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
7 ratings

Tuesday - May 06, 2008

From: Georgetown, TX
Region: Southwest
Topic: Compost and Mulch, Diseases and Disorders, Watering, Herbs/Forbs
Title: Yellowing leaves
Answered by: Barbara Medford


What causes yellowing of native garden plant leaves?


You may be overwatering them. On the other hand, you may be underwatering them. Isn't that wonderful? Some of the causes are environmental, as this information from a website by Suite 101 indicates.

Too much water in the soil will prevent oxygen from getting to the plant’s roots, thereby smothering them. As roots die, the foliage above ground starts to discolor and die. Overwatering also promotes fungal root diseases such as armillaria and phytophthora.

Under watering will cause leaves to wilt, fade in color to a dull shade, and drop prematurely. The new growth at the tips of the plant may wilt in the afternoon and then recover in the evening. If the plant is under prolonged stress from lack of water, new leaves will be smaller and the plant will become increasingly susceptible to insects and disease.

If a plant is lacking in iron, new foliage will be small and it will fade to a yellowish green, starting at the edges of the leaf and spreading inward until only the veins remain green. If the plant is lacking nitrogen, older leaves will uniformly turn yellow.

To correct iron-deficient soil, aerate the soil around the roots and spread an iron chelate evenly over the soil beneath the plant canopy or apply it to the foliage, according to the product label. If you regularly mulch with composted organic matter, you will eventually remedy the iron deficiency.

A nitrogen deficiency can be fixed quickly by applying a nitrate fertilizer but this will tend to promote more rapid, succulent growth, which attracts aphids and mites. An organic form of nitrogen, such as compost, which must decompose before being absorbed by plants, will prevent the excessive growth.

Another reason may be where you are in the growing season. If leaves are through growing, they will begin to turn yellow, and be replaced by fresh, new green leaves. At the end of the growing season, the whole plant may begin to yellow.

So, we really haven't helped you much, have we? If a lot of your plants have a lot of yellow leaves, we'd say you had a drainage problem. Either the water is going into soil, like sandy soil, that drains too fast, and leaves the plants dry, or into clay soil, where it stands and begins to suffocate the roots. We would suggest going the aerating and composting route suggested above, because that will really fix all the problems. If just a few leaves here and there are yellow, it's probably not a big concern, but the organic mulch is still a good idea. It's something that is good to do on all your plants, over time, and makes them healthier.




More Herbs/Forbs Questions

Plants for north side from Dale TX
February 10, 2012 - What native trees and bushes can I plant on the north side of house? Can I use corn meal( I NEED FIGHT A GRASS) in flowerbed and then plant native wildlife seeds(FLOWERS)?
view the full question and answer

Plants indigenous to Sedona, AZ
July 07, 2010 - I live in Sedona AZ and I want to plant indigenous plants in my garden. Is there a list of AZ native plants shrubs and trees that are indigenous to Sedona? If there is no list that is specific f...
view the full question and answer

Groundcover for Laredo Texas
July 04, 2011 - I am in Laredo, TX and no longer want to waste water on grass. I would like to pull it all out and plant native, drought resistant ground cover - low growing, between 6-12 inches, sun and partial sha...
view the full question and answer

Optimal time for trimming Fall asters
July 04, 2014 - RE: fall asters What is the latest date in the summer that I can trim my fall asters and still get a good amount of blooms in October?
view the full question and answer

Need to stabilize a south facing slope in Henderson, NC
April 30, 2010 - Hi, I have a south facing slope that is heavy clay with rock under it. It gets a lot of sun. I have planted a few bushes and some ground cover, but with all the snow and rain we had this past winter, ...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.
© 2015 Lady Bird Johnson Wildflower Center