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
Not Yet Rated

Sunday - June 09, 2013

From: Liberty Hill, TX
Region: Southwest
Topic: General Botany, Non-Natives, Compost and Mulch, Soils
Title: Problem With Vegetable Garden Soil
Answered by: Mike Tomme


We live in Liberty Hill on 25 acres and we are working to restore native grasses and plants. We are ardent supporters of the Wildflower center. I say this because my question is not "typical" of what I follow. We have spent an inordinate amount of money putting in raised beds this year for veggies. The gourmet soil mix came from respected organic gurus. We planted in March-plants came up then atrophied. We replanted and now we have pale, emaciated "bonsai" plants. Soil tests show no nitrogen. We added manure, blood meal. The supplier does not believe us. Question: what could possibly make gourmet soil so toxic? Not one plant has grown.


Normally, Mr. Smarty Plants doesn’t answer questions about vegetable gardening, but since you are an ardent supporter of the Wildflower Center, I’ll make an exception. Besides, I think I know the answer.

First let’s talk about your soil test. It is highly unlikely that your soil has “no nitrogen.” Was this a soil test from the AgriLife Extension Service or a home test kit?  If a home test kit, I highly recommend  you get  a “real” test done by AgriLife Extension.  I strongly suspect you have a nutrient imbalance and it is important that you find out where you stand with your soil.

However, I suspect that your problem lies with phosphorus rather than nitrogen. Commercial garden soil mixes typically contain a lot of compost which is high in phosphorus. The AgriLife Extension Service has a publication entitled Phosphorus: Too Much and Plants May Suffer. This is the opening paragraph of that publication:

“The buildup of phosphorus in lawns, gardens, pastures and croplands can cause plants to grow poorly and even die. Excessive soil phosphorus reduces the plant’s ability to take up required micronutrients, particularly iron and zinc, even when soil tests show there are adequate amounts of those nutrients in the soil.”

The report goes on to talk about corrective measures. I recommend you read the whole thing, but I’ll summarize the main steps:

1. Avoid future applications of phosphorus by eliminating organic composts and manures.

2. If nitrogen is required, use low phosphorus sources like blood meal.

3. Apply iron and zinc by foliar application.

The report goes on to discuss how long it will take to clear up the problem. Unfortunately, it will take years (3 to 5 years is their estimate).

I have personal experience with this problem. I built raised beds and blended my own soil, using lots of compost (no one ever told me you can use too much). My plants experienced problems almost exactly like you describe. I have been doing foliar applications of a solution of iron and zinc (available at many garden centers) and have been adding nitrogen to the soil (I use ammonium sulfate because my dog digs it up if I use blood meal). So far, it is working. My plants are much larger and more vigorous than before I started. But, if I get lazy and don’t do the foliar application on time, they start to droop and turn yellow. 


More Soils Questions

Native plants suitable for clay soils in College Station, Texas
November 26, 2013 - Where might I find a list of native plants suitable for clay soils in the College Station TX area?
view the full question and answer

Replacing hawthorn bush with muhly grass from Plano TX
April 10, 2014 - I am thinking of replacing a hawthorn bush with a muhly grass plant or two in an edged area with river rock cover in Plano, texas. It is the black soil and not a sandy loam. We have a sprinkler syst...
view the full question and answer

Yellowing leaves on Carolina jessamine from Las Vegas NV
March 21, 2014 - Carolina jessamine, has yellow leaves. 3 years old, grows on south wall, full sun. Same plant, in partial shade, has green leaves. Should I feed yellowish plant some nitrogen? If yes how much?
view the full question and answer

Privacy screen shrubs for Butler PA
August 09, 2013 - Here is what I want in a bush: native to Western Pa.(Southern Butler County), appropriate for a horse pasture,fast growing, not too aggressive (I will mow around it regularly and can prune occasionall...
view the full question and answer

Plants for heavy clay in Sonoma County, California
July 10, 2013 - Hi, I live in Northern California, Sonoma County, and would like to transition my front garden into mostly native plants. Trouble is, my soil is clay, yicky, heavy clay, and some of the natives I've ...
view the full question and answer

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