How Cold Is Too Cold for Flowers to Be Outside

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What temperature is too cold for flowers?

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Flowers are not only beautiful, but they are also an important part of our landscapes. They draw bees and help plants reproduce. But despite how beautiful they are, flowers have limits regarding the environment, especially in cold weather.

Gardeners, plant lovers, and anybody hoping to grow a successful flower garden are all curious about the answer to the question, “How cold is too cold for flowers to be outside?” 

This article answers this question along with some important remarks. By learning about the weather limits that affect flowers, we can make smart choices about growing, protecting, and storing flowers outside.

How Cold Is Too Cold for Flowers to Be Outside

There are some broad answers for this subject, but before we get into them, it’s vital to note that specifics might differ depending on the plant species and where you live. For example, what works for pansies, which thrive in cooler conditions, may not work for marigolds, which thrive in hotter climates.

Most flowers will freeze when the temperature goes below 28 degrees Fahrenheit (-2 degrees C) for over five hours. However, some blossoms are better able to withstand the cold than others. For example, annuals become susceptible to frost damage when the temperature drops below 32 degrees Fahrenheit (0 degrees Celsius). On the other hand, temperatures as low as 18 degrees Fahrenheit (-7.7 degrees Celsius) won’t kill cold-hardy flowers.

Most experts say flowers and other items should be brought indoors or covered another way before the temperature falls below 45° Fahrenheit. This temperature is a bit higher, around 50 degrees, for warm-weather and tropical plants.

how cold is too cold for flowers to be outside

Species-Specific Cold Tolerance

Flowers that grow outside have different levels of cold tolerance depending on their species, genetics, natural environment, hardiness zone, how they protect themselves from cold weather, etc. Here are some of the most important things that affect how well a flower can handle cold:

Genetic Makeup

Like all other organisms, flowers have varying degrees of cold tolerance depending on their unique genetic composition. Tolerating or thriving in chilly conditions is what we mean when discussing an organism’s cold tolerance.

Due to genetic heterogeneity, the ability of various flower species to withstand cold conditions varies. In addition, individuals within a species may also exhibit variation in their cold tolerance due to genetic reasons.

Factors at the genetic level regulate whether regulatory pathways are active or inactive, which in turn affects cold tolerance. These pathways enable flowers to adjust to cold by controlling gene expression, protein synthesis, and metabolic activity. For example, the CBF/DREB1 pathway is an important regulatory mechanism that regulates cold response gene expression.

Native Habitat

A species’ natural habitat is a significant factor in determining its cold tolerance, particularly for flora. Adaptations for survival and growth in cold temperatures are often already present in plants that have developed in colder areas. 

Physiological, morphological, and metabolic modifications enhance an organism’s survival capacity in frigid environments. For example, high-altitude plants, such as those found in the alpine areas, often have smaller, thicker leaves with a waxy cuticles to assist in preventing water loss and frost damage. 

Hardiness Zones

The average annual low temperature is used to classify a region into one of many “hardiness zones,” each important to the growth of different types of plants.

Hardiness zones are an important way to determine how cold-tolerant a flower species is. The average low temperature in the winter is used to divide the world into hardiness zones. This gives a common way to determine whether a plant will grow well in a certain place. 

Each zone is given a number representing the lowest temperature predicted there. So, by looking at the hardiness zone map, gardeners and horticulturists can determine which flower species are most likely to survive the winter in their particular zone.

General Temperature Guidelines

When growing flowers outside, weather rules ensure they grow well and stay alive. Different flower types can have different needs regarding weather, but hardy, semi-hardy, and tender flower plants all have different cold tolerance

Hardy Flowers

Flowers in the hardy category may withstand colder temperatures than the other two types. These blooms are hardy to temperatures as low as 40 degrees Fahrenheit. However, hardy annual seedlings are vulnerable to a little frost.  Some hardy annual flowers are larkspur, sweet alyssum, pansy, calendula, and foxglove.

Semi-Hardy Flowers

Semi-hardy annuals can withstand temperatures below freezing. At least 40 degrees Fahrenheit is acceptable. Half-hardy annuals include flowers common as cleome, baby’s breath, forget-me-nots, and strawflowers.

Tender Flowers

Tender flowers cannot withstand any degree of frost. Temperatures lower than around 55 degrees Fahrenheit will kill these blossoms. True annuals, or tender annuals, are short-lived plants. Annuals that bloom early and die quickly include the impatiens, verbena, marigold, coleus, and begonia.

The Impact of Cold on Flowers

When temperatures drop, and it gets cold, these beautiful plants face several problems that can greatly affect their growth, development, and general health. 

Knowing how cold affects flowers is important for farmers, horticulturists, and anyone who wants to grow beautiful flower displays. Some impacts of cold on flowers are:

Dehydration

The impact of cold temperatures on flowers can have a detrimental effect, primarily through dehydration. Cold weather can make plant cells lose water, leading to dehydration and damage to the delicate parts of the flowers. In addition, when exposed to cold weather, flowers undergo a process called “desiccation,” in which the water in their cells freezes and makes ice crystals. 

As a result, the cells break, which makes the flower’s structures less stable. Also, cold air tends to be drier, which speeds up the drying-out process. The lack of water hurts the flower petals, roots, and leaves, causing the whole plant to wilt, turn brown, and shrink. 

Frost Damage

Frost is one of the most dangerous things for flowers during cold times. Frost damage can show up as dark, wilted, or fall flowers, hurting their looks and growing ability.

Frost can cause the water inside the plant cells to expand and shrink, which damages their walls and messes up important metabolic processes. Flowers that aren’t used to cold temperatures or are in a sensitive stage of growth, like young buds or open flowers, are more likely to be hurt by frost. 

Freezing Damage

Ice crystals form outside and inside plant cells when the temperature goes below freezing (0°C or 32°F). This is called freezing damage. These ice crystals can cause a lot of damage to cells and mess up important bodily processes. In addition, when water freezes, it gets bigger. This can break the cell walls and membranes of flowers, which can’t be fixed. 

The damage caused by freezing depends on many things, like how long and cold it is, how hardy the flowers are, and where they are in their growth cycle. Flowers like buds or blooms are especially at risk in fragile states. 

Strategies for Protecting Outdoor Flowers

You don’t want the flowers you worked so hard to grow to perish in a snowstorm or frost. Of course, moving your flowers inside and out of the cold is ideal, but that is only sometimes possible. 

We’ll review some tips for keeping the flowers blooming during winter.

Mulching and Insulation

Mulching covers the ground surrounding a plant’s roots with a layer of organic or inorganic material. This may be anything from straw to wood chips to shredded leaves. 

This shield has many functions. First, it insulates the soil, making it a more consistent temperature for the plants to flourish. This insulation keeps soil temperatures from swinging too much in either direction, protecting a plant’s roots. It also aids in soil moisture retention, which reduces evaporation and guarantees a steady water supply for the blossoms.

Protective Covers and Structures

Coverings like yard cloches or frost blankets protect flowers from bad weather. They act as shields against cold, wind, heavy rain, or hail, keeping flowers from coming in direct touch with things that can hurt or kill them. By making a barrier to protect the plants, these covers help keep a stable environment around them. This keeps the plants warm and reduces temperature changes.

Flowers that grow outside can be kept in a controlled environment with the help of buildings like greenhouses and cold frames. These buildings keep the sun’s heat inside, warmer the area than the outside temperature. 

Watering Techniques

Watering your flowers first thing in the morning during cooler weather is best. Because of this, the plants will have time to absorb the water before the temperature lowers at night. Staying out of the leaves is another good way to avoid getting frostbite.

A radiator effect may be created for your plants by nestling jugs or containers of water that warm in a layer of hay mulching for further protection. This will protect them from the frost and give their roots a better chance to take hold.

Heat Sources

Heat sources can protect flowers outside by keeping them warm and making the surroundings good for growing. In addition, these heat sources help protect flowers from cold, snow, and other bad weather conditions, ensuring they stay healthy and full of life.

Portable heaters or heat lamps are often used to keep warm. These gadgets can send controlled heat to flower beds or individual plants. By putting the heat source in the right place, gardeners can raise the temperature around it, preventing frost and keeping delicate flowers from dying.

Monitoring and Recovery

Monitoring means watching the flowers and regularly judging their health, growth, and conditions. By closely monitoring the plants, gardeners can quickly spot signs of worry, disease, bugs, or external factors hurting their flowers. Early discovery lets people act quickly and take the right steps to limit any possible damage. 

When outdoor flowers get hurt or stressed, steps are taken to help them get better. These steps can include cutting off damaged or sick parts, getting rid of bugs or insects, giving the plant the right amount of water, and adding nutrients or fertilizers as needed. 

FAQ

What is the lowest temperature for outdoor flowers?

The lowest temperature for outdoor flowers is 50 degrees Fahrenheit. 

Will 18 degrees kill flowers?

Most perennial flowers will perish when the temperature drops below 18 degrees Fahrenheit, but there is a catch. Some cold-hardy blooms may be able to endure overnight lows of 18 degrees Fahrenheit if the temperature stays that low for just a few hours.

When should I put my flowers outside?

Plants should not be put outdoors until the threat of frost has gone.

How do I revive flowers damaged by cold?

As soon as you can, bring the plant to warmer temperatures.
The plant has to be moved to a warmer location immediately. Avoid removing any leaves that seem to be dead and instead focus on warming the plant.

Final Thoughts

Growing healthy flowers might be a challenge. To ensure the healthy growth of a flower, you must know how cold it is too cold for flowers to be outside. 

However, by picking hardier flowers against frost and employing every method to keep them toasty, you may enjoy your garden’s full splendor for longer.

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Jack Daniel

I am Jack Daniel, and I have been gardening for more than 20 years now. I believe that with my years of experience, I can help you with backyard ideas and backyard product reviews. So, with the motto to help anyone facing gardening issues or wanting tips on enhancing the beauty of their backyards, I have created Backyard Muse. So, before anything else, I want to welcome you warmly to my site.

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