Worried about your plants in mid-May? Cold Zośka and the Ice Saints is a period between May 12th and 15th when late frosts can destroy all your gardening efforts. Temperatures can drop to as low as -10°C near the ground. Did you know that meteorological studies show a 40% probability of frost occurring during this time? Your young plants, heat-loving vegetables, and flowering fruit trees are most at risk. When is Cold Zośka? The end of this cold period falls on May 15th. After this date, you can breathe a sigh of relief! In this article, we will show you how to effectively protect plants from frost, using proven methods. You will learn how to use agrotextile, a foil tunnel, and other practical solutions. You will also get to know the meteorological reasons for May temperature drops. Thanks to our tips, prepare your garden for this difficult period and enjoy beautiful plants all summer long!
When are the Ice Saints and Cold Zośka? Dates and Tradition
The tradition of the Ice Saints and Cold Zośka dates back to centuries of climatic
observations made by our ancestors. Farmers and gardeners for generations noticed that the last spring frosts occur on these specific days. After them, you can safely plant sensitive plants in your garden. These names originate from the liturgical calendar and are associated with saints celebrated in mid-May. This phenomenon was noted in the cultures of the nations in this part of Europe due to its cyclicity, severity, and impact on agriculture. Meteorological observations conducted by the Astronomical Observatory of Jagiellonian University over 100 years confirm the probability of a weather breakdown between May 10th and 17th. Interestingly, similar terms for cold days in May also exist in other European countries. In Germany, the days from May 11th to 15th are called Eisheiligen, in the Netherlands IJsheiligen, in France from May 11th to 13th there are the Saints de Glace, and in Slovenia from May 11th to 15th we have Trije ledeni možje and Poscana Zofka. Polish folk proverbs, such as "Pankracy, Serwacy, Bonifacy, bad lads for the garden" or "Saint Zofija unfolds the ears of grain," are passed down from generation to generation. Although today plant protection methods are much more advanced, the tradition associated with the Ice Saints still lives on in the consciousness of gardeners. According to the proverb, this period marks the last days of spring frosts, after which the cold should no longer harm your plants.
The Three Gardeners - May 12, 13, and 14
The Ice Saints are three consecutive days falling on May 12th, 13th, and 14th, associated with the commemoration of three martyred saints. On these days, the name days of St. Pankrac (May 12th), St. Servatius (May 13th), and St. Boniface (May 14th) are celebrated. They are also called the three frozen ones, the ice men, or May frosts. St. Pankrac lived only a dozen years in the 3rd century AD and was beheaded for his faith in Phrygia. St. Servatius was a bishop in Tongres, Belgium after 345 and went down in history as an advocate of the cult of the Mother of God. St. Boniface was executed in ancient Rome during the reign of Emperor Diocletian.
Cold Zośka - May 15
Cold Zośka falls every year on May 15th, on Zofia's name day, hence the name of this phenomenon. In 2026, Cold Zośka is on a Friday. This day also marks the feast of St. Isidore, patron of farmers and advocate during droughts. St. Zofia was a Roman woman living in the 2nd century, who, according to tradition, refused to worship the goddess Diana. It is assumed that after May 15th, nights should be free from sub-zero temperatures. This day marks the boundary for the occurrence of frosts.
Where do these names come from?
The names of the Ice Saints and Cold Zośka come from the patrons of individual days in the liturgical calendar. These saints actually have nothing to do with this climatic phenomenon, nor were they gardeners by profession. The phenomenon was attributed to the patrons commemorated at this time in the liturgical calendar exactly when the last May frosts occur. The name Pankracy means "the one who has everything," Serwacy means "the one who has been saved," Bonifacy means "doing good," and Zofia means "wisdom." Thanks to many years of atmospheric observations, it has been noticed that a weather breakdown very often occurs precisely on the name days of these saints. The fact that they patronize the May cold is a pure coincidence related to the time of their veneration in the liturgy of the Church.
Why do frosts occur in May? Meteorological reasons
May frosts are not a coincidence. The phenomenon associated with the Ice Saints and Cold
Zośka has solid scientific foundations and results from specific atmospheric processes. In Central Europe, it occurs almost every year - in the years 1881-1980, May cold snaps occurred in as many as 95 years. The probability of a temperature drop in mid-May for our area is 34 percent. The highest risk of cooling is between May 10th and 17th. Why then? May is a transitional month in which winter baric systems give way to summer ones. The cause of cooling are high-pressure systems stationed over Western Europe and low-pressure systems from the eastern part of the continent. Frosts can reach up to 2 meters high - then we speak of spring frosts. Your plants closest to the ground are most at risk. Right at the soil surface, ground frosts occur, reaching up to 5 cm above the soil. The scale of damage depends on the duration of the frost, air humidity, and the sensitivity of individual varieties.
Inflow of Arctic air
After a period of warm days, the wind direction suddenly changes. Cold polar or arctic air flows from the north over Central Europe. The Arctic-continental air mass travels from the far North, through Scandinavia and the Baltic Sea. This air is dry and very cold - in spring it brings these dangerous frosts. Advective frosts are caused by the inflow of cold masses from the northeast, less often from the north. May has the maximum frequency of this air mass, which appears in Poland only 10 percent of the days in a year. This is a huge threat to your field and orchard crops.
Heat radiation from the soil
When the sky becomes cloudless and the wind dies down, something dangerous happens to plants. Radiation occurs - the emission of heat from the soil into the atmosphere. The earth, heated during the day, quickly loses energy at night. A cloudless sky causes the heat accumulated on the earth's surface to be released into space. Radiative frosts are caused by the cooling of the lower layers of the air. Heat from the ground radiates into space, unconstrained by a cloud layer. The temperature drops sharply, reaching a minimum between 4:00 AM and 6:00 AM. Remember: the closer to the ground, the lower the temperature.
How much can the temperature drop?
Temperatures during May frosts range from 0 to even -3 degrees Celsius. Minimum temperatures vary from -2 degrees in the south to 5 degrees by the sea. In the northeast of the country, the temperature can drop to -8 degrees. It happens that the temperature drops by more than 10 degrees in one day. The record frost in May was recorded on May 10, 1941, in Mława - the thermometer showed -8.5 degrees. The lowest temperature during the Ice Saints was recorded on May 12, 1978, in Krzyż Wielkopolski: -7 degrees. Now you understand why plant protection during this period is so important!
Which plants are at risk from May frosts?
Are you wondering which plants in your garden might suffer during the Ice
Saints? The sensitivity of plants to May frosts depends on their origin and stage of development. Heat-loving species and those that start vegetation early are most exposed. Frosts are particularly dangerous for plants from warmer climatic zones. They can cause damage and weakening of the most sensitive species, weaker growth, flowering, and greater susceptibility to diseases. The greatest damage occurs with large amplitudes of day and night temperatures. Remember that flowers, flower buds, young shoots, and fruit settings are most sensitive to frost. One cold night may be enough for sensitive balcony plants to lose their leaves or completely die. The second decade of May is considered the most dangerous.
Heat-loving vegetables - tomatoes, cucumbers, peppers
If you grow heat-loving vegetables, be especially careful. Tomatoes die at -1°C. Freshly planted tomato, pepper, and squash seedlings can suffer the most from frost. Cucumbers are exceptionally sensitive - frost can destroy an entire seedling in one night. Peppers, zucchinis, and pumpkins have delicate leaves that wilt very quickly after contact with frost. Pay special attention to cucumbers, tomatoes, peppers, and pumpkins in your garden. Temperatures below 0°C cause fluids in cells to crystallize.
Balcony and ornamental flowers
Do you have beautiful flowers on your balcony? Heat-loving plants such as geraniums, surfinias, or begonias do not tolerate temperatures below zero. Therefore, do not permanently place balcony plants outside until after the Ice Saints and Cold Zośka, i.e., after May 15th. Geraniums, surfinias, lobelias, or begonias are very sensitive to cold, and even a light frost can completely destroy them. Geraniums, magnolias, hydrangeas, cherry laurels, or surfinias are most often damaged. Check if you have magnolias or plane trees in your garden - their flowers and leaves are often damaged when temperatures drop below 0°C.
Fruit trees and shrubs in the flowering stage
The flowering of fruit trees is a critical moment for fruit development and yield size. Stone fruit trees bloom earlier than pome fruit trees and are therefore more susceptible to late spring frosts. Late spring frosts, i.e., temperatures from -1°C to -8°C, occur quite regularly in orchards. The greatest risk of damage from frost concerns trees that are not very frost-resistant and start blooming earlier - apricots, peaches, plums, and cherries. If you have an orchard, pay special attention to apricots, peaches, cherries, apple trees, pear trees, and black and red currants.
Young plants and freshly planted seedlings
Young plants are particularly vulnerable because their tissues are still soft, and their root system is not fully developed. This limits their ability to absorb water and nutrients. Check your young conifers - new growths of firs, especially the buds of lateral branches, walnuts, black locusts, ash trees, and many evergreen species are sensitive to frost. Coniferous plants, such as young yews and spruces, will not tolerate frosts well. Also, pay attention to species grown in containers, such as petunias, impatiens, bidens, and bacopa.
How to protect plants from May frosts? Proven methods
Effective frost protection in May doesn't have to be complicated. The simplest
solutions often work best! Agrotextile, foil tunnels, and evening watering are proven methods that you can use without much effort. Also, use homemade methods with materials you have at hand. Remember a few key rules. Moist soil stores heat better than dry soil, thus delaying cooling. Mulching acts as a natural insulation protecting the roots. Potted plants are easiest to move to a safe place. Apply covering materials in the evening before sunset, and remove them in the morning after the threat has passed. A combination of several methods gives the best results. Proper protection will save your entire growing season!
White agrotextile - the most effective protection
White agrotextile is a polypropylene material that allows air and water to pass through. Choose spring weights of 17-30 g/m² - it protects against frosts down to -3/-4°C. The white color reflects sunlight, preventing plants from overheating. Spread it loosely directly over the plants, and cover the edges with soil. You can water calmly through the material. Simple and effective!
Foil tunnel - when and how to use it
A foil tunnel creates a microclimate that raises the temperature by several degrees. Install it at a temperature of 15-20°C on a windless day. Bubble thermal insulation film reduces heat loss by 30%. Drive the PVC pipe frame into the ground to a depth of 20-30 cm. Water the plants in the evening. Use the thermal capacity of water! Moist soil retains heat during the day and releases it at night. Water 2-3 days before the expected frost. Moderate humidity protects roots from freezing.
Cloches, cardboard boxes and plastic bottles, and mulching
Plastic bottles with the bottom cut off act as mini-greenhouses. 5-liter bottles will work for larger seedlings. By removing the cap, you regulate ventilation. Cardboard boxes and paper cones should be placed an hour before sunset. A 5 cm layer of mulch insulates the soil from cooling. Bark, straw, or compost act as natural thermal insulation. Mulching eliminates temperature differences between day and night. An added bonus? Organic mulch enriches the soil with nutrients.
The period of the Ice Saints and Cold Zośka does not have to mean disaster in your garden. Now you know how to effectively protect your plants from May frosts. Agrotextile, foil tunnels, and other proven methods are your best weapon against the cold. Remember: observe the weather forecast and act proactively. Don't wait until the temperature drops! Thanks to these simple but effective methods, your tomatoes, balcony flowers, and fruit trees will safely pass through this difficult period. After May 15th, you can fully enjoy your garden and summer crops. So, invest in appropriate protection today and create conditions for your garden to flourish all summer long. Don't let Cold Zośka ruin all your hard work!