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For many gardeners, browsing through plants in a garden center is a favorite spring pastime, but some folks can be put off by the high price and limited selection of bedding plants. Starting seeds indoors a few weeks before transplanting them in the garden saves money and allows gardeners to grow many varieties. The trouble is, some seeds are slow to sprout at room temperature—fortunately, that’s where seedling heat mats come in.
Heat mats are specifically designed to gently increase the temperature of the seed-starting medium—a terrific boon to home gardeners. When placed beneath seed trays, heat mats offer gentle warmth, just enough heat to mimic the temperature of outdoor soil on a sunny spring day. This heat encourages seeds to sprout.
The best seedling heat mats are safe, effective, and increase the seed germination rate. Ahead, learn what to look for when shopping for a heat mat, and find out why any of the following would be a beneficial addition to an indoor gardening tool collection.
- BEST OVERALL: Vivosun Seedling Heat Mat and Digital Thermostat
- BEST BANG FOR THE BUCK: Vivohome Waterproof Seedling Heat Mat
- BEST LARGE SIZE: iPower Carbon Film Seedling Heat Mat
- BEST STARTER KIT: Super Sprouter Premium Propagation Kit with Heat Mat
- BEST MAT SET: Propagate Pro Wrap Around Heating Pad Strip
- BEST WITH THERMOSTAT: BN-LINK Seedling Heat Mat With Digital Thermostat
- BEST FOR ROOTING CUTTINGS: AC Infinity Suncore Dual Waterproof Seedling Mats
How We Chose the Best Seedling Heat Mats
When gathering our top picks for seedling heat mats, we made sure to only include options that were made of high-quality materials to ensure they can stand up to frequent use. The products in our list of recommendations all include at least a water-resistant rating, while most are fully waterproof. All of our picks can wipe clean easily and can fold up neatly when not in use.
Many of the options on our list are also available in various sizes, so they’re able to meet most shoppers’ needs depending on their project. Options range from mats with smaller and thinner strips—ideal for wrapping around and heating up containers for rooting cuttings—to oversize mats that are suitable for large growing projects.
Lastly, depending on how specific the temperature needs to be for a given plant, shoppers have some choices. They can opt for the more affordable stand-alone mats, or they may wish to have more precise and steady temperature control with those that include thermostat controllers, which can provide more professional reliability for certain situations.
Our Top Picks
To qualify as a top pick, a seedling mat should raise and maintain the temperature in a grow tray to between 75 and 85 degrees Fahrenheit. It should also be water-resistant and well sealed. The best seedling heat mats will vary depending on how large a heating surface is desired and how many grow trays the gardener wants to warm.
If the mat is part of a humidity-controlled unit, the dome should come with ventilation to keep the seedlings from becoming overheated in direct sunshine. Any one of the following mats is well suited for helping encourage seed germination.
Best Overall
Vivosun Seedling Heat Mat and Digital Thermostat
With the ability to maintain temperatures in the optimal range of 68 to 86 degrees Fahrenheit, the Vivosun seedling heat mat is well suited to home gardeners who want to start bedding plants indoors from seed. The flat mat features a thick external layer of supple, flexible PVC, plus a layer of infrared heating film in the center. It also comes with double insulation around the edges.
The mat measures 10 inches long by 20.75 inches wide—just the right size for slipping beneath a standard growing tray. It features a controller and a thermometer probe attached to the power cord for adjusting the mat temperature while also monitoring the growing medium’s temperature. The Vivosun is IP67-waterproof rated, so it is safe to use in wet environments, and it’s simple to clean—just wipe with a damp rag.
Product Specs
- Dimensions: 10 inches long by 20.75 inches wide
- Temperature range: 68 to 108 degrees Fahrenheit
- Waterproof rating: IP67 waterproof
Pros
- Adjustable thermometer probe is easy to use; the controller has a bright LED display
- Versatile for specific needs; mat comes in various sizes to accommodate different needs
- Surface is waterproof and easy to wipe clean to help increase longevity
Cons
- Some users report issues over time with the temperature controller display
Get the Vivosun seedling heat mat at Amazon, The Home Depot, or Wayfair.
Best Bang For The Buck
Vivohome Waterproof Seedling Heat Mat
Increase seed germination without overspending. The Vivohome seedling heat mat doesn’t come with many bells and whistles, but it raises the seed-starting medium’s temperature 10 to 20 degrees Fahrenheit above room temperature, which is usually suitable for encouraging seeds to sprout. Measuring in at 10 inches long by 20.75 inches wide, the mat is just the right size for holding a standard rectangular growing tray, and it has a water resistant IPX-4 rating.
There’s no controller with this heat mat, but users need only plug it into an outlet to start the process. The mat is made from flexible, sealed PVC plastic and features an inner layer of insulated heating wires. It wipes clean with a damp rag and rolls tightly for easy storage. It’s a great way to increase seed germination at an affordable price point.
Product Specs
- Dimensions: 10 inches long by 20.75 inches wide
- Temperature range: 10 to 20 degrees Fahrenheit above the ambient temperature
- Waterproof rating: IPX-4 water-resistant
Pros
- Relatively affordable compared to similar options, without sacrificing additional features
- Rolls up and stores away easily when not in use—great if users have several mats
- Suitable for propagating most types of seeds, so a good choice for most gardeners
Cons
- Temperature controller sold separately
- May not be suitable for specific plants
Get the Vivohome seedling heat mat at Amazon.
Best Large Size
iPower Carbon Film Seedling Heat Mat
Those aiming to start multiple trays of seedlings indoors need look no further than the iPower seedling heat mat. It measures a beefy 48 inches long by 20.75 inches wide, which will accommodate four standard grow trays placed side by side. The mat will raise the temperature of the growing medium 10 to 20 degrees Fahrenheit above room temperature.
The mat features a supple PVC plastic outer layer with an inner layer of iPower carbon heating film. The iPower mat is IP67 waterproof but doesn’t include a controller as standard (shoppers can add a controller to the bundle if desired). Plug the mat into a household outlet to start heating and unplug it to turn it off. The large mat is also versatile—users can place it under fermenting kombucha, yogurt, or beer.
Product Specs
- Dimensions: 48 inches long by 20.75 inches wide
- Temperature range: 10 to 20 degrees Fahrenheit above the ambient temperature
- Waterproof rating: IP67 waterproof
Pros
- Available in multiple sizes to suit a variety of spaces, from narrow windowsills to large tables
- More affordable price point compared to other brands, especially considering the larger size
- Easy to set up and use—simply plug in and germinate!—and easy to clean
Cons
- Temperature may not stay constant across the entire pad; not ideal when an even temperature is vital
Get the iPower seedling heat mat at Amazon.
Best Starter Kit
Super Sprouter Premium Propagation Kit with Heat Mat
For an all-inclusive seed starting kit, consider the Super Sprouter Premium Propagation Kit, which comes with a seedling heat mat, a plastic grow tray, and a large clear dome that covers seedlings until they reach 7 inches high. The kit also includes a grow light that will provide the light seedlings need until they’re ready to be transplanted outdoors. The Super Sprouter can help sprout seeds in homes that lack a sunny window in which to place the seedlings once they sprout.
The flexible heating mat measures 10 inches long by 20 inches wide, is IXP-rated for water resistance, and it turns on by plugging the cord into an outlet—no controller is included. The plastic grow tray is also 10 inches by 20 inches, and it can hold growing medium, peat moss grow pellets, or plastic growing containers. The heating mat raises the growing medium’s temperature 10 to 20 degrees above room temperature. The dome, made of durable clear plastic, supports a T5 fluorescent light tube in its center (included); its function is to retain humidity and reduce watering needs.
Product Specs
- Dimensions: 10 inches long by 20 inches wide
- Temperature range: Between 65 and 72 degrees Fahrenheit
- Waterproof rating: Unspecified
Pros
- This full kit comes with everything needed to start germinating seeds
- Plastic dome retains humidity to help promote plant growth
- Great as a gift for beginner growers looking to learn more about plants
Cons
- Lack of thermostat can make it difficult to control temperatures for more sensitive seedlings
Get the Super Sprouter seedling heat mat at Amazon or Lowe’s.
Best Mat Set
Propagate Pro Wrap Around Heating Pad Strip
At just 3 inches wide, the pair of windowsill heat mats in this set make it possible to start seeds below a window. Each mat increases the growing medium’s temperature 10 to 20 degrees Fahrenheit, and a single controller allows the user to select the desired temperature for each mat individually. The mats are 20 inches long by 3 inches wide and can also be used on a countertop or a table if desired.
Thanks to their dimensions, these strip-style mats are also suitable for wrapping around containers of fermenting kombucha or home brew to speed fermentation. Buyers will also receive a color-coded fermentation thermometer strip.
Product Specs
- Dimensions: 20 inches long by 3 inches wide
- Temperature range: 10 to 20 degrees Fahrenheit above the ambient temperature
- Waterproof rating: Unspecified
Pros
- Thin strips are ideal for wrapping around containers such as kombucha jars
- Can be used for fermentation projects as well as for seedlings
- Included thermostat is easy to read and operate, and there’s also a convenient hanging hook
Cons
- Quite pricey compared to other options, especially considering the smaller size
Get the Propagate Pro seedling heat strips at Amazon.
Best with Thermostat
BN-LINK Seedling Heat Mat With Digital Thermostat
While most seedling heat mats are quite similar, certain aspects can make one brand stand out from another. For users who require more temperature control—when growing more temperamental plants, for example—a thermostat is a must-have. This heating pad from BN-LINK boasts a built-in thermostat that can be set between 68 to 86 degrees Fahrenheit, which is the ideal temperature range for most plants.
This pad is a generous 10 inches long by 20.75 inches wide, but there are also other sizes available for shoppers looking for something either bigger or more compact. When not in use, it can be rolled up to easily store away, and the IP67-rated waterproof surface can be simply wiped clean as needed.
Product Specs
- Dimensions: 10 inches long by 20.75 inches wide
- Temperature range: 68 to 86 degrees Fahrenheit
- Waterproof rating: IP67 waterproof
Pros
- Waterproof and very easy to clean just with a quick wipe
- Available in multiple sizes to suit many users and can roll up for compact storage
- Adjustable temperature controls can help users grow most plants
Cons
- Some users report poor heat distribution across the entire map; some cold spots
Get the BN-LINK seedling heat mat at Amazon.
Best for Rooting Cuttings
AC Infinity Suncore Dual Waterproof Seedling Mats
Much like seedlings, cuttings are more likely to grow roots when they’re provided the right temperature range. This heat mat from AC Infinity could be the ideal solution for shoppers looking to root cuttings on a bigger scale, since it comes with two large mats, each measuring 10 inches long by 20.75 inches wide. Plus, each mat comes with a temperature dial for easy control.
In terms of build quality, the AC Infinity stands out with its flexible quad-layer PVC construction that is sturdy enough to withstand frequent use. It is IP67 waterproof and easy to wipe clean.
Product Specs
- Dimensions: 10 inches long by 20.75 inches wide
- Temperature range: 80 to 87 degrees Fahrenheit
- Waterproof rating: IP67 waterproof
Pros
- Thermostat is very easy to use with its user-friendly dial design
- Comes with 2 mats at an affordable price; great when shopping for large projects
- Made using high-quality PVC layering that resists wear and tear
Cons
- Thermostat dials don’t show any temperatures, just low, medium, or high
Get the AC Infinity heat mat at Amazon.
Jump to Our Top Picks
What to Consider When Choosing the Best Seedling Heat Mats
Raising a growing medium’s temperature up to 75 to 85 degrees Fahrenheit helps trigger germination for many common seeds such as tomato, squash, basil, and other varieties. In most homes, however, room temperature is usually 68 to 72 degrees Fahrenheit. A standard heating pad—the kind for sore muscles—isn’t recommended because it could get too hot and keep the seeds from sprouting.
In addition, heating pads for the human body are not designed to withstand the moisture that often accompanies seed starting. A seedling heat mat is the best option, both for safety and for growing success.
Type
Seedling heat mats are available in two main types: solitary flat mats and mats included in a more extensive growing system that provides a humid environment. Either type is suitable for starting seeds.
- Flat mats: For many, placing a flat seedling heat mat beneath a plastic grow tray filled with seed-starting medium and just-planted seeds is practical and cost-efficient. A single mat is not expensive, depending on its size and accessories, and it will raise the temperature of the growing medium by about 10 to 20 degrees Fahrenheit.
- Growing system: For those wanting a more inclusive approach, heat mats are also available as part of grow kits that feature humidity domes. The domes keep the medium and new seedlings moist and protected. Expect to pay about twice as much for an inclusive grow kit that comes with a heating mat and a humidity dome.
Material
Today’s seedling heat mats are designed to resist spills, surface moisture, and the high humidity levels associated with starting seeds and growing seedlings. The mats feature multiple layers of flexible waterproof plastic or PVC that encase heating wires or heat-conducting film. The outer layer is sealed to protect the internal heating elements. The mats are easy to wipe clean with just a damp cloth and will resist rusting and corrosion.
Dimensions
Seedling heat mats come in a variety of sizes, with the most common being 10 inches by 20 inches, which corresponds with the size of a standard plastic growing tray. Indoor gardeners who want to heat additional seed trays can find a larger size—20 inches by 48 inches—which is sufficient for holding four standard grow trays side by side.
While those are the most common sizes, other sizes are available. For example, some come in long roll-out mats for heating many trays or in narrow strips designed to fit on a windowsill.
Waterproof Rating
Seedling heat mats are either water resistant or waterproof and bear associated ratings. For most indoor seed starting projects, either type is suitable.
- IPX4: A seedling heat mat that bears an IPX4 rating indicates that the mat is water resistant and will withstand sprays of water, spills, and splashes without damage. It is not, however, designed to be fully submerged beneath the water.
- IP67: A mat with an IP67 rating is fully waterproof, and it has been tested to continue functioning even after being submerged underwater for 30 minutes.
Temperature Range and Controller
Unlike standard heating pads used to soothe sore muscles, seedling heat mats don’t get hot. Most heat pads will maintain a temperature between 75 and 85 degrees Fahrenheit, although some can maintain temperatures of around 90 degrees Fahrenheit.
Some heating mats come with controllers, while others turn on when they’re plugged in and must be unplugged to turn off. A controller, while handy, isn’t essential for most home seed starting. Controllers differ in function: Some allow the user to choose an exact temperature, while others offer heat levels such as high, medium, and low. Still others come with attached soil probes that measure the growing medium’s exact temperature.
Flexibility
Typically, gardeners store their seedling mats once the seeds sprout, but the mats can be beneficial for other projects as well. For example, they can supply the gentle heat necessary for fermenting kombucha, yogurt, or even for brewing beer.
Pet owners can also slip a seedling heat mat under a blanket or a towel to warm up a pet bed. The supple nature of seedling heat mats makes them easy to store as well—simply roll up the mat and wrap the cord around it. When it’s time to start seeds again, it will roll out easily and perform its task.
Additional Features
Seedling heat mats don’t come with many bells and whistles, but some feature an auto-shutoff mode that turns off the heat after a predetermined time, while others can be programmed to turn the mat on and off to mimic cyclical heat changes that occur in nature.
A few mats come with storage bags. Others boast insulating pads that can go between the mat and the grow tray to reduce heat transfer by about 5 degrees Fahrenheit.
FAQs
Starting seeds indoors to later transplant to a garden or pots is growing in popularity, and seedling heat mats speed the process. Still, new gardeners will likely have a few questions.
Q. What is the right size for a seedling heat mat?
For starting seeds in a standard grow tray, purchase a seedling heat mat that’s 10 inches wide by 20 inches long. For starting seeds in multiple trays, consider a 20-inch by 48-inch mat. If only a windowsill is available, purchase a windowsill mat that measures approximately 3 inches wide by 20 inches long.
Q. What soil temperature is needed for seeds to germinate well?
Read the back of the seed packet. Most annual flowers, herbs, and vegetable seeds need temperatures between 75 and 85 degrees Fahrenheit to sprout.
Q. What type of growing medium should be used for germination?
A soilless seed-starting medium or sterile potting soil are the best options for encouraging germination. These formulations are germ-free and contain various ingredients such as peat moss, perlite, and coconut coir. Avoid starting seeds in garden soil, which can contain contaminants.
Q. When should seedlings be removed from the heat mat?
They should be removed as soon as they sprout. Often, even if only a handful of seeds sprout, the others will sprout after the grow tray is removed from the heat because they already have benefited from the added warmth.
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