Last updated on December 2nd, 2011
Container-grown petunias, usually picture-perfect in June, are often on the weary-side by July, and half-dead come August. This is how you can perk them up again:
With scissors or hand-pruners, cut stems back by one-half to two-thirds. Then, with a kitchen fork, loosen and aerate the compacted soil. Poke gently, however, to avoid injuring roots.
Next, feed with one half-tablespoon of a high-phosphorous plant food dissolved in one gallon of water. Apply this formula daily, and you will see new growth and sweet blooms within a few week’s time. 
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Samantha says
Kevin, just the news I needed. Thanks for the tip. My petunias have grown stringy, and they look just horrible.
I'll give them a haircut today, but I have one question: Is a high-phosphorous food the same as a “blossom booster?”
Macy says
As August has worn on, I had just about given up on my petunias. I am delighted with your tips and will give it a whirl. Macy
Kevin Lee Jacobs says
Samantha – yes, formulas that say “Blossom-Booster” are indeed high-phosphorous. Phosphorous is the middle NPK number on the package label; look for 10-30-20 or something similar.
Macy – welcome! I'm so glad you can use this petunia-tip!
Samantha says
Haircut and fertilization accomplished. The stringy stems in my basket of deep purple petunias are a fraction of their former selves, but already they look vastly improved!
Janis says
Kevin, thanks for republishing this post. AFter the horrid heat and humidity here in Chicago, my petunias look like sh*t. I'll do as you say, and hope for the best.
LindaK says
I got several colors of wave petunias years ago in hanging pots and I just kept them from year to year by letting them freeze out and then bringing them out in the spring to grow up from seed. I have to pull some out, as they are too dense, and replant them somewhere else. This past year when it was so horribly hot and dry I had the most beautiful petunias I’ve ever had because I kept watering them every day and gave them liquid fertilizer about every other day. I had gorgeous blooms going strong until the freeze got them late in winter. I’ve saved hundreds of $$$ by this method. They always generously re-seed and they even kept the little birds happy with seeds.
Kevin Lee Jacobs says
LindaK – That has been my experience with petunias, too. They are great re-seeders (and hence, ideal candidates for winter-sowing).
Christine says
Thank you so much for this tip. I have a large container of powered blue Miracle Grow, do you think that would help rather buying another product? Tomorrow I will trim the poor thing, thanks! And loosen up the soil too.