Petunias are beautiful, quick, and fun to grow. Here’s how to keep them pretty all summer.
Trude visited us the other day. She said, “John, you said you would tell me how to grow a well-shaped petunia, but you never did.”
I reached for the pruning shears and led her over to a nice plant that needed a bit of care. I handed her the camera and then cut a tip from a stem that was getting too long. “It’s sort of like giving the plant a hair cut.
I cut another tip and then another. Trude said, “I usually just cut mine way back in June or July after it gets stringy and stops blooming but it never does well after that.”
I replied, “I like to trim them every three weeks or so—just about when I notice that they are getting straggly. This does several things, it makes the plant more compact and therefore much stronger, it increases the number of leaves that are available to make food for the plant, and it furnishes more and healthier blooms. This sort of pruning also takes care of the need for dead-heading.”
I pointed. “When the tips are removed, all of the growth that is developing on the stem will begin to grow out and develop. With good care, this growth happens quickly and the plant will be back in full bloom in a week or two.”
Trude reached in and removed a dead bloom, “I always go through and remove all of these,” she said. She showed me the dead bloom.
“You didn’t get the ovary,” I replied. She looked at me with a question asked by raised eyebrows.
I thought for a moment, “Here’s the concept,” I began…
This plant is an annual. It seems to know that it has only one season to grow and reproduce so it makes lots of blooms. When these blooms have been pollinated and when the ovaries are full of developing flower seeds, the plant’s chemical sensors relay that its job has been done. When the plant has made plenty of seeds, it doesn’t see a need for more. It’s sort of like a lady who had several children but wanted a daughter. She tried one more time and got twin boys. She said, “It’s time to stop.”
I pinched off a flower and set it in her hand. “Look closely at the lump at the bottom of the flower. This is the ovary where the seeds are formed. If you just remove the flower and not the ovary, you haven’t really accomplished anything.”
I finished cutting the tips from the plant. “If you just cut the tips carefully, you will accomplish the task of dead-heading and shape the plant at the same time.”
Here is the plant after I practiced proper petunia pruning procedures:
“To keep the petunia growing strongly, I like to give it lots of light and to feed it every couple of weeks with a well-balanced plant food. If your plant is in a Mother’s Day hanging basket, you may wish to put it in a larger container to give the roots plenty of room to grow.”
You may also want to read my article titled “The basics of pruning.”
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johntheplantman--Gardening 
This guy KNOWS what he’s talking about!!!And he makes it interesting as well…great writer!
Oh, I so dislike petunias; but we must plant them in the more popular of the public spaces. Fortunately, they do remarkably well here. I would think that the shade would be a bother. We get help for deadheading and pruning. I did the planting, which is the easy part.
Petunias do have their place, Tony. Of course, my absolute favorite is the dragon wing begonia. I use it in beds and pots for dramatic effects.
Ha! That thing is so rad! but weird too. My colleague down south grows it. I cut it back annually (if I am there at the time), and it is such a waste to discard so much of the scraps. He can only grow so many copies of it.