En EspaŅol

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?


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
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
4 ratings

Tuesday - December 04, 2007

From: Phoenix, AZ
Region: Southwest
Topic: General Botany, Watering
Title: Effect of epsom salts and gray water on plants
Answered by: Nan Hampton


We live in Phoenix where water is a precious commodity. We have decided to use as much of the gray water as we can for watering our garden, shrubs and trees. One of the suggestions we heard about was to use the water from the bathtub. We were wondering if the Epsom Salts(magnesium sulfate-MgSO4.7H2O) that we use in the bath water is harmful to the plants and/or trees?


Well, unless the concentration of epsom salts in your bath water is very high, it will probably be beneficial to your plants. Both magnesium and sulfur are necessary plant nutrients. Plants need magnesium for the production of chlorophyll and, therefore, it is necessary for photosynthesis. Magnesium is also important in activating many enzymes. Sulfur is a component of some amino acids and is also a component of some enzymes. You can read more about the effect of epsom salts on plants in:

What is the effect of epsom salt on a plant? and How does epsom salt affect plant growth?

Generally, the level of each of these nutrients in soils is high enough for the plants' health. However, sometimes soil has low levels of Mg and/or S and, in that case, epsom salts are recommended as a fertilizer.

You can see recommendations from basic-info-4-organic-fertilizers.com for proportions for the application of epsom salts as a plant supplement. You can compare these proportions with the concentration of epsom salts in your bath water. If your bath water isn't more concentrated, then your plants will probably benefit from its application—not only for the moisture but for the added nutrients as well.


More Watering Questions

Failure to thrive of desert willow in Wimberley TX
August 10, 2010 - I have a desert willow. It is always, whether I water it or leave it alone, yellow/ brown leaves, dark spots on the leaves, losing leaves. now it looks sad and not very healthy. Can you please tell m...
view the full question and answer

Care for non-native 'Glacier Blues' from Charlton MA
March 24, 2012 - Do you have to prune or cut down Glacier Blues in the garden? My plants look brown and wilted.
view the full question and answer

Failure of Bald Cypress to fully leaf out
April 14, 2008 - My family just moved to a house in Burnet County, about 7 miles south of Bertram, close to the Balcones Canyonlands NWR, with very rocky limestone soil. We bought several trees last fall, including a ...
view the full question and answer

Trumpet Vine Dropping Buds
July 25, 2013 - My trumpet vine is dropping its buds before flowering. This happened last year as well. Do you know what is causing this and what I can do to prevent it?
view the full question and answer

Limp leaves on Texas purple sage in Magnolia TX
July 22, 2010 - Recently planted Texas purple sage, some of it looks healthy and has new blooms, but a few of the plants have limp leaves and are thin at the bottom. I read the article on cotton root rot, but am not ...
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.
© 2015 Lady Bird Johnson Wildflower Center