Updated at: 22-04-2022 - By: Sienna Lewis

When it comes to growing petunias in a greenhouse, passion and dedication are required. With their wide range of colors, styles, and sizes, well-tended petunias have changed the game when it comes to gardening outputs.

Why are short, vegetative crops so popular in today’s markets? What you need is a well-thought-out program and product recommendations to follow.

The Greenhouse Petunia: Overview

In the greenhouse, petunias are given a new home. Petunia is a genus of 20 flowering plant species native to South American areas, and its name has a fascinating etymology. Its name originates from “petun,” which means “tobacco” in French.

How To Prepare A Greenhouse Petunia For Planting - Krostrade

The trumpet-shaped flowers of this plant make it ideal for window boxes and flowerbeds during the summer months. Sessile leaves and oval-shaped leaves characterize the majority of these species. They also have funnel-shaped flowers with five petals that are either fully or partially united, as well as five green sepals.

About Petunias

Even though petunias are commonly cultivated as one-year annuals, zones 9–11 are suitable for growing them year after year as sensitive perennials. The flowers bloom from spring till frost, and they come in a variety of hues and patterns.

It is common to see these brightly colored annuals utilized in borders, pots, hanging baskets, and even as a seasonal ground cover in front yards. Some of them even have a faint scent to them.

Six to 18 inches in height is possible. A spread of 18 inches to 4 feet is possible.

Petunias are classified according to the size of their flowers, which determines the majority of the classifications.

  1. They’re the most long-lasting and prolific of all the petunias. For summer bedding or a mixed border, they have smaller, but more numerous, flowers and are more tolerant of damp conditions.
  2. Grandiflora petunias have very large flowers and are best grown in containers or hanging baskets (because they are more susceptible to rain damage). Because of the humid, hot summers, these huge petunias generally fail to thrive in the south.
  3. Grandifloras and multifloras: Floribundas fall somewhere in the middle of the two groupings. Like the multiflora types, they produce medium-sized blooms that are free-flowering.
  4. These petunias, known as millifloras, are the tiniest you’ll find. Prolific and lasting all season long, the blossoms are barely 1 to 112 inches wide.
  5. Low-growing spreading or trailing petunias can spread up to three or four feet. Because the flowers grow all the way down the stem, they make a stunning groundcover. Window boxes and hanging baskets can be used with them.

How To Grow Petunias

When it comes to care for your petunias, there are a number of things you may need to take.

Planting petunias

In order to thrive in the garden, petunias need to be placed in direct sunlight, otherwise, they will grow lanky. Their adaptability and ability to grow in a variety of soils have made these herbs a favorite of cooks and gardeners alike. Petunias require well-drained soil, so keep that in mind while planting.

If you choose, petunias can be grown from seed, but it may be more convenient to start with petunia transplants instead. If you’re going to grow plants from seeds, start them indoors about ten weeks before transplanting them to the garden. Because their seeds are so tiny, they need a lot of light to germinate.

If you don’t water them regularly, you won’t be able to transplant them outside until they have three leaves. Buying young plants from the petunia nursery, which often sells the herbs in flats, is highly recommended. Compact and short plants, not lanky or flowering are better since they tend to establish themselves more quickly.

You can also plant petunias if the last spring has had frost in a place that isn’t exposed to strong winds. Make sure to give it plenty of water. The ideal spacing for petunias is one foot apart. You’ll need your soilless mixture if you’re going to plant these in a container.

Choosing and Preparing the Planting Site

  • Petunias will turn spindly if not given full sun. In the shadow, they are less likely to bloom.
  • They may thrive in a wide range of soil conditions, as long as the soil is well-drained and does not become stagnant.
  • For optimal growth, soil should have a reasonable level of fertility. Before you plant, improve the soil by adding compost.

Caring for petunias

So that you don’t have to keep watering petunias all the time, you need to make sure they get enough heat. Unless your region is experiencing a drought, weekly watering of petunias is sufficient.

The general rule of thumb is that petunias that spread and those that are grown in pots require more watering. You must also be able to fertilize petunias on a monthly basis with the correct fertilizer to ensure that they develop and bloom properly.

How To Prepare A Greenhouse Petunia For Planting. 5 Easy Steps - Krostrade

Due to a lack of foliage, a plant may develop flowers from the tips of its stems, which are lanky in the summer. Begin by snipping the petunia shoots back to about half their original length. The more you do this, the more flowers and branches you will get.

Water and fertilize the petunias after you’ve finished pruning. This will encourage the growth of new flowers and plants. These plants may appear ragged at first, but as time passes, you’ll notice more blossoms.

In colder climates, elder petunia plants are clipped severely to promote growth, but the remaining leaves are left intact. Compost piles can be used to recycle grass clippings as well. As a result of this, it is time to learn how to grow petunias in a greenhouse.


  • ‘Carpet Series’ is a huge hit. They’re little, early bloomers, with 112- to 2-inch blooms, and a wide range of colors; they’re perfect for covering large areas.
  • Primetime series remain small and uniform, covered with 214-inch flowers. Primetime series.
  • “Heavenly Lavender” is a 3-inch double lavender blue with 12- to 14-inch plants and an early bloom time.


  • A purple petunia with dark veins, ‘Sugar Daddy’ (Petunia Daddy Series) stands out.
  • Because of its rose-pink blooms with white centers, ‘Rose Star’ (Petunia Ultra Series) seems striped.


  • Petunias in the ‘Celebrity’ series are compact and tolerant of rain. 2 to 2 and a half to three-inch-wide blooms cover the plant.
  • This collection of petunias features large, 3-inch flowers in a variety of hues, including solids and veins. Flowering lasts till the first frost. After a rainstorm, they recover quickly.
  • Petunia ‘Double Madness’ blooms all summer long with large, 3-inch flowers and is compact and floriferous. ‘Double Madness’ petunias, like their single-flower siblings, bounce back quickly after a downpour.


  • “Fantasy” grows in tidy mounds.

Trailing Petunias

  • ‘Purple Wave’ was the first spreading petunia cultivar to be developed. It has big, rose-purple blooms. Summer heat, dryness, and rain will not harm it. ‘Purple Wave’ is still just about 4 millimeters high.
  • Wave series petunias can be found in a wide range of hues. Compared to the original, most aren’t quite as ground-hugging. It is hardy in all climates and disease-resistant, as well as producing a lot of flowers.

How Do You Prepare A Greenhouse For Planting?

To grow a greenhouse petunia successfully, you need to have a firm grasp of the fundamentals. Planting your petunias is just as important as preparing your greenhouse for the task. Before planting the seedling, clear the greenhouse of any debris. The removal of yellow leaves and dead organisms is a must. The second step is to thoroughly clean the greenhouse. Think about cleaning the stairwells and shelves as well as the frame.

After that, it’s time to get the soil in the greenhouse ready for planting. Changing the soil may be necessary depending on the method used to develop the plants. There are a number of tasks that need to be completed next, such as checking the watering system, diagnosing any major problems, cleaning the greenhouse using the catchment system and inspecting the water buds.

As a last step, you should think about installing power and heating in your greenhouse. When you follow these guidelines, everything will be fine and dandy.

How Do You Prepare Soil For Petunias?

Soil preparation is an essential part of preparing the greenhouse. Petunias require soil that contains at least 25% organic matter in order to thrive. In order to avoid rotting, avoid using soil that is excessively dense.

Make sure the soil is loose and lovely by digging into it thoroughly. Before planting these petunias, the soil needs to be fertilized. Make careful to add organic matter to the soil if you’re doing this in the garden. Three inches of thickness is a good rule of thumb.

Do Petunias Like Coffee Grounds?

Petunias’ connection to coffee grounds is one of the most intriguing aspects of the plant. You can get free fertilizer by dumping used coffee grounds on petunias, thanks to gardeners who do this. To begin, add coffee grounds to the coffee maker and utilize the solution in various containers throughout the day. When planting a petunia in a greenhouse, follow these instructions.


Question 1: Is it possible in may to sow petunias immediately in the open?

Simple garden Petunia types can be seeded throughout the year, not just in the spring; in fact, the plant reproduces flawlessly by self-seeding. Modern hybrids, especially at the seedling stage, are more erratic and demanding of the conditions of confinement, thus such a focus will be impossible to maintain.

To see if it’s possible to raise pampered hybrids in such an open environment, try it out:

  • minimum 1-2 millimeters below the surface of the sowing medium;
  • temperature should be kept between +23…+25°C and +18…+20°C, and +15°C at night, till the development of shoots occurs.
  • persistent moisture in the ground. When left to dry out, Petunia seedlings can perish in just a few hours. In order to avoid all types of rot, waterlogging is not a desired condition. What happens if the raindrops charge and the first condition is met?

Even if you’ve spent a lot of time and effort cultivating your petunias in the open ground, estimate how long it will take them to reward you with flowers if the first bloom comes 55-80 days (depending on the species, growing circumstances, severity of pinching, fertilizing, etc.) after sowing.

Question 2: when it is necessary to sow Petunia that it blossomed in April-may?

In order to answer this question definitively, it is necessary to take into account a wide range of factors (lighting, temperature, fertilization, etc.) that affect the growth of seedlings.

How to Grow Petunias - BBC Gardeners World Magazine

Petunia seed tests, I believe, are the best bet. Details of the growing conditions (which can be compared to their own) as well as sowing and flowering dates for various hybrids are provided. Petunias are not grown in their first year, so you can read the comments and learn a lot from gardeners who are not participating in the study.

Question 3: how long should we wait for shoots?

When the shoots hadn’t appeared in two weeks, I realized that it made no sense to wait any longer. Even if sprouts show 30 days after sowing, they are of no use because the plants will grow and develop slowly, and they will not be able to blossom as well.

If a virus is discovered in a flower garden, “strong healthy plants” will be able to reject the enemy, and “those that are not very” will be included in his victims. They are hardly able to maintain themselves in the face of the enemy’s onslaught.

Question 4: how to slow down the growth of seedlings?

The simplest method is to use large-capacity transshipment. For those who have access to a greenhouse or a greenhouse greenhouse, the second option is easy but not universally available: to grow seedlings in an environment where the temperature does not rise over +10…+15°C.

Using growth regulators is a third method that I don’t like, but it’s necessary when you can’t avoid chemistry.

Question 5: quickly dries up the soil in street pots with petunias. What to do?

The soil should be amended with hydrogel, perlite, or vermiculite before planting. Pull over the grid of the flowerpots if you can.

My own first-hand knowledge tells me that during the summer months, none of the previously mentioned options — not even the escape – are available. Despite the fact that potted soil does not fracture in a single day, it must be watered consistently in the morning and at night. As if someone forgot to turn off a gigantic hair drier, the temperature in the shade rises to more than 40°C and the wind is bursting with heat all day. What if the nighttime temperature doesn’t go below +28°C for weeks? All these minor tricks, of course, will work in places with lower temperatures.

Question 6: what and when to feed Petunia?

As soon as the second true leaf appears, 2 weeks after plucking in a separate container, petunias begin self-fertilizing.

NPK or complex fertilizers will be used for the first feedings. Nitrogen fertilizer must be used to increase the green mass prior to the development of Petunia buds. When the flowers begin to open, switch to phosphorus-potassium fertilizers.

Question 7:how to pinch petunias?

Those who dislike this technique (sorry for the bloom) should know that modern shrub kinds in pinching do not require our participation and will reclaim overgrown side shoots on their own. Baskets designed to promote the development of long stems may be of some use; as long as they are not rushed, that is. I couldn’t find any universal rigorous laws governing petunias, and gardeners’ perspectives on this matter vary widely.. However, the majority of experts still advise removing the top 5-6 sheets of the shot.

Question 8: why do petunias turn yellow leaves?

Chlorosis is most likely the outcome of the plant’s inability to absorb iron. Overflow (too much moisture in the soil prevents the roots from adequately absorbing nutrients) or irrigation with harsh water may be to blame (calcium accumulates quickly in the soil, it latches).

The heat could be making Petunia uneasy, or she could simply be starving.

Question 9: why did Petunia stop blooming?

Not cutting fading stems is most likely because the plant tends to tie the seeds (even hybrids try, but they don’t succeed) to the detriment of flowering, which is the most likely explanation.

Deficiency of nutrients, such as depleted soil resources or insufficient fertilization, could also be the cause. Alternatively, your Petunia may be suffering from a lack of light: living in the shadows will have a negative impact on flowering.

Question 10: why does Petunia stretch out and not Bush?

Some Basket Petunias get side shoots, therefore it’s possible this is a genetic trait. Or the plant is in desperate need of light. ‘

Question 11: how to propagate Petunia cuttings?

The cuttings can be rooted in the ground:

  • from the mother plant, cuttings are taken
  • The bottom leaves are totally removed, while the top ones are chopped in half or thirds so that the cuttings can take root more easily. The stem is powdered with a root development stimulant and planted in a greenhouse after being dipped in water initially.
  • After 7-9 days, root cuttings are gradually acclimatized to the new circumstances of detention by means of ventilation.

Even cuttings of petunias have an excellent shape and are growing roots in a solution of rooting stimulant.

The answer to your query has been found. Ask in the comments if you can’t find it!