Lerway heat mats (also called a seedling mat or heat pad), keep seedlings, cuttings and cold-sensitive plants toasty warm and growing even when the temperature drops. Great to have on hand for a little plant-life-saving too, for drying over-watered plants out faster to help prevent root rot, and to help roots recover after repotting or root damage.

These mats are water-resistant, thick and sturdy, providing a good solid base under your pots, seedling trays or grow house, yet still flexible enough to roll up and store away when needed. At just 21 watts they are very low on power consumption (running a heat mat for 8 hours a day, 7 days a week averages 5 cents a day or $4.51 to run for 3 months right through winter*).

Temperature

Most seedlings germinate best with a soil temperature around 25 to 35 degrees, and for most plants, roots grow best with a soil temperature of 18 to 25 degrees. Grab your Lerway heat mat (and a grow light unless you're blessed with great natural light all year), and you're good to grow right through winter. Lucky plants!

These heat mats lift the soil temperature 10 to 20 degrees above the ambient temperature. In more enclosed spaces, or with covered pots or a grow house on top, it'll maintain a warmer temperature, so if you want it to run a bit cooler, increase space and airflow.

Designed to work by themselves without a controller, however they are compatible with a heat pad controller (not included, available separately), if you prefer more exact control or want to set different daytime and night-time temperatures (which does also happen naturally if you just leave it on since the night-time ambient temperature is lower anyway). And if you don't have one already, definitely get yourself a temperature meter at the same time to keep an eye on the highs and lows (you can also change the environment to adjust the heat without a controller - tips below).

Size

The Lerway heat mat measures 52cms long x 25cms wide (the standard size for a seedling heat mat), and has a nice long 1.8 metre cord with NZ plug. It comes rolled up in a branded box as shown in the photos. 

My review (and tips for use)

I have tried the solid Egmont, flexible Cultiv8 and Inkbird Plus, and comparing those to the Lerway, I find it a bit thicker (in a good way), and a little slower to heat up than the speedy Inkbird Plus. Give your Lerway mat a good 15 to 30 minutes to gently warm up and it'll maintain your seedlings and cuttings roots at a nice toasty 10 to 20 degrees above room temperature. I also find they don't heat quite as evenly as the Inkbird Plus.
 

These pads are also a little thicker than the Inkbird and Cultiv8, so arriving rolled up in their box means you'll likely need to turn on and heat them up to flatten them out before first use (they are pretty determined to stay rolled up at first). I just popped mine on for about half an hour with a couple of heavy books on top and it was good to go.

This tip isn't only for the Lerway brand, but with both a heat mat and a grow light going, soil will dry out faster or water props evaporate faster, so you'll need to keep an eye on watering so the roots aren't left high and dry. I really like that Lerway are also water-resistant so no problem with the occasional spill, just wipe it off when you notice it.

*cost per day based on 8 hours use per day, 7 days a week, at $0.32 cents per kilowatt-hour (kWh), based on the 2023 average NZ electricity rates published by Canstar Blue