Plants - Failure to thrive of Magnolia grandiflora in Las Vegas NV

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
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.

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

Grafting Pecan Trees
July 05, 2013 - I have planted two pecan nuts and now they are about 4 feet tall trees, they have not been grafted but can I graft one of the trees to the other and vice versa and expect pecans from then, they are he...
view the full question and answer

Problem with baldcypress tree
May 27, 2011 - Two of my three 20 year old Bald Cypress trees appear to have leafed out but are now brown in parts of the tree. The brown area is at the tops of the trees which are probably 40 ft. high. They were...
view the full question and answer

Smarty Plants on women trying to conceive
July 10, 2005 - RE: Eucalyptus. Is this bad for women trying to conceive? The smell is very powerful.
view the full question and answer

Do leaves with tannins make good compost from Austin
November 04, 2010 - I have a couple of old native pecan trees in my (or neighbor's) yard that drop bushels and bushels of leaves every fall. Somewhere in the back of my mind, I have a recollection that pecan leaves have...
view the full question and answer

Propagation of Mexican olive in Luling, TX
August 04, 2009 - Mr. Smarty Plants: we live in Luling, just south of Austin and have a 4 year old Mexican Olive tree; question: how do we propagate this 'hard to find' tree? Thank you so much.
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP
© 2014 Lady Bird Johnson Wildflower Center