Petunias are one of the most popular flowering plants in the world. Not only do they grow stunning blooms with delicate, vibrant petals, but they also give off a delightful fragrance.
On top of that, they’re incredibly easy to grow. With a little water and the right soil type, you can fill your garden with these flowers in no time.
Yet, to ensure your petunias grow properly, you’ll need to fertilize them on a stable schedule. This will ensure the plants have all the nutrients they need to stay healthy.
At this point, you may wonder, what’s the best fertilizer for petunias? If that’s the case, I can help.
In this article, I’ll walk you through everything you need to know about petunia fertilization. I’ll cover the ideal type of plant food to use and how often you should be adding it.
What Are Petunia Fertilizer Requirements?
Before you start sprinkling fertilizers on your petunias, it’s crucial that you understand the plants’ requirements. That way, you can ensure that the flowers stay in bloom for as long as possible.
Petunias are perennial plants that belong to the Nightshade family. They have five fused petals that combine to create a unique funnel-shaped flower.
On top of that, the blooms give off an exceptionally sweet aroma that can fill up any space.
Moving on, most petunia varieties have an incredibly rapid growth rate. The seedlings can bloom into flowers in as little as 12 weeks.
Plus, each petunia plant can produce many blooms per year. This means that with just a few seeds, you can grow a massive bed of these stunning florae.
However, to keep up with the rapid growth rate and abundant blooms, the plants need a lot of nutrients.
That’s when fertilizers come into play. You should feed your petunias on a regular basis to ensure they have all the minerals and vitamins they need to maintain healthy blooms.
What Type of Fertilizer Is Best for Petunias?
Most plants need a combination of a few different nutrients to maintain a steady growth rate. These include nitrogen, phosphorus, and potassium.
Nitrogen will act as a building block for chlorophyll, which will allow your petunias to carry out photosynthesis. Moving on, phosphorus helps minerals travel across different parts of the plants to ensure that the flowers can stay in bloom for a long while.
Finally, potassium aids with root growth and improves drought resistance.
As you can tell, all three of these nutrients are exceptionally crucial for the health of your petunias. So, you’ll need a fertilizer that contains some amount of each of these minerals.
Since nitrogen is soluble in water, it can wash out of your soil when excess moisture is present. Luckily, the same isn’t true for the other two minerals.
Phosphorus and potassium are relatively insoluble in water, so your soil should have a constant concentration of these nutrients.
That means your fertilizer should have more nitrogen than the other two minerals. Because of that, a 3-2-1 NPK ratio fertilizer should be ideal for petunia.
This plant food contains three parts nitrogen, two parts phosphorus, and one part potassium.
Plus, you can also use an 8-8-8 fertilizer in a pinch.
Lastly, it’s best to use a liquid fertilizer made specifically for flowering plants rather than a solid one. That way, your soil will be able to absorb the minerals faster to keep up with the growing demands of your petunias.
When Is the Best Time to Fertilize Petunias?
Petunias are delicate flowers that can’t tolerate low temperatures. Because of that, it’s a good idea to wait until spring to plant your seeds.
As soon as the seedlings are in your soil, you can sprinkle a little fertilizer on top to help kick-start the growing process.
The initial feeding will set the stage for the entire growing season. For that reason, it’s important that you ensure your growing medium contains all the nutrients petunias need to stay healthy.
You can also fertilize your plants in the summer to ensure the blooms stay vibrant and strong throughout the warm season.
Yet, as the temperature begins to drop with the arrival of fall, you can pull back on the fertilization. As I mentioned, petunias won’t grow well in the cold.
So, adding plant food during winter and fall won’t do the florae much good.
How Often Should You Fertilize Petunias?
As a general rule, petunias will need a fertilizer top-off every two to three weeks. This will guarantee that you keep up with your plant’s nutritional needs.
Yet, the exact schedule can change based on where you live, the type of petunias you’re growing, and where you plant your flowers.
If you live in an area with high humidity levels, then you’ll need to fertilize your petunias more often than twice a month.
A good rule of thumb is to add plant food about once a week.
That’s because the excess moisture in the air will affect the soil composition and wash away some of the minerals from the growing medium.
Moving on, some petunia varieties grow faster than others. So, you’ll need to supply them with plant food more often to support the rapid growth rate.
Lastly, if you’re growing petunias in pots, it’s best to feed them every two weeks. As for petunias in garden beds, they’ll need more frequent fertilization.
In that case, adding plant food once a week should do the trick.
However, this fertilization schedule isn’t a substitute for healthy soil. Sprinkling plant food will only supply your petunias with a few of the nutrients they need to grow.
So, be sure to add mulch, compost, and manures to fortify your soil and build an organic growing medium.
How to Fertilize Petunias
Each fertilizer is a little different. So, depending on the type you use, the fertilization steps will be slightly different.
For that reason, it’s best to read the instructions that come on the back of your plant food. They should be able to give you detailed directions on how to fortify your soil.
Do Petunias Like Acidic Soil?
Yes, petunias prefer to grow in a slightly acidic environment. Because of that, to ensure your plants have the best chance of thriving, you’ll need to keep an eye on the soil pH.
Do Petunias Like Coffee Grounds?
While most people aren’t aware of the fact, coffee is an excellent source of nitrogen. The grounds contain a healthy dose of the nutrient, which means they can help fertilize your soil.
Since petunias rely heavily on nitrogen, sprinkling some coffee grounds on your growing medium can do wonders for your flowers.
Plus, as I mentioned, petunias like growing in an acidic environment. Luckily, coffee grounds are slightly acidic and can help you maintain your soil pH.
Are Eggshells Good for Petunias?
Even though egg shells contain minerals, they’re not great for your petunias. That’s because the shells have a high concentration of calcium.
This mineral is slightly basic, which means it can alter the soil pH and turn it more alkaline. Sadly, that’ll stop your plants from developing properly.
Can You Over-Fertilize Petunias?
If you add fertilizer to petunias too frequently, it can lead to a whole host of problems. That includes yellowed leaves, which will affect your plant’s ability to carry out photosynthesis and produce energy.
Other than that, the petals can start to wilt due to a mineral imbalance. Finally, the extra nutrients will cause the roots to soften.
Sadly, this will make it challenging for the plants to stay anchored in the ground. Plus, it’ll affect their ability to absorb water and minerals from the soil.
For that reason, it’s best to avoid fertilizing your petunias more than once a week.
What Type of Soil Is Best for Petunias?
Petunias like to grow in a well-drained growing medium that contains plenty of nutrients. So, you’ll need to use deep, loamy soil to ensure your plants have the support they need to bloom.
Final Thoughts
Petunias require nitrogen, phosphorus, and potassium to maintain a healthy growth rate. So, when looking for the best fertilizer for petunias, you need to ensure it contains all three minerals.
A 3-2-1 NPK fertilizer should be ideal, but you can also use 8-8-8 plant food in a pinch.
Besides that, you want to feed your petunias about once every two or three weeks. Yet, if you’re growing the flowers in a garden bed, you may want to increase that to once a week.
Growing up with a mom who filled her home (inside and out) with all sorts of plants, Lisa got her start in gardening at a young age. Living now on her own with a home and yard full of plants (including an indoor greenhouse), she shares all the gardening tips she’s gained over the years.