Celery's ability to endure frost in the winter months is surprising for most gardeners who grow this vegetable in an outdoor environment. Mature celery can withstand 28°F (-2°C) as long as some protection is provided, but in my trials in Zone 6b, my plants at this temperature were completely lost at 25°F (-4°C). This has a lot to do with pre-freeze prep. I harden off my plants with cold frames weeks before I receive the first freeze warning.
Frost Protection
- Use double-layer row covers below 32°F (0°C)
- Install hoops to prevent contact with frozen leaves
- Remove covers daily above 40°F (4°C) for airflow
Overwintering in Zones 8+
- Apply 6-inch straw mulch around plant bases
- Wrap trunks with burlap below 28°F (-2°C)
- Prune yellowed outer stalks monthly
Indoor Transition
- Dig plants before first frost with 12-inch root ball
- Use 5-gallon buckets with drainage holes
- Maintain 55-65°F (13-18°C) near south windows
Soil Preparation enhances winter hardiness. During the previous year, I incorporated 3 inches of compost into the beds before the fall rains; the organic matter served to insulate the roots. Do not apply fertilizers with a high nitrogen content after September, as they will induce soft or tender growth that will be instantly killed by frost. Instead, apply potassium once a plant's growth has slowed in the fall to strengthen cell walls.
Signs of Frost Harm
- Transparent, waterlogged leaves
- Blackened stem bases
- Mushy roots upon digging
Salvage Methods
- Cut damaged foliage above growth nodes
- Drench soil with 60°F (16°C) water at dawn
- Apply seaweed extract to reduce shock
Where growing zones are 7 or less, grow celery as an annual and start from seed each spring. My growing-in-containers solution - 10-gallon fabric pots - allows me to bring plants indoors as temperatures drop. Celery plants grown over the winter under LED grow lights produced 60% more stalks than similarly aged celery started from seed in the spring.
Read the full article: How to Grow Celery: Expert Homegrown Guide
