Contact Us Host an Event Volunteer Join

Support the plant database you love!

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
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

QUESTION:

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?

ANSWER:

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

Wintering Purple Coneflowers in pots in Springfield MO
August 26, 2013 - I have some 8 month old purple cone flowers in containers on my porch. They did not bloom this summer because they were seedlings when given to me. I can not put them in the ground. How can I keep the...
view the full question and answer

Baby mountain laurels are ready to move, in Lockhart Texas
October 19, 2011 - I want to harvest the baby mountain laurel plants which are growing under a large bush. What height would be best for the young plants survival? Please recommend a soil mixture for the pots.
view the full question and answer

Watering Native Trees in Georgetown, TX
July 19, 2012 - I installed a native/adapted plantscape in early March including several small trees. They were planted in the rocky soil west of I-35 in Georgetown with plenty of added compost and mulch. Other than ...
view the full question and answer

Dormancy in Pin Oaks without water in Del Rio, TX
August 02, 2011 - Can Pin Oak trees go dormant without enough water? If so how long can they live that way? Can they be brought back to producing leaves? If yes, then what do I need to do besides giving them water. I d...
view the full question and answer

Resourses that are being taken away - Tiffin OH
April 03, 2013 - What are resources that are being taken away from humans and organisms?
view the full question and answer

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