Photo by Melody
It's time now to VOTE in our 14th annual photo contest! Voting ends November 7, so be sure to cast your votes for your favorites in each category here. Good luck to all contestants!

Seed Starting 101: Seedling Heat Mats and Inexpensive Alternatives

By Jill M. Nicolaus (critterologistJanuary 29, 2010
bookmark

Are your peppers more poky than perky? Is your basil more balky than bouncy? Do you wish your seeds would speedily sprout into sturdy seedlings? Bottom heat could be the answer. The seed catalogs piling up by your easy chair tout the wonders of seedling heat mats and they are right! Heat mats can produce remarkable results. But are they the only answer?

Gardening picture

(Editor's Note:  This article was originally published on January 24, 2008)

For some types of seed, warmer temperatures are critical to germination. I successfully used the warmth from my oven light one winter to germinate two precious seeds of Vigna caracalla (Snail or Corkscrew Vine). While carefully monitoring and adjusting the temperature by propping open the oven door just so with a folded towel, I made up my mind: I wanted a snail vine bloomseedling heat mat!

I ordered two heat mats and a temperature controller a couple of years ago. I love them! Seeds all but leap out of the seed starting trays in half the time it previously took. My seedlings look so much stockier and healthier when it's time to plant them out. Although there are DIY alternatives to "real" seedling heat mats, I fell for the appeal of something I could unpack, plug in, and put to work right away.

heat mat & controller closeupSeedling heat mats are usually sized to hold one, two, or four of the 1020 size standard nursery flats. You can plug multiple mats into a typical thermostat controller (check specifications for max wattage). [1]

Why get a controller? Seedling heat mats typically raise the temperature of your flats or pots 10 to 20°F above ambientheat mat controller (room) temperature. My basement occasionally warms to over 70°F on a sunny day, and a 20°F rise in temperature on top of that could mean the death of my seeds. A controller to maintain the temperature at an even 78°F seemed like a good investment.

If the prices on seedling heat mats and controllers make you wince, there are some DIY alternatives. You can supply some bottom heat simply by putting your seed flat on top of the refrigerator, television, or other warm spot. A 40 watt incandescent bulb positioned just under a metal shelf makes a good heat source for a seed pots placed on the shelf.

You can also construct a light box, an enclosed space warmed by one or more incandescent bulbs. If you don't want to wire your own sockets, you can use a pot light, desk lamp, or clamp-mounted fixture. Make sure to keep wiring away8 week pepper plant from possible wet areas, and leave plenty of space around the bulb. The enclosed space can be as simple as a shelf of your existing light stand, wrapped in plastic sheeting with front flaps to allow easy access.

Monitor the temperature inside your light box to figure out what wattage bulb(s) will give you even heat of 75 to 80°F. Putting a thermometer into a pot of moist potting mix will let you monitor actual soil temperature. If you are comfortable with wiring projects, you can install a thermostatic switch to turn the lights on and off as needed.

Heat cables are often much less expensive than seedling heat mats, especially for larger numbers of seedling flats. They are designed to be buried in flats of sand or gravel, with the flats of seedlings placed on top of the material for even heat distribution. A similar DIY bottom heater option uses lengths of Christmas rope light (not LEDs), buried in clean kitty litter. The amount of heat basil seedlingsprovided is regulated by the length of rope light. [2]

What about that old electric blanket? No! Electric blankets and household heating pads are not designed for use 24/7 and are not for use in potentially wet environments. All those safety warnings are on them for good reason. Even if you have been using one under your seedlings for years without burning down the house, please consider a safer alternative.

Whether you choose to use an "official" seedling heat mat or a DIY alternative, please be safe. This isn't the time to just throw something together and see if it works. Use heavy duty grounded extension cords and GFI outlets. Get expert advice if you hatomato seedlingsve any questions

How long should seedlings stay on the heat mat? In my experience, pepper and basil seedlings benefit from a couple of weeks on a seedling heat mat, but after up-potting they do just as well on an unheated shelf in my 60-70°F basement. Tomato seedlings sprout almost overnight on a heat mat but must be removed from the heat after the first sign of germination, or they will become very leggy.

Germination instructions for many seeds recommend growing on the seedlings at a cooler temperature once they have sprouted. Since most seedlings won't need to stay on the heat mat long, a single heat mat can help start enough seeds to fill dozens of flats. See Tom Clothier's germination database for temperature requirements of many types of seeds. Torenia seedlingsSeeds that need a warm start (70°F more) all seem to do well for me when I set my heat mat controller to 78°F.

Start with plants that appreciate a longer head start. When they're ready to transplant into larger pots or cell packs, it'll be time to put the next round of seed starting trays on your heat mat. Flowers like Torenia (Wishbone Flower), Geraniums, and Wave Petunias are among the first on my sowing schedule, followed by peppers, then byTorenia blooms basil and tomatoes.

Whether you buy a seedling heat mat or put together a DIY alternative, I hope you'll consider adding extra heat to your seed starting shelf this winter. The results will amaze you!

For additional information on seed starting, see my previous article, Seed Starting 101: Setting up Light Shelves. Growing your own plants from seed can be both cost effective and fun. Nothing beats the satisfaction of cutting flowers or picking heirloom tomatoes from plants you started yourself from tiny seeds. Go, sow, grow!

 

 

[1] Thanks to Park Seeds for additional information about the seedling heat mat and thermostatic controller that they offer. They gave me good advice and assistance when I purchased mine. You can check them out in The Garden Watchdog.

[2] We've had some great discussions about heat mats and DIY alternatives on the DG Propagation Forum (subscribers only). I'd especially like to thank Heathrjoy for her contributions, including posting the link for the rope light soil heater.



  About Jill M. Nicolaus  
Jill M. NicolausBetter known as "Critter" on DG, Jill lives in Frederick, MD, where she tries to fit as many plants as possible into a suburban back yard. The birds are mobbing our feeders lately, so Sunshine Girl and I have a job keeping the Flyby Cafe' open for business! This year, we put out a special feeder just for the squirrels, filled with a seed & corn blend. We still see them acrobatically snatching food from the other feeders, but at least now they let the birds get a beak in edgewise! (Images in my articles are from my photos, unless otherwise credited.)

  Helpful links  
Share on Facebook Share on Stumbleupon

[ Mail this article | Print this article ]

» Read articles about: Gardening Tips, Propagating Plants, Seed Starting, Vegetable Gardening, Herbs

» Read more articles written by Jill M. Nicolaus

« Check out our past articles!



Discussion about this article:
SubjectTopic StarterRepliesViewsLast Post
tomato seed germination DKK 1 9 Apr 11, 2011 8:26 AM
Other methods edelseu 1 69 Feb 11, 2010 6:00 PM
heat mats for germinating seeds greenthumbstres 1 73 Feb 6, 2010 9:26 PM
heat mats curb mildew? wandygirl 3 34 Feb 5, 2010 8:49 PM
Price? Petalpants 8 119 Feb 4, 2010 4:52 PM
"proofing" setting on oven puertorico 1 27 Feb 4, 2010 4:50 PM
advice marti001 14 137 Feb 4, 2010 4:58 AM
Too hot heat mats joanlc 3 76 Feb 2, 2010 5:34 AM
My sources for cheap heat mats- mothermole 1 245 Jan 29, 2010 5:19 PM
Great article ladygardener1 3 50 Jan 29, 2010 4:00 PM
heat pads DIRTYGIRL71 2 115 Oct 24, 2009 12:10 PM
Very interesting doccat5 18 198 Oct 10, 2009 5:50 PM
Multiple heat mats woofie 7 238 Mar 6, 2009 9:10 PM
Keep reading, you just never know! Tink2U 1 109 Apr 21, 2008 10:40 PM
Cycad Palm Franki_2008 3 55 Feb 3, 2008 6:25 AM
You cannot post until you login.


We recommend Firefox
Overwhelmed? There's a lot to see here. Try starting at our homepage.

[ Home | About | Advertise | Media Kit | Mission | Featured Companies | Submit an Article | Terms of Use | Tour | Rules | Privacy Policy | Contact Us ]

Back to the top

Copyright © 2000-2014 Dave's Garden, an Internet Brands company. All Rights Reserved.
 

Hope for America