Growing in cold frames!

Here in Texas, if I wait until April (after the last frost) to set my tomato plants out, the early summer heat arrives so soon, my fruit production is reduced. If I plant out in early March, we still have a few killing frosts which require covering the seedlings at night. I usually start seed germination near the end of December and allow the plants to grow pretty large on a light table before I set them outside to harden off and plant.

This year, I plan on constructing a wood/clear plastic cold frame on one of my 4'X8' raised beds with a thermostatically controlled heater in the cold frame. I also plan on starting my germination earlier in December. My hope is to get my plants larger and to the blooming stage before planting them out after the last killing frost in early April.

I've noticed in past years that plants with a few small blooms still set fruit on the early blooms after transplanting. If you see any holes in my plans, please advise.

Ted

[rwsacto]

Hi Ted,

My experience with cold frames sez the real challenge is keeping them from overheating on sunny days. Even with an automatic thermal opener for the top and a solar powered fan, one failure to open will wipe out your early efforts.

That being said, I will use one again for winter greens.

For early tomato planting, I use WOW.

Good Luck,
Rick

[KarenO]

Big ( like 18-24 ") and already blooming seedlings is how I get around my short season and am able to grow midseason heirlooms up here. I find they do set fruit on those first blooms for me. Agree you will have to be able to open up your cold frame to avoid over heating in day time.
Karen O
I start seed mid March, move to heated small greenhouse in April grow on and then harden off to plant out end of May. I do not get huge production but enough to have too many tomatoes every year with ripe ones end of July in a good year and depending on the variety. December seeding for April planting out seems very early to me but I guess it also depends on the variety and your problem of high temps in summer is the opposite of mine which is the possibility of late and early frosts.
Hope your plan works great for you!
KO

KO

[Cole_Robbie]

You are growing plant starts in containers, right? I agree that avoiding overheating is a challenge. High temps will require frequent watering as well. I like to have plants in 1020 web flats, so I can dunk them in a larger container to water.

As far as season-pushing goes, my experience has been that even when I can get early plants to live through frosts by covering them up, nothing really happens until the ground warms up. Black plastic mulch over a nice big ridge is a proven technique that I have had good luck with to warm the early spring soil, at least when the sun will shine.

[dpurdy]

tedln,
I grow in high tunnels which is the same as what you want to do, only on a larger scale. The only issue you may have is the heater. You may have to place it outside of your raised bed within a small enclosure. I would then find a way to pipe the heat into your cold frame. Setting a heater in a space of 4'X8' you may create too much heat for the plants. You will also need the sides, or one side of the cold frame, to roll up during sunny warm days. You could set it up so that you could open up the ends of the cold frame which will allow for airflow. I always try to keep my tunnels below 90 degrees.
Last year we had lots of early Spring rains that hampered early growth in many gardens around me. What I did during this period was that I took some of my irrigation tubing and made hoops for my outside raised beds. I put a screw in one end and then bent them over to the other side of the raised bed and put a second screw in. I spaced them about two feet apart along the length of the bed. I then attached a 1/2" X 1 1/2" strip of wood down the length of the hoops, on the middle of the top. This kept all the hoops standing straight and also gave them some strenght. I used wire ties, or zip ties to hold the strip of wood in place. Pretty simple to do. You can also remove the tubing and plastic once the Spring cold and rain have passed. I used a staple gun for holding the plastic in place. I only removed my plastic this year and left the hoops in place. I plan on using it again this year. I didn't grow any tomatoes in my raised beds but it worked well for any of the plants that had in the raised beds. You should be able to put hoops and plastic on your beds for your tomatoes but you will have to remove the plastic once your tomatoes grow to the height of 2 1/2 to 3 feet tall (by this time, there shouldn't be any chance of frost). I made mine about 3 feet in height. This would be a simple way to get the head start you're looking for. I wouldn't build a wooden frame that covers your plants until their full grown. A four by eight foot enclosure would create too much heat and too much work for what you're trying to do. By enclosing your raised bed with the plastic you should also raise the temp of your soil much earlier. I live in the northeast and last year I was harvesting tomatoes by the end of June. With some heat as protection, you may be able to plant up to a month earlier than normal. Good luck with your project. I hope your successful.
dpurdy

Thanks dpurdy!

I've also used low tunnels over my raised beds with good results. I used 1/2" pvc hoops bent over the beds with each end inserted into short 3/4" pvc tubes mounted at bed height. It made it much easier to remove the hoops when hot weather arrives.

I don't plan on using the hoop system this year, but will simply construct a temporary wood frame with clear plastic overlay as a cold frame. The front and top of the frame will be constructed of repurposed screen doors covered with plastic. The front and top can be removed by simply removing a couple of bungee cords holding them on. I plan on using a small under the desk heater fan with a built in thermostat set at about fifty degrees F. I only want to prevent freezing at night after I set the plants in the cold frame. I've used the same type heater in my well house to keep pipes from freezing by setting it at fifty degrees. I hate to wake up in the morning with my water pipes frozen solid at the well.

Ted

[AKmark]

Alaskans have tried about everything that is reasonable to change environments. In a large cold frame people have tried water walls painted black, insulfoam with 1" of concrete on a side with foam facing down, retains heat longer, buckets of hot water stationed in it at dusk, I just put a woodstove mine and have went to much greater lengths since to increase production.
Low tunnels will give you about 8-10 degrees if you lay IRT, and 36" hoops with plastic over them, tension wire works great. My friend lays about 9 miles of this stuff every year at Glacier Valley Farm.

[tlintx]

Thanks everybody for the details/experience. I've also been considering how best to get those seedlings started and transplants going early. We have such "almost there" weather here it seems a shame not to try as early as possible!