Nasturtiums are popular annuals, known for their vibrant, edible flowers and leaves. As temperatures drop, gardeners often wonder about their ability to withstand cold. Understanding how nasturtiums react to frost is important for their continued enjoyment.
Nasturtium’s Frost Tolerance
Nasturtiums are tender annuals, susceptible to cold temperatures and frost. Their resilience varies depending on the intensity of the cold event. A light frost, when temperatures dip just below freezing (0°C to -2°C / 32°F to 28°F), can cause some damage. This can cause wilting or darkening of foliage, but the root system often remains viable, allowing for recovery.
In contrast, a hard freeze (-2°C / 28°F or colder for several hours) proves fatal for nasturtiums. Prolonged exposure to such low temperatures causes water within the plant cells to freeze and expand, rupturing cell walls. This cellular damage prevents recovery, proving fatal. Gardeners should be aware of impending hard freezes.
Signs of Frost Damage
When nasturtium plants experience frost, several visual cues indicate damage. The most immediate sign is wilting, where leaves and stems lose turgidity and droop. Affected foliage may darken, often turning black or dark brown, especially along edges and tips.
The texture of the leaves and stems can change, becoming mushy or water-soaked to the touch. This soft, limp appearance indicates cellular damage from freezing. These changes help gardeners assess the extent of cold exposure.
Protecting Nasturtiums from Frost
Proactive measures can increase a nasturtium’s chances of surviving cold snaps. Covering plants is an effective method; frost cloths, old sheets, or blankets can be draped over them before sunset. Remove these covers once temperatures rise the following morning to allow for air circulation and sunlight.
Watering the soil around nasturtiums before a frost can provide protection. Moist soil retains heat more effectively than dry soil, radiating warmth throughout the night and helping to insulate the roots. For nasturtiums grown in containers, relocating them indoors or to a sheltered area, such as a garage or a covered porch, protects them from freezing temperatures. Monitoring local weather forecasts allows gardeners to anticipate cold events and implement these strategies promptly.
Post-Frost Care and Recovery
After a frost event, allow nasturtium plants to thaw naturally before assessing the damage. Rushing to prune frozen tissue can cause further harm. Once the plant has thawed, clearly damaged parts, such as blackened or mushy leaves and stems, can be carefully pruned away.
Light watering may be beneficial if the soil is dry, but it is important to avoid overwatering, which can lead to root rot. If only a light frost occurred and the plant’s root system was not compromised, new growth may emerge, especially in regions with milder climates. However, if the plant endured a hard freeze, recovery is highly unlikely, and replacing the plant is generally the most practical option.