Hydrofarm Jump Start Windowsill Heat Mat | 3 x 20 in, 7.3W, 120V

What the Jump Start Windowsill Heat Mat Does

This narrow pad sits under seed trays, pots or cell strips and warms the medium from below. It measures 3 x 20 in, the right shape for a window ledge, a bookshelf or a single row of small pots. At 7.3 W on 120 V, it draws only 0.06 A, so it costs very little to run around the clock. The mat lifts root-zone temperature 10 to 20 °F above the surrounding air. Warm media speeds germination and pushes early root growth, especially in a cool house or a draughty window. It heats only the soil, so the room itself does not need to be kept warm for seedlings. The surface stays warm rather than hot, so it will not mark a painted sill. Construction is waterproof, and lighting, watering and planting tips are printed on the mat. A 6 ft power cord plugs into any household outlet, and the mat is UL listed. It also fits the Jump Start Mini Germination Station (JS24GPM), and Hydrofarm covers it with a 1-year warranty.

Starting Seeds on a Seedling Heat Mat

A seedling heat mat pays off most in late winter and early spring, when windowsills run cold at night. Lay the mat flat on a dry surface and set trays or pots directly on top. Fill cells with moist, not soggy, starting mix before sowing. Cover the tray with a humidity dome until most seeds have sprouted. Peppers, tomatoes, basil and other warm-season crops respond best to the extra bottom heat. Check moisture daily, since a warm medium dries out faster than a cold one. Once seedlings are up and growing strongly, move them off the mat or unplug it during warm days. Use a separate thermostat if seeds need a precise temperature rather than a fixed rise over ambient. Keep the cord away from standing water and drip trays, even though the mat itself is waterproof. Wipe it clean between batches and store it flat so the heating wire is not kinked.

Key Features

• 3 x 20 in size: Fits a window ledge or narrow shelf.
• 10 to 20 °F rise: Warms the root zone over ambient.
• 7.3 W, 120 V: Draws only 0.06 A from a household outlet.
• Waterproof and UL listed: Safe for daily use under trays.
• 6 ft cord: Reaches a wall outlet from the sill.

Technical Specifications