Updated at: 19-10-2022 - By: Sienna Lewis

It’s important to know the ideal greenhouse temperature for growing petunias. Since they differ for each stage of growth, they aren’t immediately apparent.

According to various expansions, however, petunia planting, establishment, and development information is freely shared in the nursery.

As long as the plants are in healthy conditions, the nursery’s ability to grow plants will be evident. The temperature in the nursery is an important component to keep an eye on when cultivating petunias.

Petunias grow best at what temperature in a greenhouse? Continue reading to find out more!

Why Grow Petunias?

Petunias are quite easy to raise from seed, but professionally prepared seedlings are even easier. Petunias look great everywhere, especially now that the sun is shining.

In front of a blooming border, near an entryway or a pool, or on a patio, the developing varieties are ideal candidates for planting.

Place petunias between the branches of evergreen trees to provide color. Make use of petunias like ‘Wave,’ which grow as groundcovers. Petunias are popular because they attract gorgeous moths at night, so many people plant them near a window or porch where they can admire the blossoms and their guests.

Optimal Temperatures In A Greenhouse For Petunias - Krostrade

Temperature Range For Growing Petunias

Underneath are diverse temperatures for planting, establishing, and developing petunias. Depending on your growing zone, you may need to make adjustments to the nursery in order to keep it running smoothly.

Petunias can thrive in a variety of climates, from the chilly north to the sweltering south. Maintaining the nursery in these conditions and making changes in accordance with your growing zone is a necessary.

Establishing or using cuttings has the advantage that the plants you produce will be comparable to the initial and sprout prior to the original plant.

The Optimal Temperature For Growing Petunias

Even though petunias require little care, they may thrive in temperatures as low as 32 degrees Fahrenheit. If you live in a location that experiences extremes of temperature, you must take precautions to protect your plants from the harsh elements.

Petunias can withstand extreme heat, however in warmer temperatures, expanded water evaporates. Deliver additional water to your petunias in the summer heat. The soil should feel somewhat damp to the touch, but not soggy or sloppy.

Around 30 degrees Fahrenheit is the melting point for most petunias. For growing petunias, what are the ideal greenhouse temperatures? Petunias thrive in areas where the temperature is above 86 degrees Fahrenheit for at least 210 days of the year. That’s society’s most important task for coping with the effects of climate change.

Ideal Temperature In Day And Night

Consider the day and night temperatures when growing petunias in the nursery. Keeping your plants in a healthy environment is critical.

Temperatures should range from 64 to 75 degrees Fahrenheit during the day and 55 to 64 degrees Fahrenheit at night. At 95 degrees Fahrenheit, petunias have a hard time.

Make sure the temperature in your greenhouse does not fluctuate so that you do not disrupt your plants in any way.

Temperature And Plant’s Growth

Petunias’ height, blooming time, and sidelong branching are all influenced by the weather.

At temperatures between 50 and 77 degrees Fahrenheit, taller plants race to blossom and shorten their side branches. Experts recommend 63°F for ten days for transplanting fair-skinned petunias.

Things To Remember In Growing Petunias

Bury up to your petunias and transplant them in indoor pots to prevent them from wilting in the cold. Furthermore, if you live in an area with a harsh climate, you may be able to cover your flowers with one of the warmed arches sold by some plant stores.

Petunias can tolerate hot weather, so they don’t require as much water. When it comes to watering your plants, once a week should plenty (unless there are drawn-out periods of a dry spell in your region). Water deeply but sparingly to avoid encouraging shallow roots.

Why Temperature Is Important?

The plant’s digesting system is greatly influenced by temperature, which is one of the most common environmental factors. Considering that plants are attached to the stem, their survival depends on resistance reactions’ proficient actuation to warm push.

The most obvious effect of high temperatures on plant development is the reduction in the efficiency of photosynthesis. Using carbon dioxide as a source of oxygen and respiration, plants make carbon dioxide by consuming oxygen.

Temperature affects plants in a variety of ways, depending on factors such as the amount of light they receive, the amount of water they need, and the distance they are from rocks.

Photosynthesis, transpiration, breath, germination, and flowering are all influenced greatly by temperature. Photosynthesis, transpiration, and breath all increase in response to an increase in temperature.

Temperature affects the transition from vegetative (verdant) to regenerative (blooming) development when paired with day length. Temperature can either hasten or slow this change, depending on the situation and the plant in question.

What Are The Optimal Temperatures In A Greenhouse For Growing Petunias: Gardener’s Guide

Planting, rooted, and growing petunias can be done at any one of the following temperatures. It is imperative that you maintain the greenhouse in these circumstances and adjust to your growth zone. Zones 10 to 11 are recommended for these blooms, according to the Missouri Botanical Garden, so be sure to check the classification for your area before ordering.

Optimal temperatures for planting petunias

You can start your petunia seeds in pots, but you must keep the temperature between 75 and 80 degrees Fahrenheit for the seeds to germinate. Direct sunlight and temperatures above 90 degrees Fahrenheit can impede germination of seeds. Temperatures should remain between 60 and 65 degrees Fahrenheit for 7 to 10 days after the seeds have sprouted.

Petunias can be grown well from seed in a greenhouse, but for transplants, outdoor planting is preferable. If you’re moving petunias from the greenhouse to the garden, what’s the best temperature for them? To avoid frost damage, the University of Minnesota Extension recommends waiting until the soil temperature reaches 60°F.

Also, remember to lower the night temperatures to 63 to 65°F in order to get the plants ready for transplant. Utah State University found that keeping the growing conditions in the greenhouse between 65°F and 75°F, and in particular 70°F and 72°F, is essential for effective seed germination. After five days, you can also keep the temperature between 75 and 78 degrees Fahrenheit in the greenhouses at Auburn University, where petunias are grown.

Use water at 70°F for greenhouse irrigation and mist.

Optimal temperatures for rooting petunias

Petunias can be grown from seed or from rooted cuttings, according on personal preference. Root the plants for 2 to 3 weeks at 64 to 75°F in this approach. Rooting or taking cuttings means that the plants you produce will be comparable to the original and blossom earlier than if you were to grow them from seed.

What Are The Optimal Temperatures In A Greenhouse For Growing Petunias - Krostrade

Optimal temperatures for growing petunias

Keep track of the day and night temperatures when caring for petunias in the greenhouse. Temperatures should range between 64°F and 75°F during the day and 55°F to 64°F at night. However, in some situations, petunias can withstand temperatures as high as 95°F.

The height of petunia plants, the time they flower, and the number of branches they produce are all regulated by temperature. Temperatures above 77°F can cause plants to grow taller, blossom earlier, and have fewer lateral branches. Experts recommend 63°F for 10 days after transplanting petunias.

Other Greenhouse Requirements For Growing Petunias

Petunias in the greenhouse require specific conditions, such as temperature and humidity, in order to thrive. Remember to utilize a pH range of 6.0 to 7.0 and a light, well-drained soil. To help petunias transition from greenhouse to outdoor beds, place them in a shaded area.

Every seven days, water the petunias by up to 2 inches. Growth and blooming can also be aided by a monthly application of a well-balanced fertilizer. Do not completely remove all of the leaves from your petunias if they have stopped flowering.

Flowering can be aided by using a liquid fertilizer and enough of water. Double petunias and those with huge blooms necessitate the removal of old and dying flowers for deadheading purposes. Cultivars with smaller flowers are more likely to take care of this on their own.

Petunias are notoriously difficult to grow. There are a few drawbacks to this flower, like aphids and snails, but it’s a good thing that it has these troubles. Petal blight and other diseases can be addressed with proper watering and humidity control.

What Is The Best Petunia For Greenhouse?

For horticulture, petunias are most known for their Grandiflora singles, Multiflora singles, as well as their double blossom varieties. Many cultivars of Grandiflora offer a broad variety of colors and sizes; yet, smaller Multiflora can endure harsh environments.

Optimum Temperature

When the temperature of a plant drops, there is a point at which the plant’s growth and development halts.’ The basal temperature varies greatly among plants and is referred to as such. A plant’s growth rate increases as the temperature rises above the base temperature, reaching a point when it can no longer grow faster. Temperatures in this range are ideal for most plant species, but they might vary considerably among them. In general, plants that originate in warmer climates have a higher optimal temperature than those that originate in cooler climates. The pace of plant growth reduces when the temperature is above the optimum. For this reason, it’s difficult to raise diverse plants with various heat requirements in the same greenhouse: each species’ optimal temperature is different. When one crop needs a certain temperature, another may not. Some considerations to keep in mind when utilizing less-than-optimal temperature regimes for spring crops are outlined below.

Seed Germination

Slower germination, less germination, and less homogeneity are all consequences of seed germination at too low a temperature. When germination is taking place, the ideal temperature for many crops is 72 to 76 degrees Fahrenheit. The majority of plants can survive temperatures that are below ideal after they have become established. You cannot cut corners on heat when it comes to seed germination.


Reduced greenhouse temperatures will lengthen the time it takes to produce and bloom. As a result, the number of crops that may be grown in a given area during the spring season is reduced. There is a possibility that more money will be spent heating crops because they are in the greenhouse longer.

Flowering time increased when temperatures fell, according to research from the University of Minnesota. The precise number of days it took for a plant to blossom depended on the type of crop being cultivated. ‘Super Elfin Lipstick’ impatiens, for example, increased flowering by 18 days if the temperature was lowered by 7°F. ‘Purple Wave’ petunias delayed blossoming by 33 days as a result of the same temperature drop. Because of this, the flowering of ‘Purple Wave’ petunia was delayed by about 3 days for every 1°F drop in temperature. Listed here are a few:

Plant Quality

Some crops may actually benefit from lower temperatures, despite longer production times. Plants’ branching, blossom size, and flower count generally increase when cultivated chilly. When the temperature dropped from 77°F to 59°F, a fuchsia named “Dollar Princess” had more lateral branching, more blooms, and larger blossoms, according to a University of Minnesota study. New Guinea impatiens, on the other hand, thrive at warmer temps. New Guinea impatiens blossoming was nearly wiped off when the temperature was lowered from 77 to 59 degrees Fahrenheit in a research.

Water uptake and Nutrition

The uptake of water and nutrients is slowed by the use of cold media. When it’s cold outside, plants, benches, and floors retain moisture longer between waterings. Foliar illnesses like Botrytis become more likely when humidity and condensation rise.

Crops should be monitored carefully to establish irrigation requirements to avoid complications. Having a colder climate means less water is needed. If possible, set the watering timer to begin at 10 a.m. and end at noon. The growing media will become even colder if water is applied too early in the day. This is crucial for growers who rely on cold water.

This includes monitoring the EC and pH and adjusting fertilizer concentrations as necessary. As a result of less frequent irrigation, plants are also fertilized less frequently.

Pest Management

Ventilation and heating can help prevent Botrytis and other foliar diseases by lowering relative humidity levels. The greenhouse will have less condensation if HAF fans are used to circulate the air.

It is possible that Botrytis and Powdery Mildew preventative fungicide applications are required in a colder greenhouse.

Root rots produced by Pythium, Rhizoctonia, and Thielaviopsis are more likely to occur in cool media. Maintain regular root checks and spray fungicides when necessary. It will take longer for fungicides to take effect in cool media. Depending on the application, it may take longer to notice benefits or the application may not be as effective.

During the early stages of the crop cycle, pests and mites may have a shorter life cycle due to the lower temperatures. However, aphids, thrips, mites, and whiteflies may arise out of nowhere when the weather warms up in the spring. Early in the production cycle, keep an eye on crops and keep an eye on them throughout the growth season.

Plant Height

Plant growth is slowed by lower than ideal temperatures, which affects both timing and size. The nighttime temperature is likely to be reduced in order to grow at a lower temperature than is ideal. Stem elongation is affected by the temperature differential between day and night. Your crop will grow taller if the temperature difference between day and night is large. That means that plants will grow taller if the nighttime temperature is lower and the daytime temperature is higher.

Tips for Growing Cooler

Plant species should be categorised into warm and cold crops based on their temperature requirements when considering lowering greenhouse temperatures this spring.

A few warm-weather crops cannot be cultivated at temperatures below their optimum (65-68F nights). Alternanthera, New Guinea impatiens, lantana, vinca, celosia, cleome, coleus, cosmos, gomphrena, ipomoea, melampodium, portulaca, and sunflowers are among the many plants that can be grown in a container.

Cool-season crops include alyssum, alyssum dianthus and pansies as well as osteospermum and osteospermum. The quality of these crops is unaffected by less-than-optimal conditions, but the time it takes to produce them is longer than if they were grown at optimal temperatures.

Plants that have developed a strong root system are better able to withstand the drop in temperature. Root systems can be created quickly if you start growing on at the right temperature. The temperature can be adjusted once the roots have established themselves and the plants have begun to expand up (2-3 weeks).

Plants should not be grown in pots placed directly on the ground in order to maximize use of greenhouse heat. Air temperatures can be 10-20 degrees Fahrenheit lower than those on the ground (unless bottom heated). When plants are placed on the floor of hoop houses that have been unheated for the most of the winter, this problem can be exacerbated. Under certain circumstances, air temperature differences of more than ten degrees Fahrenheit can develop between the benches and the eave.

Climate-sensitive crops require growers to be mindful of the unique challenges they face in their greenhouses. It is possible to use digital thermometers to measure the temperature of the air at various heights, in various parts of the greenhouse, and under various environmental conditions. Crops can be placed according to temperature requirements using this information, and chilly regions can be identified that may require horizontal air flow fans to be addressed. Soil thermometers can also be used to monitor the growing media’s temperature. At lower temperatures, growers with bottom heat systems that keep the media and roots at the proper temperature are more likely to succeed.

Many greenhouse gardeners are able to effectively grow crops at lower than ideal temperatures each year when a variety of crops are grown together. Crop growers study the temperature requirements of their crops and the various temperatures of different locations, and they try to match them as closely as possible. Because of this, they’ve come to realize that the quality of their crops could be adversely affected. Individual circumstances must be taken into account when deciding whether or not to grow cool.

How To Prepare A Greenhouse Petunia For Planting - Krostrade

Periodically Reducing Greenhouse Temperature and Minimizing Supplemental Light

During chilly, cloudy days, can a farmer lower the greenhouse temperature and turn off supplemental lighting (unless they are being used for photoperiodic or day extension purposes)? For up to days each week with low influence on timing and plant quality, USDA-ARS greenhouse research in Toledo, Ohio has revealed. Plants such as begonia, impatiens and pansies, as well as petunas ranging from “Supertuna Vista Bubblegum” and “Supertuna Mini Strawberry Pink Veined” to “Angelface Blue” and “Luscious Citrus Blend” were used to demonstrate this effect. Angelonia had a six-day delay in blossoming as a result. Growers can lower greenhouse temperatures, close the shade curtain, and turn off supplemental lighting for one or two days a week for many crops if the weather is predicted to be cold and gloomy. If you wait any longer, your flowers will be delayed and your growth will be slowed. Additional crops need to be tested. See the following article for further information: Reduce the Cost of Greenhouse Energy Using a New Approach. Lowering the temperature of the greenhouse may lead to an increase in the relative humidity, which could lead to an increase in the prevalence of Botrytis and other leaf diseases.


Petunias are easy to cultivate and produce in a greenhouse, according to numerous university extensions. What are the ideal greenhouse temperatures for growing petunias? When it comes to growing petunias, the greenhouse temperature has a big impact.

Temperature requirements vary according to the stage of growth, whether it’s planting, rooted, or growing. Petunia germination, growth, and quality can be affected if you don’t meet these requirements. Petunias prefer temperatures of 64 to 75°F during the day and 55 to 64°F at night. Knowing your planting zone will also help you anticipate the temperatures in your location.