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How Deep to Plant Petunias? (All You Need to Know)

While growing any plant regardless of in the ground or in the flowering pots, it’s essential to plant the plants at a certain depth in the soil so that the rootball can get enough space to sit properly in the soil.

And the upper roots can get space to sit on the upper soil surface. Thereby, while planting petunias, probably you would like to know how deep you need to plant petunias if you aren’t aware of it. 

Therefore, keep on reading to find out the answers to your queries.

How Deep To Plant Petunias?

Whether be it in flower beds or in the flowering pots, petunias should be planted at least 8 inches to 10 inches deep inside the soil so that their rootball can get the same depth as the place where they originally were grown. It also will let the upper roots get leveled with the upper soil surface.

Just like any other flowering plants, petunias ate required to be planted at a specific depth so that there is enough room for their rootball to sit comfortably. And for petunias, the ideal depth to be planted in the soil is 8 inches to 10 inches.

It’s because when soil or pot mixing is prepared for petunias, the compost is incorporated till 8 inches to 10 inches deep so that after planting the petunia roots get all necessary nutrition from the soil.

Moreover, at this depth, the upper roots of petunias get smoothly leveled up with soil surface, thus, it’s suggested to plant petunias at 8”-10” deep in soil. 

And know that this recommended depth for growing petunias goes for any variety of petunias. So, if the most popular wave petunias are about to be planted, they should be planted at 8”-10” deep in the soil. 

However, if you are not sure about the depth, while planting seedlings or young petunia plants, plant them almost at the same depth the seedlings or young plants were born in the container or nursery. 

Also, below how deep petunia seeds should be planted in pots and petunias in flower beds have been added for your knowledge. 

Petunia Seeds In Pots:

Petunia seeds are very tiny and light that wind can blow away these seeds. So there’s no need of planting the seeds deep inside a pot.

Like most people, you can just sprinkle the petunia seeds in pot soil, or make a small hole with your fingertip and put a few seeds per hole. 

Petunia In Flower Bed:

Petunias in flower beds in the garden should be planted as deep as 8”-10” in the soil. It’s the same depth mentioned above and it’s suggested for growing any type of petunias in flower beds. 

And in case, you aren’t aware or confused, just plant the petunias in the flower beds at the same or almost at a similar depth as their container where they originally were grown. 

How Deep Should Soil Be For Petunias?

If you are growing petunias in the flower bed in the garden, you probably can’t tell how deep the soil has gone in the ground. As a result, it’s suggested that the hole where petunia plants will be transplanted should be 8 inches to 10 inches deep at least. 

So the soil should be a minimum depth of 12 inches.

But if you are about to plant petunias in a container/pot, the soil should be as deep as the pot/container’s depth, which is 12 inches. And the hole for planting petunias should be 8”-10” in the soil. 

When To Plant Petunias? 

Petunias are very tender flowering plants that absolutely can’t tolerate the harshness of the winter season, nor will be able to withstand the frost.

So if you are planning to plant your petunias outside, you must plant these tender flowering plants when the threat of cold and frost has totally passed away. 

Specifically, to say, you should plant petunias when it’s late springtime or early summer because at that time there is no cold or frost, and the petunias will get the full and bright sun to thrive fully. 

Where Should I Plant Petunias?

You should plant petunias in such a place outside where full and bright sunlight directly falls upon the ground.

It’s because petunias are an absolute lover of full sun and they do require full, direct, and bright sun to grow in their best condition, thrive healthily, and produce blossoms fully.

Thus, a spot where petunias can get 6-8 hours of direct and full sun every day is the ideal spot for planting petunias.

How Far To Plant Petunias Apart? 

Depending on the petunia type, the small, compact, and the straight petunias should be planted 15-20 cm apart, the bushy petunia with mounting habit should be planted 30 cm apart, and the trailing petunia varieties should be planted 40 cm apart. 

And if you are planting a group of 3-4 petunia seedlings, plant them 20-30 cm apart in a side-by-side manner in rows. 

How Do You Prepare The Soil For Petunias?

Here, helpful tips that would help you in preparing the soil for petunias are listed below, check them out once before you plant petunias. 

Prepare The Right Soil: 

Petunias, regardless of the variety require sandy soil to grow, thrive, and produce flowers to the fullest because sandy soil has a well-drainage system, thus, water doesn’t retain and the roots of petunias get enough moisture.

So get coarse sand flower beds to increase the drainage of the and make your garden’s soil sandy enough to plant petunias. 

Mix coarse sand in the containers as well while growing petunias.

Have A Certain pH Level In The Soil: 

Petunias prefer slightly acidic soil to thrive in their best condition, and the pH level of such soil should range between pH 6.0-pH 7.0. So the next tip for you is to test and know the pH level of your garden soil or pot mixer. 

If you already know the pH level of your soil, then either balance the pH level by adding organic matter/compost or if you don’t know take a sample of the soil and go to the local extension office. The experts will let you know. 

Mix Compost: 

To provide sufficient richness, fertility, and the required pH level, mix fertilizer/compost to the soil before you plant petunias. 

Since petunias need soil with 25% of organic matter, you should apply at least 2”-3” thick organic matter like aged manure, peat moss, or nicely rotted compost.

Then incorporate the organic matter at 8 inches to 10 inches deep into the soil by using a garden fork. This will increase the ability to hold moisture and nutrients in the soil. 

For containers, mix equal portions of peat moss and stripped pine bark along with sand to improve drainage. 

How To Plant Petunias From Seed?

Many of you prefer growing petunias from seedlings, therefore, step-by-step instructions are added here to explain you the whole process of planting petunias from seeds.  

Check The Seedlings: 

Generally, the petunia seeds take 7-10 days to germinate but until the seedlings have grown 2-3 true leaves, you can’t transplant them into containers for further growth. So check first whether the seedlings are ready to be transplanted or not. 

Get The Container Ready: 

Once petunia seedlings have 2-3 true leaves, plant them in containers but before you must get the container ready. You can either choose large containers or 3-4 inches small containers.

Fill the container with potting mix, then add some rotted compost, peat moss, or aged manure to balance out the pH level. Mix them well with the potting mix. 

Plant The Seedlings: 

Now that the potting mix is ready, for each petunia seedling dig up individual holes around the size of their original container where they grew up.

Then put seedlings one by one in their individual holes but don’t place them any deeper than their original container. After that fill each hole with the potting mix by pressing it gently. 

Provide Sunlight And Water Regularly: 

Petunia seedlings need full and direct sunlight too. So you must keep the container near a window or any other place where the seedlings will get 6 hours of bright and full sun every day.

If you can’t provide the seedlings with adequate sunlight, use fluorescent light and provide the seedlings with 12-16 hours of fluorescent light. The light should be 4-6” above the seedlings. 

Also, make sure to water the seedlings regularly but don’t make the soil too watery, just keep it moist enough. 

Feed Fertilizer: 

For better growth, petunia seedlings need fertilizer. Feed the seedlings a slow-release fertilizer or dilute a suitable fertilizer solution for petunias and apply it every 2 weeks. 

Final Thoughts

Petunias are required to be planted 8”-10” deep into the soil so that the plants’ rootballs get enough room to settle, the top roots can be leveled with the topsoil surface, and the plants can get needed nutrition and a better drainage system in the soil.