Senior Member
Posts: 293
Joined: Mon Mar 05, 2012 2:04 pm
Location: Decatur, IL

Too much heat?

Again, here is what I have already started Well I have shasta daisies, columbine, delphiniums, black eyed susans and white cone flowers started.

I'll be doing some of my veggies this weekend (broccoli, cauliflower, egg plant) and then a few others in 2 weeks (peppers, tom). What is the best temperature in the greenhouse for these kinds of things?

I have 2 40 watt lights clipped under my trays (cheaper than buying one of those heating mats). I put my indoor/outdoor thermometer in there last night pretty on top of my tray. It read 75 degrees when I got up this morning.

My little set up tends to fluctuate from 68-75.

Greener Thumb
Posts: 755
Joined: Sun Jan 29, 2012 6:26 pm
Location: paradise,ca

I kept my temp at 73 to 75 for all my stuff. The cold weather stuff like cabbage,broccoli and stuff do need to be as hot to start. The packets should tell you also.

Super Green Thumb
Posts: 2437
Joined: Mon Nov 15, 2010 10:31 pm
Location: Latrobe Pa.

My temps go from 40 to 80 every day and it does not hurt anything. I think the main thing is that you get alot of natural light on the seedlings and keep them from drying out! I have all kinds of seeds emerging every day with those temps!

Greener Thumb
Posts: 735
Joined: Mon Aug 02, 2010 2:40 am
Location: Ohio, Zone 5

Your temperatures are good. Keeping it warm enough is not a problem for me since my greenhouse is heated, but keeping it cool certainly is once temps outside climb and the sun shines. Last spring not a problem!
Excess heat really does stress out plants.
Don't know what your set up is like , but keep mild air movement to prevent problems. For mine temps don't go below 60's, preferably 65at nite, but I raise some cold-sensitive flowers. Mid 70's day temp.
Of course if it's 85 or 90 put that's another story.
Sounds like you're doing well and having fun !
It's a learning experience :)

User avatar
Posts: 29625
Joined: Thu May 01, 2008 7:21 pm
Location: Zone 6, NJ (3/M)4/E ~ 10/M(11/B)

Check in seed catalogs/websites like Johnny's, Territorial, Stokes, etc. for appropriate germination temperatures for each kind of plant. Its a good idea to do this BEFORE sowing seeds because you don't want to group the wrong ones together in a same tray.

Cole crops germinate in 2-3 days at 72-75° but need to be transferred to suitably cooler growing temperatures after germinating. Some seeds won't sprout in soil temps below 50° or 60° and peppers and eggplants take forever to sprout unless you start with soil temp at least mid-upper 70's; yet others won't sprout when temperature is too high for them, etc.

Super Green Thumb
Posts: 2437
Joined: Mon Nov 15, 2010 10:31 pm
Location: Latrobe Pa.

The high temp can also be solved some by adding 50 gallon drums of water since they stay colder than the actual temp. A fan blowing o the drums when the temp gets too high works for over heat as well as extra heat in a unheated greenhouse. My greenhouse is not heated but maitains temp above 35 all winter! My heat chambet is heated some and stays above 40 even on the coldest days and my seedlings have come up fine so far.

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Cool Member
Posts: 75
Joined: Wed Feb 22, 2012 8:23 pm
Location: Utah, USA

I stopped putting my seeds starts on a heat mat. I now just let them germinate under my lights. We turn our heat down at night and I think this helps.

By the time I start my tomaties and peppers in March and April the weather is warmer.

My cabbage and broccoli are up and I am getting spring fever.

Full Member
Posts: 13
Joined: Fri Aug 05, 2011 10:36 am
Location: idaho

my greenhouse sits over my heater vent. heat varies between 70-105 degrees. seems to be working. the heat above 90 cools down pretty fast. it;s workign so far.

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Green Thumb
Posts: 425
Joined: Tue Jan 25, 2011 2:17 pm
Location: Rhode Island - USA (6B)

I germinate my pepper seeds between 80 and 85 with a heat mat and heat mat thermometer - works well.

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