Are heat mats worth it?

Heat mats are a popular way to provide bottom heat to plants and seedlings. But are they really necessary? Here we’ll examine the pros and cons of heat mats to help you decide if investing in them is worthwhile for your needs.

What are heat mats?

Heat mats, also known as seedling heat mats or germination mats, are flat electric heating pads designed to provide warmth from underneath plants and seed trays. They come in a range of sizes from small mats for starting individual seed trays to larger under-bench mats that can span the bottom of a whole greenhouse shelf or seed starting rack.

Heat mats usually provide a consistent low-level warmth between 10-20°F above the ambient air temperature. They work by running an electric current through internal resistive wiring to produce gentle heat. The mats have an internal thermostat to maintain the desired temperature.

Benefits of using heat mats

There are a few key benefits that heat mats can provide:

• Faster germination – Warmth from below accelerates the germination process and gets seeds sprouting sooner. This allows you to transplant seedlings into the garden earlier for a longer productive season.
• More uniform germination – The consistent warmth encourages faster and more uniform sprouting across all the seeds. You’ll get less stragglers lagging behind.
• Better seedling growth – Warm roots and warmer overall soil temperature encourages faster seedling establishment and growth after germination.
• Allows earlier seed starting – Heat mats enable you to start planting seeds indoors 4-6 weeks before last frost. This gives long season crops like tomatoes and peppers a head start on the growing season.
• Prevents leggy seedlings – The bottom heat minimizes the need to start seedlings in warmer ambient air temperatures. This results in stockier, healthier seedlings instead of tall, leggy ones.
• More control over soil temperature – Heat mats let you dial in an optimal soil temperature for germination and prevent extremes in cold weather.
• Versatility – In addition to seed starting, heat mats can also provide warmth for root cuttings, keeping tropical plants happy, creating seedling hotbeds, and other applications.

Potential drawbacks of heat mats

Heat mats have some potential downsides to consider as well:

• Added expense – Buying heat mats and controllers or thermostats represents an added upfront cost and investment.
• Ongoing energy costs – Electricity to run the heat mats will add to your ongoing utility bills.
• Risk of overheating – Mat surface temperatures can sometimes get too hot without proper regulation, risking dry out or damage to plants.
• Dry out problems – The added heat speeds evaporation, so plants may need more frequent watering.
• Not universally needed – Some seeds and plants don’t require bottom heat for good germination. Brassica crops like cabbage, for instance.
• Added equipment – Heat mat setups require temperature controls and mats take up space that may be limited.
• Can encourage mold growth – The higher heat and humidity levels can foster mold growth if airflow is inadequate.

When are heat mats most useful?

While heat mats are not essential across the board, there are some situations where they can prove exceptionally helpful:

• Starting warm weather crops like tomatoes, peppers, and eggplants indoors early in cool weather.
• Germinating challenging seeds like basil, oregano, lemongrass, and lavender.
• Sprouting tender perennials from seed such as petunias, lobelia, and begonias.
• Getting a jump start on melons, cucumbers, and squash by warming up the soil earlier in spring.
• Maintaining ideal soil temperatures for tropical plants like anthuriums and orchids.
• Rooting tricky plant cuttings of shrubs and houseplants.

Most vegetables, annual flowers, and half-hardy perennials appreciate the accelerating effects of bottom heat on germination. Just be sure your starting medium doesn’t completely dry out.

Types of heat mats

There are a few different heat mat configurations to choose from:

• Small propagation mats – Designed to fit under one or a few seed trays, these typically provide 10-20 watts and get up to 20°F above room temperature. Useful for starting seeds and cuttings.
• Germination heating pads – Low profile, flexible polyethylene mats that can be rolled up when not in use. Range from around 20-80 watts.
• Large seedling heat mats – Usually made of silicone rubber and cover the bottom of a whole seed starting rack or shelf. Get up to 10°F warmer than room temperature.
• Flexible heat mats – Softer thin mats that bend to contour to shelving or other structures in propagation areas and greenhouses.
• Waterproof heat mats – For providing warmth in high humidity situations like terrariums, indoor ponds, and foggy greenhouses prone to condensation.
• Outdoor heat mats – Heavy duty and weatherproofed mats designed to create hotbeds outdoors for an early start on the growing season.

Smaller propagation mats and germination pads are the most popular options for home gardeners and indoor seed starting. Larger mats are often used in commercial greenhouse production.

How to use heat mats effectively

Follow these tips to get the most out of your heat mats:

• Read and follow the manufacturer’s instructions for safe operation.
• Always use a temperature control device like a thermostat or rheostat to regulate heat and prevent overheating.
• Ensure proper airflow over mats to avoid localized hotspots.
• Monitor moisture levels closely and water more frequently to compensate for quicker evaporation.
• Lift seed trays off mats once sprouted to avoid stressing young seedlings.
• Use insulation under and around mats to direct warmth upwards into planting containers.
• Limit mat use to starting and rooting rather than long term plant growth.
• Invest in a quality temperature controlled propagation station for the most dialed-in regulation.

With proper set up and attentive monitoring, heat mats can give your seeds and cuttings the nurturing warmth needed for the best possible start on life.

Recommended heat mats

Here are some highly rated heat mats to consider:

Heat Mat	Key Features
VIVOSUN Seedling Heat Mat	– 10″x20.5″ size – 10 watt output – Waterproof – Foil construction
HC Companies Seedling Heat Mat	– 20″x48″ size – 68 watt output – Durable silicone – 1 year warranty
Microclimate Propagation Mat	– 7.5″x19.5″ size – 18 watt output – Max 122°F temperature – Teflon coat
Grower’s Edge Seedling Heat Mat	– 20″x48″ size – 68 watt heating – Integral 5′ power cord – Rubber enclosure
Hydrofarm Seedling Heat Mat	– 10″x20″ dimensions – 19 watt heating – Water resistant – 1 year warranty

Vivosun and Hydrofarm are two very popular brands of propagation heat mats. Most heat mats cost $25-50 depending on size and features.

Heating alternatives

If you decide heat mats are overkill for your needs, there are a couple DIY approaches to providing seedlings warmth:

• Place seed trays on top of a working fridge, water heater, or other appliance – This takes advantage of the ambient heat given off by household appliances to naturally warm from below.
• Make a DIY propagation tray heater – You can create your own safe and effective seedling heating tray by embedding water tubing or low wattage rope lights in the bottom of a tray filled with sand or soil.

While less regulated, these methods allow you to skip purchasing dedicated heat mats.

Key takeaways

Here are the key points to remember when deciding if heat mats are worth utilizing:

• Heat mats provide constant low-level bottom warmth optimal for starting seeds and cuttings.
• They accelerate germination and improve seedling vigor but are not mandatory for all plants.
• Use heat mats for giving tender, heat-loving plants an early start on the growing season.
• Proper set up and monitoring is important to prevent issues like drying out or overheating.
• Alternative DIY solutions can provide seedlings warmth without buying heat mats.

Conclusion

Heat mats can be extremely useful for giving your plants the best start when you need controlled bottom warmth to spur germination and early growth. But they may be overkill for starting less finicky seed varieties or cuttings. Consider your specific needs and weigh the pros and cons before investing in propagation heat mats. With proper use and reasonable expectations, they can be an effective tool in the gardener’s arsenal.