Wave petunias are marathon bloomers – from spring to fall – and how many flowers do they produce? It’s insane! Their blooms literally cover the whole plant, with their amazingly bright colors, however… They usually start off with a breathtaking display, but come June… You start seeing dry stems, fewer blossoms, and, overall, you get the point: they are feeling the fatigue. But does it need to be like this? The answer is no!
Wave petunias really need some simple care to keep you gazing at their massive floral performance from spring to fall, and here is all you need to do!
1: Size Matters! Choose the Right Pot
Put very simply, if the pot is small, your wave petunia’s roots won’t have space to grow. The consequence? It will give you a wonderful floral spectacle at first, but then it will stop. So, how to find out if its container is too small?
Your wave petunia will stop growing and literally produce fewer buds and flowers. If it does this by summertime, you should repot it.
But how big should a pot be? For a group of 3 wave petunia plants (a classic) the container should be 10 to 12 inches in diameter (25 to 30 cm). For a single one, 8 inches will suffice. However, work out the math, and you’ll see why it’s convenient to grow a few together.
2: Heat and Cold: Two Big Risks for Wave Petunias
Just imagine being a wave petunia… You have to blossom from spring (when it gets cold) through summer (when you sweat all day) and up until frost! Not an easy task…
So, when wave petunias start blooming, you should protect them from extreme cold, especially at night. You can wrap the container, that will usually do the trick, or move them somewhere warmer at night. This is when the thermometer drops below 55°F (13°C) at night. While they can tolerate temperatures as low as 35°C (2°C), this is not ideal for blooms.
Similarly, when temperatures start steadily passing the 80°F mark (27°C) during the day, they may feel the heat and their floral display will flag. In this case, cool your wave petunias at peak time, shading them, or taking them somewhere fresh. And remember that frequent watering will cool your plants as well.
Talking about which…
3: Quench Your Wave Petunias’ Thirst – But Don’t Drown Them!
Watering wave petunias is maybe one of the most difficult things to do; and if you get it wrong, they will flower less, or not at all. This is because there are two variables: the season and where they grow!
So, let’s start with wave petunias in soil, keeping in mind rainfalls and the season, you should water them every 7 to 10 days. Just check that the soil is still moist 2 inches (5.0 cm) under the surface. Feel free to irrigate them more often during a heatwave though.
On the other hand, potted wave petunias require more frequent watering. Check that the top 2 inches (5.0cm) are dry and irrigate them. This could be as often as daily or even twice a day when the weather is really hot, and much less often in spring and fall.
By the way, wave petunias do better if you water them in the morning. I know, the rule is to water your plants in the evening – but there’s always an exception…
4: Fertilize Your Wave Petunias Regularly
Can you imagine how hungry your wave petunias get in order to produce all those flowers? For this reason, you need to fertilize them really often, every 10 to 14 days!
Use a fast-release liquid fertilizer, preferably organic, and I know, you read online that it should be balanced. No! If you do, your wave petunias will produce lots of stems and fewer blossoms. The University of Massachusetts, instead, suggests an NPK of 15-30-50 or 10-30-20. And I think we can trust them…
5: Give Your Wave Petunias Enough Sunlight
Wave petunias are full Sun lovers, and you should respect this preference, or they won’t blossom as profusely… Actually, they like a lot of light…
For full Sun, we mean more than 6 hours of bright light a day, but wave petunias do best when they get more than 8 hours of sunlight.
If you grow your wave petunias in hanging baskets, I think the ideal exposure is east, followed by south, certainly not north, especially in colder countries.
6: Mulch Your Wave Petunias
Especially if you grow your wave petunias in your garden, you should mulch them, but also in containers it will help.
Lay 1 to 2 inches of good-looking mulch (2.5 to 5.0 cm), like wood bark, and this will keep the soil humid and fertile. What’s more, because wave petunias are trailing plants, it will protect the flowers and stems from infections they can get from the ground, especially when it gets wet.
7: Deadhead Your Wave Petunias’ Blossoms
To start with dried up and wilted blossoms look bad, but there is another reason why you must deadhead your wave petunias’ spent flowers: if they go to seed, they will invest most of their energy into reproducing, to the detriment of blooms!
You can snip them off with your fingers, but they are a bit softy and – honestly – unpleasant to the touch… So, I prefer a pair of small scissors, which you must always sterilize for every plant. Alcohol is perfect.
8: Prune Your wave Petunias
If you see that some stems are becoming tired, too dry, and they are producing few flowers, prune them off. You can do this at any time with wave petunias, and it will encourage them to produce more blossoms on the other stems. However, this operation will get more frequent and useful as the season progresses, especially in fall.
Use a sharp and sterile pair of scissors,so you get a neat and sharp snip, and you won’t spread any germs or fungi.
Now Your Wave Petunias Will Amaze You with Their Blooms from Spring to Frost
So, here we go: 8 tips to keep your wave petunias blooming like mad from spring to frost! Just follow them and they will amaze you with their overwhelming floral spectacle!
Written By
Amber Noyes
Amber Noyes was born and raised in a suburban California town, San Mateo. She holds a master’s degree in horticulture from the University of California as well as a BS in Biology from the University of San Francisco. With experience working on an organic farm, water conservation research, farmers’ markets, and plant nursery, she understands what makes plants thrive and how we can better understand the connection between microclimate and plant health. When she’s not on the land, Amber loves informing people of new ideas/things related to gardening, especially organic gardening, houseplants, and growing plants in a small space.