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?

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
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
6 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

QUESTION:

What causes yellowing of native garden plant leaves?

ANSWER:

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 Compost and Mulch Questions

Transplanting yucca pups from Dallas
September 01, 2010 - Can I transplant Pup Yucca plants off of the main yucca and how do I cut them off?
view the full question and answer

Older leaves yellowing on Savannah holly in Dallas
May 01, 2009 - I planted a Savannah Holly in Dallas, TX in the Fall of 2008. It has new growth and some white buds all over it, but some of the older leaves are turning yellow and dropping off. Is this normal?
view the full question and answer

Allelopathy of American elms from Dallas
March 24, 2013 - Are American elms at all allelopathic?
view the full question and answer

Oak leaf hydrangeas from Edwardsville IL
August 13, 2012 - Hello, I live in West Central Illinois (across the river from St. Louis) and I am considering planting several Oak leaf Hydrangea's in my yard. The location where I would like to plant them is und...
view the full question and answer

Ants in the compost pile from Georgetown TX
March 09, 2012 - Can you give me any suggestions for ridding my compost pile of ants?
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