Arugula, also known as rocket, is a leafy green celebrated for its distinct peppery flavor. As a member of the Brassicaceae family, this plant is naturally suited for cooler weather, thriving when many summer vegetables have faded. Gardeners often look to extend their harvest into the fall and winter, raising the question of how much cold the plant can handle. Understanding its cold tolerance is the first step in successfully growing this crop past the traditional growing season.
Temperature Thresholds for Survival
Arugula is classified as a frost-tolerant vegetable, meaning it can withstand temperatures below the freezing point of water for brief periods. The plant’s overall survival depends on the severity and duration of the cold event. A “light frost,” which typically occurs when temperatures dip between 28°F and 32°F, is generally tolerated by mature arugula plants without lasting damage.
The true danger comes with a “hard freeze,” defined as temperatures falling consistently below 28°F. While established plants may survive a short dip to around 25°F, sustained temperatures below this point become lethal. Some specialized, extremely cold-hardy varieties are documented to survive temperatures as low as 22°F, but most common garden types will experience significant damage. A plant that has had time to mature and develop a robust root system will possess greater cold tolerance than a young, tender seedling.
Physical and Flavor Changes After Frost Exposure
Arugula exposed to extreme cold often shows visible signs of cell damage due to the freezing of water within the plant tissue. After a hard freeze, the leaves may take on a water-soaked appearance and become wilted or mushy once they thaw. This breakdown of the leaf structure, sometimes leading to browning, is known as necrosis and renders the foliage undesirable for harvest.
Conversely, exposure to a light frost can actually improve the flavor profile of the leaves. This beneficial change is due to a natural defense mechanism where the plant converts its stored starches into sugars. This increase in sugar concentration acts as a form of natural antifreeze, lowering the freezing point within the plant’s cells. The result is that the harvested leaves often taste less bitter and acquire a noticeable sweetness, making them more palatable than those grown in the heat of summer.
Methods for Extending the Arugula Harvest Season
Gardeners can push the harvest season past the plant’s natural cold limits by employing various protective measures. One of the simplest strategies involves using floating row covers, which are lightweight fabric materials draped over the plants. These covers trap heat radiating from the soil, creating a microclimate that can raise the surrounding air temperature by several degrees.
For more substantial protection, gardeners can install a thick layer of organic mulch, such as straw or shredded leaves, around the base of the plants. This mulch acts as an insulating blanket for the soil, helping to maintain a warmer environment for the root system. Protecting the roots is paramount, as the health of the crown determines the plant’s ability to regrow once milder weather returns.
The most significant extension of the growing season is achieved with structures like cold frames or hoop houses. These enclosures function as miniature greenhouses, offering superior insulation and shelter from wind and precipitation. Cold frames use a transparent lid to capture solar energy, allowing gardeners to maintain temperature control and harvest fresh arugula even when outdoor temperatures remain below freezing for extended periods.