En EspaŅol
Share

Ask Mr. Smarty Plants

Mr. Smarty Plants - Yellowing leaves

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

Fruit in the compost bin
June 07, 2009 - I have a compost bin and I use the pulp from fruits and vegetables as one of the ingredients in my compost pile. We juice everyday so will all this pulp be too potent for new seedlings?
view the full question and answer

Turf grass for part-time home from Louisville KY
April 28, 2012 - We have a small yard at a remote location with cistern water, and need a turf grass for a yard, clay soil, which I am willing to amend. It will receive sporadic attention as my husband and I do not l...
view the full question and answer

Gardening advice for Quebec
April 15, 2011 - I live in Aylmer Quebec 1. I bought some lily bulbs at a Christmas bazaar. When can I plant them and what do I put in the hole with the bulbs? 2. I bought a little potted cedar at COSTCO for a Ch...
view the full question and answer

Freeze damage to esperanza in pot from Brady TX
December 10, 2009 - My esperanza, currently in a container, has suffered some freeze damage. I have prepared a planting spot for it and am not sure whether to plant now, trim it back if I do plant it, etc. I would appr...
view the full question and answer

Plants for small shady area with clay soil
August 09, 2011 - Many people have space between the sidewalk and the street in front of their homes. In that space in front of our house is a growing maple that provides a lot of shade. The space is very dry, with...
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