Save your money and effort. Just plant the spinach. It will be fine. Spinach is a very hardy plant. Inside a greenhouse, it will over-winter just fine. I don't know where you live, that would be nice to know. We have had lows in the upper teens already this year and the spinach has never tasted better. This is my 4th year of overwintering produce.

I have over 800 square feet of Spinach in one of my high tunnels. I will harvest it and let it grow all winter long. These were taken several weeks ago. Just don't look at the weeds!

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Another problem with the heat may actually get it too hot and cause it to bolt.

Jay

I live in zone 6, close to Springfield,MO. So I dont need fluorescent lights to promote growth. My greenhouse is small 10x10. It is insulated though and I use the heavy duty swimming pool cover material as insulation. I actually did plan on just making some raised beds in long planter boxes inside. So when should I transplant the spinach to the beds. Its around 10 days old right now. Should I heat the house at all? Any tips or knowledge would be helpful. thanks

To be perfectly honest, your spinach should have been planted in October in order to harvest during the winter. When the sun is out less than 10 hours a day, plants don't grow a lot. They grow some, just at a reduced rate. You can help your plants along by having the lights come on in the late afternoon/early evening and have them run for a few more hours. That would help with growth. If you want to be able to harvest this spinach in the next 30-45 days, you may have to add a little heat and more light.

Check out the link below. It is about growing spinach in a high tunnel. This trial was conducted near Kansas City.

Jay

Here is a link that might be useful: High tunnels and spinach planting dates

I'm with Jay... save your money.

Yes, the spinnach will slow but you just plant enough to give you the amount you want. Off a dozen plants I was harvesting once a week.

The best part is, I think Jay is right that winter grown spinnach is the BEST tasting! Very sweet and none of the bitterness!

ok I am a beginner with all of this , I planted from seed my spinach and it's spring headed into summer for west texas. It seems to be growing very slow and yes it is in a greenhouse. So i planted wrong time? Do I just keep watering and it will take off in winter?