When + When NOT to Use a Heat Mat and Humidity Dome For Seed Starting
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- Опубліковано 7 лют 2025
- Heat mats and humidity domes can be a beneficial resource for seed starting, but there are specific times to use them and when not to use them. In this video we will break down the risks and benefits to using a heat mat.
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Thank you all so much for watching and Grow BIG!
Hah! I use my heat mat all year long but not necessarily for seeds. Heat mats are brilliant for encouraging sourdough starter and on bread day for the dough itself. 😊
Oh! Never thought of that!
Good tip, thanks!
Great tip! I made bread yesterday & I`ve used a heating pad from 1973 to proof bread. Now if it quits on me..I know what to use!
brilliant!
So is cooked pasta water - I always use it to make sour dough starter ...
@@Impulse_Photography Cooked pasta water…do you mean store-bought pasta or homemade pasta, made with flour & eggs etc?
I germinate my seeds in used fast food containers with lids. The lids come with flaps to open so air can escape/circulate. I adore this setup because the minute the seedling pokes up I remove the lids and water from underneath. Been doing this for a few years now with excellent results.
And it helps with the landfill issue a little! Depending on how long you use them! Good idea!
I do that too
The recent public health scare has left us with an over abundance of these plastic trays at home. We are repurposing these as well. Great idea.
Are they under grow lights.
@@Jbtpba spray paint them.
I was listening to this video today while driving and literally made a doughnut on the mainstreet to get home in time to save my seedlings from all my mistakes 🤯 - Thank you for all these informative videos!!
Yeah, I have broccoli in with all the other plants that DO need the heat mat, but they are ancient seeds that are probably not viable anyhow. If any of the 4 sprout, I'll be pleasantly delighted, LOL.
😂
I ran over and shut off the heat pads immediately. Omg! Killing w kindness. Thank you Luke!!!!!!!!
What I learned today:
1) warm weather crops prefer the heat mat and cold weather crops do not want it.
2) Don't wait until all seeds have sprouted before removing the humidity dome. Remove the dome after I see my first sprouts, otherwise I risk legginess in the stems and gray mold. [ and I have had both when growing microgreens]
Thanks! 😃
Right. The second one here has always been a big one for me. I had heard in more than one place to leave it domed until most, if not all, the seeds have sprouted.
I decided to try sowing lettuce outside in early March with snow still on the ground in a raised bed, here in Ontario, Canada zone 5b. The result was early lettuce and it didn't bolt until August. Then I saved seeds from it.
Direct method :)
Hey that's awesome! I'm in BC, zone 6b - I wonder if I should try that? My only real issue is the fact that I don't really have any place to plant them. LOL! No garden beds. Maybe next year.
I retired last year and have a renewed interest in gardening. I am so happy that I’ve found your channel. Your videos are always enlightening. I struggled last year with starting plants but with your advice hope to be more successful this year.
I always enjoy n learn new things
We retired a couple years ago right about Covid time and have gardened for over 40 years. Now it’s a complete educational new adventure. Every year’s a different challenge and education. One by one we equip ourselves with not only the skills but also the ‘armor’ against so many battles. For instance last year’s surprise battle was flea beetles. Right now I am on the homestretch with indoor fungus gnats. And there’s the powdery mildew. Finally I am understanding and being successful. Thanks to Luke and others’. And I save seeds.
retirement? LOL you must work for a city. There's not a chance a non union worker is retiring. I wish I could garden all day!
@TacoBell5DollarBox People retire all the time, daily. It doesn't matter what your job is or where you live but it does matter how much effort you put into your job to begin with. Sounds like you're the no effort type.
The best video on UA-cam about seedlings
Thanks for explaining this in layman's terms- You are a good teacher!!
Just sharing my tip. Clear plastic egg containers work really well for me. Each egg cell can be a different plant, you just need to map it on paper. Keep the top, that is your dome. After sprouting, you can spoon out the seedling for transplanting into a room temp pot without disturbing the roots. Of course this won't work with large seedlings like squash, but it is perfect for herb seeds and peppers. Depending on your mat, you may need to have a towel or 2 between the mat and egg crate. Always use boiling water to wet your soil mix, this will kill fungus gnats and mold spores. Let it cool sufficiently before you plant. I will get algae growing in cells if it is left too long, but no mold or gnats.
Won't the bowling water kill the mycorrhizae in the soil?
@@sarahmcenhill By soil mix, I mean seedling mix, it should not have any microrhyzae added. However if you only have potting soil to work with that does have it added, then I would still boil it when you are starting seeds. Yes, you will kill that too, but since you are eventually going to transplant later, you can move it into the regular potting mix later.
Eh. Just quarantine the plans from any plants you currently have going at the time and use mosquito bits in your watering regimen.
People don’t realize how important fungus is
Finally an excellent discussion on heat mats and humidity domes. I'm not aware of any other videos that discuss these dos and don'ts. That's kind of amazing when one considers the importance of this subject. Thanks!
Dude your videos through out the years have helped me grow my business. Out of all the farming channels you are my go to for detailed, yet simple to follow vids. Thanks
Dude? .....how old are you? show the man some respect. dont call him dude
@@scottboyd9383 dude, why you acting like such a little immature girl? Scott, my dude, get a grip.
@@scottboyd9383Mr. Dude, please be aware that on social media dude, chick, man and yo are all terms of respect/endearment when followed by a compliment. Bless your heart. I hope you have a great day.
@@scottboyd9383 Come on now, good sir, if you listen to yourself, you sound like a grumpy old man. If you can somehow get over your shock, read past the dude part. It's quite obvious he is paying the man the upmost respect and praise by saying he's better than all the other channels. That in fact he has helped his livelihood. It appears a few other people agree with his view and nobody else finds it offensive or disrespectful but yourself. Now good day🖖
@@scottboyd9383 Mr. Boyd! It's delightful to see a man with such manners in todays day and age. It is a rather rare occurrence. So I hereby salute you for your foolish efforts to make people of such low caliber speak like yourself. I admire you taking your time to speak to the peasants in this commentary section. They clearly should know to behave better.
*Sarcasm*
🤫
Thank you for addressing humidity domes, it was very informational. I was shocked when you didn't say, "Grow big or go home!"
Finally someone with good information on when some of the seedlings have sprouted!!
Good Afternoon from a snowy New Hampshire.
May the day find all safe and healthy.
You should do some videos on cannabis growing. The way you explain things could really help a lot of people. Growing cannabis is also becoming very popular/widely accepted/appreciated. It’s fun, and I don’t even smoke it! I just love the plant itself 😂❤ great video!
I'm glad I saw this video because I just bought a heat mat and was going to place it under my plants (lettuce, kale, broccoli, etc) and some already developed leaves.
This was so helpful! Thank you! I feel overwhelmed starting a garden because people make it complicated. But you simplify it!
I am learning so much!!!! I bought heat mats last year. Yes I used them after germination and yeah the plants were a failure, but now I understand why!! I also learned fr your viewers to use the heat mats to help my sourdough stater get going. My house is usually 65-68 degrees. I have a heck of a time. So much great information!!! ❤❤❤❤
Woke up this morning to 6 out of 20, of your Alexandria Strawberry seed,sticking their little green leaf heads up! First time trying to grow Strawberries from seed, thank you for your fantastic seeds!!!
This was super helpful. Thanks Luke!! Could you also tell us about how and when to use grow lamps and indoor greenhouses? I live in Utah so it’s dry and cold here. This is my first year starting my garden all from seed.
thank you for explaining how to use domes. i never use heat mats, but I can see where I've gone wrong with the domes. I used to leave them until my seedling tomatoes touched the top. Oppps. The only way I have avoided fungus and such was the cinnamon I sprinkled on the soil as soon as I seeding.
This was a life saver! Or i should say flower saver! This is my first time trying to start my flowers from seed. I was going to do everything wrong! LOL! Thank you so much!
What enthusiasm you have!!
Great information, i don't have a heat mat. I use the top of my hot water tank in my furnace room and had great success with my tomatoes last year and with my sweet potatoe slips that I do the potting soil method with.
Basic household temperatures in the winter are recommended to be 68° in winter. If you have been outside where it is32° it is not only going to feel much warmer than outside that difference of 7° between 68° and 75° will save you 14-21% on your heating costs. Additionally, having indoor temperature of 72 and higher is a great incubation temperature for viruses and bacterias trapped indoors meaning you and your family will be more susceptible to becoming sick in the winter.
And then there are those sicko people like myself who prefer the temp between 55°-60° who do need the heat mats for most germination although I think I have been misusing the domes.
Love all the info.
You’re not a sicko-you’re perfect. Married? 😆
I too keep it very cool. If it were practical, I’d keep it that way year round.
@@jackjohnson291 not married but probably way too old.😘
But hey, if you have good night vision and can do chores on a ladder without getting dizzy you could be pretty perfect yourself.
I'm 53 and barely learning how to grow my own food. Thanks for all these very useful tips.
TY!!!!! I have such a hard time with this.
Boy did I need this video the last 2 years 😅
Thanks, Luke!
I can literally tell you're a father now. Love it. You've taught me and my children a lot.
I use those carry out containers to start plants, too. Those large trays haven't worked well for me. I got the idea from Growing a Greener World, Craig, the tomato expert, who starts many seeds in small trays and moves them to 3 inch pots. His name is Craig, so why wouldn't I listen? There is one container I liked but could not use, and that is the rotisserie chicken container from Costco. Even though it seemed like a mini greenhouse, plants did not grow in it. I don't know why, but it's back to the recycling bin. There is one more thing I figured out. When moving from the start container to the 3" pots, I use a small plastic fork to carefully dig the seedlings, which avoids root damage and I use a plastic spoon to press the soil evenly around each transplant. I get the best seed growth this way using heat pads, and when the first ones sprout, I turn off the pads, and they keep on growing and sprouting. Thanks again, Luke, and may the Lord bless you and yours.
Very informative!Thanking you for saving my seedlings in zone 5.
Thanks so much for explaining this so thoroughly Luke, your videos have taught me so much!! I've been trying for years with very limited success to start from seed indoors. This helps. I haw a feeling its going to be a good year in my garden!
I definitely like my heat mat and humidity domes. My seed starting took off once I added in the heat mat. My peppers (especially), watermelons, squashes, etc. definitely have to have it, my tomatoes and a few other summer veggies like it pretty well. I use the dome for most things, but not peppers, because they don't like "wet feet". Plus my grow table is in a pretty dry spot of our little house. Great info Luke as always!
Yes! I’m getting Spring Fever 🤣🤣 Thanks for this Luke. Now I know what I did wrong last year. I didn’t take the heat mat away.
I just re-watched this for information about using the heat mat for my onion seeds. I love being able to watch this great information whenever i need it. Thanks!😊
I've watched this 3x now. Did he say to use it for onions? I don't know what to do!
@@nanaof6babiesuse a heat mat for warm weather crops, and don’t use it for cold weather crops.
i was just thinking i needed a mentor because my plants were leggy. thank you teacher 💕👌
Thanks for the tips michiFAM! We are just starting to grow veggies and herbs indoors! 🙌💚
Thanks for the detailed video. It answered a lot of my questions
I was wondering why I was getting really good initial sprouting then everything started stalling or going backwards.. things started dying or looking unhappy... because I was keeping everything on the heat mats and under humidity domes! Now I know better!
That was useful information. Now when is a grow light necessary and not?
Thanks for the tips I started my seedlings ang excited to for them to grow.
I germinated my pepper seeds in a closet. I put the light right over the tray. I set my heat mat to 85F and it never turned on because the net temperature was already 85 because of the room temperature + heat from the light! Sometimes it really not necessary.
What is this florida? Canada 🇨🇦 we do it different. A 40 watt lightbulb in a storage container warms the lid, which is now a heat mat.
Considering the on and off weather in my region, I thought I was playing it safe with having the seeding mat set up in my basement. But thanks to this video, I *might* be able to save my seedlings before it's too late. I'm using the cheaper mats (which ran for 20 bucks so I can't be too mad there) which have no dial/settings. They work well!.. _too_ well. And without domes on my current trays I had no way to control humidity outside of watering them heavily.
Welp, hopefully these seeds germinate before I have to spend more dosh on trays. Thanks again for being super knowledgeable Mlgardener! I've been gardening for years, but even some of the simple methods can be a bit of a challenge to tackle.
Good information. We have been wintersowing in milkjugs in our breezeway for a couple of years. We also got a tiny grow light to grow a few tomatoes inside. Can't wait to see it with grow light.
Oh man! This is what I was searching for when I started my seeds. I couldn’t find this info anywhere and so I just did the wrong thing 😂 I didn’t use a heat mat but I totally used the dome WAY too long. So far everything is still alive but I’m afraid I will start seeing them die off. Hopefully I didn’t damage them too badly!
This is so helpful. I started a practice run with my seed starting kit / LED and they all came out leggy and died. I left the dome on waaaaaay too long and didn’t water them. 🤭😭
I use them for seeds and for some houseplants that love tons of warmth to express variegation (eg paraiso verde)
Thank You so much!! Great information!! I'm a beginner gardener in San Diego!!
Thanks Luke great information I now know why different seedlings 🌱 didn't do well with my Domes n Heating Mat in the past .Took notes and will definitely try your suggestions 😉
Thank you for the informative video. Total noob here, I may or may not have run into the next room over to shut off my heating mat lol.
this is exactly the info i needed. % humidity clarified many things. would love a similar vid on propagation. :)
Thank you! Good tips!
When I had to germinate seeds in my cool basement, the heat mat helped, but now that I germinate them in my kitchen at ~68 degrees, I don't need it. I might use it for peppers and eggplant if I have it around.
I did exactly what u said for the braccias and they are supper leggy! What now
Just placed my first seed order with your store. Can’t wait for them to arrive.
Thank you, just planted my first round of seeds today and wasn't sure about the humidity dome.
Thank you Luke for making all this videos with all this good information.
i'm so glad I came across this video. I'm just starting to grow my own seeds for the first time. I bought a humidity dome. I just started seeing kale and lettuce and put the dome on even though they sprouted two days ago. I probably should not have planted peppers in the same cells because I now understand they need help with heating mat, while lettuce and kale will not. UGH. Anyway, great video and now I will not be using dome since seeds have sprouted. Thank you!
Granted I use smaller trays (lettuce containers/takeout/etc) covered in plastic wrap but I put them on top of my coffee pot and it cuts germination time in half. Once they germinate, I uncover them and stick them under shop lights. Works great for me.
Fantastic information! One question….if using a heat mat in an unheated area to help keep soil temps warmer….can you leave it on after seed sprouts? And by leave it on I mean use a thermostat set at maybe 60F.
Thank you Luke. I started my brassicas indoors and did exactly the opposite of what you said to do. This is my first time starting indoors and I'm a rookie, so you were absolutely right. I've got a ton of leggy cabbage, bok choy and broccoli. Oh well, I'm going to get them in the ground on Monday because we will be past a frost tonight and tomorrow. I hope they make it until Monday! Thanks again for your great teaching. (And your seeds!)
If I may, two questions. My seeds are started on a wire shelving unit. Should I line the shelves with foil under the heat mat and the trays holding the cells? And how do you label the cells when using a humidity dome? My labels don't fit under the lid and I water from the bottom and they move. I buy your seeds almost exclusively and I'm going to start your trifecta+ on our homestead gardens. Thanks Luke!
Thank you so much for the amazing teaching videos!! You are a great teacher & big help!! Blessings to you from Kentucky 🙌🏻🦋🙌🏻
Thanks for you video! My husband & I conflict on when to use a humidity dome. But then I do use Heat mats right now with some of my seedlings on cold nights because I am growing in my Unheated Greenhouse. So only on the cold nights and then 1st thing in the morning at 5:30am I turn them off and check if I need to water them Also my Heat Mats only heat up to 10 degrees above the ombieny temperature, so I hope that is OK.
Thanks again for all your videos. I have been following you for years.
In 10 years of seed starting I've never been able to use humidity domes under grow lights. Mold, the fatal kiss of death, LOL. I'm cursed with having to check and water frequently instead. Thanks for the advice on the heat mats. I'll stop leaving them on too long after the summer veg seeds sprout.
I’ve lost so many plants before I learned this (the hard way) years back. I still love them and use them, even though I have a greenhouse space now. Another way I lost a lot of plants was by not knowing how to bottom water properly. Which is another video suggestion for you.
Another great video! Really appreciating this seed starting series. Keep up the good work!
Most everything i see says to prop up the dome until most have germinated, which i have always done. Often for several days, especially for peppers, because they tend to germinate randomly. This year i will try taking the dome and heat mat off earlier than i normally do. And maybe turn the heat mat lower for my peppers and tomatoes. I typically have the thermostat set 82 for those and they pop up in like 4 or 5 days. Maybe i will set them more at 77, 78?
Second year grower and yeah I left the mat and humidity domes on too long. Also had the green mold on top of the soil from too much moisture, every rookie mistake made. I know that improper lighting technique can cause legginess but I wonder if too long on the mat also contributed to the lengthy gams I ended up with. Not a total seed-starting failure but lost quite a few by not being more careful. Just starting up again in the PNW, thanks for the timely tips Luke.
I just did the same thing last week. Now all of my brassicas are leggy and falling over. So now the heat mat and humidity domes are off and Monday, I'll transplant them outside. What a goof ball I am! rookie mistakes like you said :)
How to prevent the green mold on top
@@sweettalk9200 maybe don't allow it to be wet so much allow it to air off some to touch
So glad this came across my feed as I would have messed up my seedlings I just sowed!
Heat mats for starting peppers, tomatoes, eggplants, basil and sone other herbs and flowers. but once they are germinated and I move them. I also use them for growing ginger and tumeric .
Can't wait to put my plants in the ground thank you for all your valuable information
I use the proofing setting for the oven and keep them warm until sprouting.
Thank you for all the information. I was worried about buying meds and how I was going to afford them. Good to know there’s just a few seeds. I actually need them also all the information on the plastic domes. Makes perfect sense that it could cause mold and then the lack of air.
These are exactly the answers that I have been looking for! You explain everything so well!
When would you recommend taking your seeds off the heat mat in the case that only a couple have sprouted? I have parsley currently germinating and only 3 have fully sprouted but planted 20+ seeds. Would you recommend just taking them off the heat mat now that sprouting has begun and let the other seeds germinate slower without the extra heat?
Garden Answer suggests using vermiculite to cover seed starts to keep the seedling from molding.
Best video/info I have found in this topic! THANK YOU!
Question: I live in Colorado...dry climate. I grow microgreens on coconut coir mats in a cheap mini-greenhouse in my family room. In the past I've used heat mats until the seeds sprout, have grow lights on each shelf, and have a small desk fan blowing over 12 hours a day. My question is: I've never grown broccoli microgreens/baby greens, so will they benefit from a cooler environment since they are a cooler weather crop? Ty for your VERY informative videos. Even at 67 years old, I'm learning lots from them!
They do! Cooler temperatures
Yes, no need for heat mat for cooler temp crops. Heat loving plants benefit the most from a heat mat: tomatoes, peppers, eggplants and some herbs. For most micro greens, you likely don’t need a heat mat at all unless you are growing them in a really cool area of your home (such as a room you don’t spend a lot of time in and keep the heat down really low).
Thank you so much, totally clarified alot for me and the second heat mat I was going to buy- won't be ordered.
Perfect timing, as usual. We are starting seeds here, too. I have killed sprouts with the heat mat as well as the humidity dome. Both were due to me using them for too long. The heat mat completely dried out my soil overnight. The dome has caused dampening off and mold issues. Now I only use them in winter, only in conjunction with each other, and only until the first seeds sprout.
Funny that I spent at least a couple of hours yesterday researching when to remove the dome, lol. Second year gardening and I'm still learning some of the basics.
Also, the MIgardener cover crop is working great over wintering my raised bed. So nice to see it full of life instead of just sitting there fallow.
Thank You for this video, I was so stressed I didn't buy a heat mat.
Thank you Luke! I needed this today.
I use heat mats with temp probe for growing tomatoes and peppers with good results in my garage in northern Ohio.
I don’t have the indoor space for my starts.
Luke , what causes seeds not to sprout?. Its new seeds that I just bought and I am using a seed mix . Thanks again!
thank you. I have wondered about the dome..
If I start seeds (cracked with tiny tail) in water/paper towel (anything that precedes the dirt & tray) and then put them in the dirt & tray am I still in that part where I apply heat & dome or do I skip the heat part entirely (it's germinated) and just keep the dome until they break the surface?
These are questions that have me up at night
Thank you so much. I really needed this video.
Last year I had a lot of difficulty with germination rate, so I picked up a heat mat/thermostat kit and humidity dome, and this year it was like magic. Everything sprouted quickly. But I also got white mold and now I know I need to put that stuff away quickly after sprouting.
Luke @MIGardner
When the seeds begin to geminate should we remove the tray from the heat mat as well as removing the humidity dome?
I know to remove the heat dome when seeds begin to sprout but do you remove the heat mat when all seed are sprouted or when you see just a few seedlings?
when a few have sprouted, the heat mat comes off too.
@@MIgardener thanks
Do you have to use the humidity dome if using an indoor greenhouse shelf? I have heat mats but am not using the domes currently.
I was definitely looking forward to this video! Thank you! Help with the heat mat info was needed, and the humidity dome info was reinforced. Great to know about the ‘garage’ temp too.
I keep asking you if my garage is still below 50-40 degrees. Should I keep tomatoes, peppers and cucumbers plants on a heat pad. Because I think my garage is still too cold for these plants
You really have a good method of teaching us!!! Thanks
Great video! I’m also looking forward to learning more about the use of your new greenhouse.
Using dome in garage, if it’s still very cold in there. If I am growing cucumbers, tomato plants and other warm plants. As soon as you see one or seedlings coming up. Should you take the dome off, even if they are different seedlings
great video I'm a beginner gardner I got seeds from migardner planted onions and had great germination but after a few days they started to die when do we use a grow light?
Just subscribed. Your videos are great; so informative and full of common sense. I’m newly retired and want to branch out into vegetables this year instead of just flowers. I wasn’t sure about the heat mat and humidity dome and I don’t really think I need them. Thank you!
Thank you Luke. This video was so timely for me. You answered several questions I had as I'm starting my spring garden.