Foxtail fern (Asparagus densiflorus ‘Myersii’) is a popular ornamental plant known for its distinctive, plume-like foliage. Its dense, upright stems, covered in soft, needle-like leaves, create a unique, fluffy appearance, resembling a foxtail. Though often called a fern, it belongs to the asparagus family and is native to the warm, humid climates of South Africa.
Ideal Temperature Range
Foxtail ferns thrive in warm conditions, preferring a temperature range of 68 to 100 degrees Fahrenheit (20 to 38 degrees Celsius) for optimal growth. During winter months, they can tolerate cooler temperatures, ideally staying above 50 degrees Fahrenheit (10 degrees Celsius). This preference for warmth allows them to grow outdoors year-round in USDA hardiness zones 9 through 11, where the climate provides consistent warmth.
Dealing with Cold Temperatures
When temperatures drop below their preferred range, foxtail ferns can experience significant damage, particularly below 25 degrees Fahrenheit (-7 degrees Celsius). Even temperatures around 20-25 degrees Fahrenheit can cause the plant to die back to the ground, though the roots may remain hardy.
To protect outdoor plants during cold snaps, apply a layer of mulch around the base to insulate roots. For potted foxtail ferns, move them indoors to a bright, warm location. Covering outdoor plants with frost cloths or old Christmas lights can provide enough warmth to prevent severe damage. Watering the plant well before a cold spell also helps it withstand lower temperatures.
Dealing with Hot Temperatures
Foxtail ferns generally tolerate high temperatures well, but prolonged exposure to intense heat and direct sun can cause stress. Temperatures above 90 degrees Fahrenheit (32 degrees Celsius) are not recommended, and extreme heat above 100 degrees Fahrenheit (38 degrees Celsius) can lead to scorching.
To mitigate heat stress, provide shade during the hottest parts of the day, especially for outdoor plants. Placing them under larger trees or using shade cloths reduces sun intensity. Maintaining consistent soil moisture through adequate watering is also important, as heat increases water evaporation. Increasing humidity around the plant, such as by misting or using pebble trays, helps it cope with dry, hot air.
Signs of Temperature Stress
Recognizing the visual cues of temperature stress allows for timely intervention. Cold damage often manifests as foliage lightening, then turning brown or black. Affected fronds may appear shriveled, wilted, or droopy; in severe cases, stems might become mushy.
Conversely, heat stress typically presents as yellowing, crisping, or browning of leaf edges and tips. The foliage might look bleached or faded from intense sunlight. Plants suffering from heat can also exhibit general wilting or drooping as they struggle to retain moisture. Stunted growth or a lack of new development can also signal ongoing temperature challenges.