How Cold Can Ferns Tolerate?

Ferns, with their delicate fronds and graceful appearance, have been gracing our gardens and homes for centuries. A staple in both indoor and outdoor gardening, ferns come in various species, each with its own unique temperature preferences.

Understanding how cold ferns can tolerate is essential for their care, especially if you plan to keep them outdoors during the cooler months.

Understanding Fern Hardiness

“Fern hardiness” essentially refers to the fern’s ability to withstand and thrive in various climatic conditions, particularly in terms of temperature tolerance. The original habitat of a fern species, its evolutionary history, and its genetic adaptations play pivotal roles in determining its hardiness.

Origins Matter

To truly grasp the hardiness of a fern, it’s crucial to look at its natural habitat:

• Tropical Ferns: These ferns hail from regions near the equator where temperatures are warm year-round. Their hardiness is more attuned to handling variations in moisture rather than cold.
• Temperate Ferns: Ferns from temperate zones, which have distinct seasonal changes, tend to be more adaptable to colder conditions. They’ve evolved to tolerate a certain amount of chill and may even go dormant in winter.
• Alpine and Arctic Ferns: Few ferns like the Alpine Woodsia originate from extremely cold regions. They are accustomed to freezing temperatures and brief growing seasons.

Deciduous vs. Evergreen Ferns

Hardiness can also be understood in the context of a fern’s lifecycle:

• Deciduous Ferns: These ferns lose their fronds during the winter, conserving energy and resources. The lack of foliage can be a protective mechanism against frost and cold damage. In spring, they sprout new fronds.
• Evergreen Ferns: While these ferns retain their fronds year-round, they are not necessarily tropical. Many evergreen ferns from temperate zones have robust fronds that can withstand cold and remain green throughout winter.

Indicators of Hardiness

Here are a few pointers that can hint at a fern’s hardiness:

• Frond Texture: Often, but not always, ferns with thicker, leathery fronds are better at withstanding cold compared to those with delicate, thin fronds.
• Root Systems: Ferns with deep, extensive root systems can tap into the earth’s insulating properties, making them more cold-hardy.
• Growth Patterns: Ferns that grow close to the ground, forming rosettes or mats, can benefit from the soil’s warmth, helping them endure colder temperatures.

USDA Hardiness Zones

A practical way for gardeners to gauge a fern’s hardiness is by referring to the USDA Hardiness Zone Map. Each fern species will typically have recommended zones, indicating where they can thrive year-round. For example, a fern hardy in Zones 4-8 can typically survive winters in those zones without extra protection.

Hardy Ferns

Some fern species are particularly resistant to cold. These hardy ferns can endure freezing temperatures and even come back after a winter snowfall. A few examples include:

• Ostrich Fern (Matteuccia struthiopteris): This fern is known to survive temperatures as low as -30°F (-34°C).
• Christmas Fern (Polystichum acrostichoides): This can endure temperatures down to -5°F (-20°C).

Tender Ferns

Tender ferns are the ones that primarily come from tropical or subtropical regions. They are more sensitive to cold temperatures and can get damaged with a light frost. For these ferns, temperatures below 50°F (10°C) can be harmful.

• Boston Fern (Nephrolepis exaltata): A popular houseplant, the Boston fern can start to suffer when temperatures drop below 50°F (10°C).

Protecting Your Ferns in Cold Weather

Ferns, whether planted in the ground or in pots, need special care during colder months, especially if the temperatures are expected to drop below their tolerance level. Here’s how you can ensure your ferns weather the chill:

1. Mulching

Mulching provides several benefits:

• Insulation: A 2-4 inch layer of mulch can help maintain a more stable soil temperature, preventing rapid temperature fluctuations that can harm plant roots.
• Moisture Retention: Mulch helps the soil retain moisture, which can be beneficial during cold, dry periods.
• Protection: Organic mulch will decompose over time, enriching the soil and providing vital nutrients for the ferns.

2. Repositioning Potted Ferns

Potted ferns are more exposed to cold as their roots don’t have the insulation provided by the ground. During cold spells:

• Bring Indoors: Consider moving your potted ferns indoors, either in a sunroom, garage, or even a well-lit room.
• Sheltered Outdoors: If bringing them inside isn’t feasible, relocate them to a more sheltered spot outdoors, such as against a wall or under a porch.

3. Watering Before a Frost

Moist soil retains heat better than dry soil. Watering the ferns’ soil (not the fronds) the evening before a frost can help keep the ground slightly warmer.

4. Covering Ferns

Covering ferns can be particularly effective against unexpected frosts:

• Materials: Use frost cloths, burlap, old sheets, or even newspapers. Avoid using plastic directly on the plants as it can exacerbate the cold damage.
• Installation: Drape your chosen material over the ferns in the evening and secure it so it doesn’t blow away. It’s preferable for the material to reach the ground, trapping heat rising from the soil.
• Removal: It’s crucial to remove the covers during the day, especially if the sun is out, to prevent overheating and to allow the plants to breathe.

5. Anti-desiccant Sprays

These sprays can form a protective layer on the fern’s fronds, reducing moisture loss during dry, cold spells. However, always read the label and ensure they’re safe for ferns before use.

6. Create Windbreaks

Cold winds can be just as damaging as frost. Erecting temporary windbreaks using burlap or other materials can shield delicate ferns from damaging cold winds.

7. Regularly Check Weather Forecasts

Stay informed about upcoming cold fronts or unexpected frosts. This gives you time to prepare and protect your ferns adequately.

FAQs on Ferns and Cold Tolerance

Also, you may like some more gardening articles:

• How Often Should You Water Ferns?
• What is the Best Fertilizer For Ferns?
• What to Plant with Ferns [Complementing the Green Fronds]
• When to Bring Ferns inside?
• Why are Algae and Ferns both Green?
• How to Grow Ferns From Spores
• How to Keep Ferns from Growing Back?

In conclusion, ferns are versatile plants, with different species having varying levels of cold tolerance. Whether you’re a novice gardener or a seasoned horticulturist, understanding the cold tolerance of ferns will ensure they flourish in their environments.

Always research the specific needs of the fern species you have or intend to get. With proper care and precautions, you can enjoy their beauty year-round!