Pruning Petunias – Information On Cutting Back Petunia Plants


By: Teo Spengler

No plant fills a container or bed with glorious colors faster than petunias, the workhorse flowers of the summer garden. But, as is the case in so many relationships, your admiration for your petunias may fade as the first flush of blossoms die and the plant begins to appear leggy and straggly. Even if you deadhead furiously, clipping off all those faded blossoms, the stems just keep growing longer. Read on for more information about how to cut back petunias.

Do Petunias Need Pruning?

Many gardeners view annuals as disposable, and simply don’t know how to cut back petunias. But cutting back petunia plants is essential to keeping them looking their best during their short stay in your garden.

You must have noticed how, over time, your fabulous hanging petunia baskets suddenly look awful, with stringy, long stems dangling limply down the side of the pot. The leaves are yellowing and the few colorful flowers hold onto the ends of the stems like sailors climbing out of the sea on ropes tossed their way. This is especially maddening when your neighbors on both sides have petunia baskets brimming with bright flowers all summer long.

Pruning petunias makes the difference. Do petunias need pruning? They absolutely do, and the difference between gorgeous hanging baskets and stringy-looking ones involves appropriate trimming of these plants.

How to Cut Back Petunias

It’s easy enough to keep your petunias attractive all summer long if you begin early with maintenance and keep at it through the life of the plant. Maintenance is especially important if you brought home a full and flowering hanging basket in late spring.

Before you begin cutting back petunia plants, take a close look at them. Notice that the plants – whether they are the Wave varieties, Super Petunias or just regular ones – only produce flowers at the very end of the stems. That means that as those stems grow longer, you’ll have flowers at the very end of bare stems.

For best results, start pruning petunias soon after you install them in your yard. Cutting back petunia plants is not hard. You need to clip a few stems every week. Start early, even if this means you must trim off stems that have attractive flowers on them. Whenever your petunia stems are eight inches long (20 cm.) or longer, begin the pruning schedule. If your plants are small when you buy them and the stems are shorter than eight inches (20 cm.), you can wait awhile to clip.

Here’s how to cut back petunias. Each week, you clip three or four stems in half, making the cuts above a node. The petunia plant will then produce two new growing tips just below each cut, and those tips will begin flowering soon. Pruning petunias regularly from the time you buy them will keep your plants gorgeous and healthy.

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Often grown as annuals, petunias are one of the most popular flowers because of their long flowering period. As with most annuals, they get leggy by midsummer, so you’ll want to prune the shoots back to about half their length. See how to plant and take care of your petunias to keep them blooming.

Pretty petunias are treated as annuals in most areas but also as tender perennials in Zones 9 to 11. The flowers come in many colors and patters, and bloom from spring until frost!

These colorful annuals can really add pop to a front lawn and often used as borders, containers, hanging baskets or even seasonal groundcover. Some even have a slight fragrance.

Height can vary from 6 inches to 18 inches. Spread can be from 18 inches to 4 feet.

Petunias are divided into different groups, mainly based on flower size:

  1. Multiflora petunias are the most durable and prolific. They have smaller, but more abundant flowers and are ideal for summer bedding or in a mixed border (because they are more tolerant to wet weather).
  2. Grandiflora petunias have very large flowers and are best grown in containers or hanging baskets (because they are more susceptible to rain damage). Theese large petunias often do not fare as well in the south because they’re prone to rot during humid, hot summers.
  3. Floribundas: Floribundas are intermediate between the grandiflora and the multiflora groups. They are free-flowering like the multiflora varieties and produce medium-sized blooms.
  4. Millifloras: Milliflora petunias are much smaller than any other petunias on the market. The flowers are only 1 to 1½ inches wide, but they are prolific and last all season!
  5. Spreading or Trailing Petunias: These are low-growing but spread as much as 3 to 4 feet. They form a beautiful, colorful groundcover because the flowers form along the entire length of each stem. They can be used in window boxes or hanging baskets.


April – Or whenever spring comes in your location.

  • When you buy in the spring, buy a slow release fertilizer to top dress the basket or container. If you plant your own basket, incorporate some of the slow release fertilizer in the soil as you plant. Follow the package directions.

May - fertilize with a water-soluble fertilizer once every two weeks.

  • Mix up the fertilizer and water the plants just like you would if you were using clear water. It normally takes a good half of gallon of water to really water a 10" wide basket or raised container.

June - as the weather starts to get warm to hot, fertilize weekly, again with a good soaking.

  • If the weather turns really hot as it sometimes does in Late June you may need to fertilize every third watering. By now the Supertunia is really growing and starting to tumble down from the basket or fill out across the flowerbed.

July - is when the cutting back occurs.

Around the 4th of July, (after your big party) get some of the slow release fertilizer that you bought in spring and re-apply across the top of the planter. By now with July's heat you should be watering at least every other day and begin to fertilize every other watering. I know it sounds like a lot, but if you want a plant to grow like an elephant and be the most it can be, you got to feed it like an elephant!

At the same time, trim back some of the longer branches just enough to bring the plant back in line with the bottom of the pot or basket. Don't remove too much at the maximum cut back 20% of the branches or 1 in five shoots. You can also just give it a general light trim. Your plant will be out of flower for a few days, but will come back stronger than ever.

August - is, hot, humid, & sometimes with monsoons. Keep up the water and fertilizing.

  • Again, if the plant starts to look straggly remove a few more branches but never more than 20% or give it a general trim as before.

September - The plants should still look good, as you start to back off the watering and the feed

  • Shape the basket with the last pruning of the season. Hopefully this will now carry you through until frost!

NOTE: For folks in the deep south – your calendar will likely start & finish earlier. For the deep south most Petunias struggle in August heat and humidity, as well as the afternoon rains, so expect petunia season to end usually in late-July or mid-August. To extend your season, move planters under protection from rains, but make sure to keep them in the sun for best flowering.


How to Prune Petunias

Are you pruning your petunias properly?

Petunias are a beautiful flower that comes in a wide range of colors (red, white, pink, purple) and types (normal and wave). It's perfect in planters, hanging baskets, and for adding a splash of color to a garden. They live best in the sun but in my experience you can plant them anywhere and they look beautiful.

The key to keeping them beautiful is proper pruning technique. This is the part that most people don't like because it's a hassle and it's too hard and they just don't know how to do it.

Most people will simply pull off the dead flower and call it good. This is not correct. The seed pod is still left behind. This is the plant's goal, to make a seed and once they accomplish that goal they no longer have a reason to flower.

So, if you remove the seed the plant has to keep flowering to make more. Not to mention that this streamlines your plant and makes it look much nicer.


Common Pests/Diseases

Petunias generally don’t have any serious issues with pests or diseases. They can be damaged by heavy winds and rain, so aim to offer them some protection from extreme weather. They also can be susceptible to fungal diseases, such as gray mold, especially in rainy climates. Opt for a variety that has a higher tolerance for moisture if you live in wet conditions. Plus, some pests that might bother them include aphids and budworm caterpillars, which feed on the stems and leaves. Often you can just hose pests off the plants with a strong blast of water. But if the infestation is severe and impeding flowering, you can use an insecticide.


Follow Up Steps to Fix Leggy Petunias

After you’ve completed your pruning steps for making your petunias fuller, things should start to look pretty great within a couple of weeks. You’ll want to keep up with your new watering schedule on an ongoing basis if your weather is really hot and dry and make sure you’re deadheading correctly at least every 3 days. When you start to see a few long, lanky stems getting out of control again, it’s time to start pruning!

If you’ve ever wondered how people are able to still have beautiful, full planters of petunias well into the fall months, this is what they do!

Have you ever dealt with leggy petunias? What are your favourite petunia tricks?


Watch the video: Ms. Smiths Greenhouse: Pruning Petunias


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