Cloches and Bell Jars: Mini Greenhouses for Early Starts and Winter Protection

A cloche (French for "bell") is a transparent cover that traps solar heat, creating a microclimate around a single plant. Traditional glass bell jars had glass handles that focused light like a laser — modern versions use wood or plastic. Today, cloches range from elegant glass to DIY milk jugs. All extend your season.

Types and Uses

• Glass cloches/bell jars: Beautiful, heavy, excellent heat retention. Best for small, high-value plants.
• Plastic water-filled cloches: Cheap, lightweight, self-venting (water expands/contracts).
• DIY: Milk jugs (bottom removed), 2L bottles, wire frames + clear plastic.

When and How to Use

• Spring: Start tomatoes, peppers, basil 2–4 weeks early. Place over plants at planting.
• Fall: Extend harvest of greens, herbs.
• Winter: Overwinter marginally hardy plants (rosemary, lavender in cold zones).

Critical: Ventilation

On sunny days, temperatures inside can soar. Prop the edge with a stick or rock to vent. Cooked plants are a real risk.

Best Candidates

Tomatoes, peppers, eggplant, basil, melons, cucumbers, tender perennials, early bulbs. Not for large or sprawling plants.

Cloches are the simplest season extenders — no electricity, no complexity, just physics.