If your petunias looked spectacular in May but have slowed down—or stopped blooming altogether—don't give up on them. With a few simple care tweaks, including more frequent feeding and proper deadheading, you can keep petunias covered in flowers well into fall.
Find a Bright Spot
While petunias can tolerate partial shade, they will bloom more in full sun. About 6 to 8 hours of sun a day is ideal. That said, you should keep an eye on temperatures in the summer. If the summer heat becomes intense, move them to a shadier spot to prevent wilting flowers and sunburnt leaves.
Water Regularly
In the hot summer months, petunias need regular watering. Petunias growing in hanging baskets and containers may need water every day during periods of extreme heat, while those planted in the ground usually require less frequent watering. Water deeply whenever the top inch of soil feels dry rather than giving plants a light daily sprinkle.
Add Fertilizer
Petunias are heavy feeders because they produce flowers continuously. The University of Minnesota Extension (UME) recommends using a liquid fertilizer made for flowering plants every two weeks starting in midsummer. If your petunias are planted in the ground, fertilize every 3 weeks.
Remove Spent Blooms
As flowers fade, you can remove them to encourage new growth and keep your plantings looking fresh. You want to remove faded flowers before they have a chance to produce seed. This encourages the plant to put its energy into making new blooms instead. When deadheading, remove both the flower and the small swollen seed pod just below it.
There are some modern hybrid varieties that are “self-cleaning,” which means that the plants shed their spent flowers, so you don’t have to do it.
Trim Back Leggy Plants
By midsummer, petunias can become leggy, sparse, and produce fewer flowers. If stems become gangly, trim them back by about one-third, then water well and fertilize. New growth typically appears within a couple of weeks, producing a fuller plant and more blooms.
Know Your Petunias
With their cheerful flowers and graceful trailing vines, petunias are made for containers, window boxes, and hanging baskets. They also look great planted in the ground, where they can form billowy mounds of bright color. These plants are ideal for gardeners of any experience level because they are blissfully easy to grow. And if you give them a little extra care, they will reward you with piles of petals all summer long.
Petunias come in a dizzying array of colors and petal types, but they typically fall into four categories, according to the UME.
- Milliflora: Small plants with tiny flowers
- Multiflora: Small flowers in large amounts
- Grandiflora: Large flowers
- Spreading varieties: Plants with trailing vines that are ideal for hanging containers and large spaces, like garden beds
