How much earlier can I plant with a cold frame.

I planning on building me some raised beds and start gardening with this style and I also want to build a cold frame so I can get an earlier start. So what I'm thinking of doing is to build my raised beds with some type of lumber, approximately 3 ft. wide by 15 ft long, fill with soil, and then also build a hoop house over these beds using pvc and plastic. Each bed would be for tomatos, cucumbers, squash, maybe watermelons and cantalopes. These veggies mentioned I have a hard time with once the summer heat drought starts. In my creek bottom the last frost isn't until about the last few days of April or the first few days of May. I set my plants out as soon as I think it is safe enough from the frost. They grow real good and have lots of fruit on them. But it seems I only get one good picking off of them and then the summer heat drought hits (usually soon after the 1st of July) and starts scourching everything. My tomatos will scald on top, squash will harden on top, cukes scald on top, and my watermelons and cantalopes become stunted. So my question is how much earlier could I transplant if I had a cold frame over my raised beds? Also I figured if I leave the hoop frame in place after its warm enough to remove the plastic then I could use some type of a shade cloth to keep my plants producing longer when the sweltering 100 plus temperature arrive.

 

The greatest thing about gardening is trying new things. Cold frames will extend your season for many crops, but I don't think you'll get any improvement with the crops you've listed. The cold frame helps plants get through cold temperatures by slowing the temperature drop. The temperature gradually becomes equal to the outside temperature. They wont let you grow warm weather crops. They work great for things like spinach, escarole, and some other cold weather greens. I remember reading in Organic Gardening magazine that for tomatoes, 2 weeks head start at the beginning of the season translates into a few days at the end.

A few pointers on boxes: don't use wood if you have other materials. If you use wood, put a plastic liner between the soil and the wood. Don't use screws or nails to hold them together because they'll fall apart in a few years. Get angle bracket material, drill matching holes, and use nuts and bolts. They'll last decades! Consider drainage. Its a lot easier to run a plastic drain pipe under the boxes before they are filled with dirt. (I learned the hard way)

A few pointers on cold frames: you have to be able to easily open and close them. If you use plastic tube, they won't last very long. The sunlight breaks down the plastic and in a few years they are so brittle they break easily. I made one last year using 3/8" rebar, a piece of cattle fence, and plastic sheeting. Total cost was less than $20. You can plant seeds while the ground is workable in late fall. This gives the best jump on the spring. You'll have greens in late Feb.

 

I've thought of doing much the same thing, RH. I think you'd get a few degrees warmer from the heat radiating from the soil itself. My 6' tall hoophouse worked that way this year. I didn't put a heater in there at the beginning of cold weather and it got down to the upper twenties one night. Everything up high on tables and in hanging baskets got bit pretty good, but NOTHING on the floor did, not even the low growing tropicals. I'll bet you could help your cold frames along a lot by covering the whole thing with blankets on those really cold nights.

I also thought I'd offer a few tips on growing things in a hot climate in the heat of summer. You may already know some of this and if so, I apologize ~ just throw out what you don't want and use the rest if you like.

My garden always used to crisp up like you describe until I quit listening to my neighbors about "drowning" my plants if I watered more than two or three times a week. I water EVERY DAY in the real hot times, leaving the water on for atleast an hour to soak the beds to the very bottom and a couple more feet down for good measure. I used to use an overhead sprinkler ~ yes, the squash got powdery mildew, but they would have died completely and taken everything else with them had I not. Now, I use soaker hoses in some of the beds and it's remarkable the difference! But soaker hoses are expensive, so I've thought of poking holes in a bunch of old garden hoses I have. Might work.

Also mulch, mulch, mulch! Last year I tried alfalfa hay about four inches thick. Talk about a difference! It holds in a lot of the moisture AND keeps the ground cooler so it doesn't toast the plants' roots. And it helps a lot if you put the soaker hoses UNDER the mulch.

Lastly, the shade cloth is a good idea. I tried shading some plants one year ~ planted sugar cane in one bed and then planted the things that are more susceptible to the hot sun in the bed next over to the east of the cane. This way, the plants get shaded from the killer evening sun. Worked rather nice. BUT it was only good for the plants in that one bed directly to the east of the cane. I think your shade cloth idea would be lots better.

 

Zone 4 here, south-central part of NY, way up on top of a hill. I built a few raised beds this fall, and fitted 2 of them with pvc hoops. The plan is to stir up the dirt/manure/etc., and staple plastic on in mid-April, and plant several lettuce varieties, cabbage, bok choi, and scallions. I may put several water-filled milk jugs in to act as heat collecters. This will give me a head start, but not on heat-loving tomatoes and peppers. I'm considering purchasing some floating row covers, and using them for squash and corn. I understand I could get a couple weeks jump this way. Well, so much of what I do is experimental, I figure I have little to lose by trying it. I'd like to get most of the kinks worked out, so I can offer a mini-CSA (to co-workers) in a few years. I'd like to initiate this when the asparagus, fruit trees and blueberries are producing well.

 

My understanding is that the plastic over pvc moves you one zone south in terms of growing. We haven't focused as much on getting stuff in early but have used it to keep our tomatos and various greens (Kale, Spinach, Swiss Chard) available through November for the past couple years. Our beds are closer to 4 foot wide and we use a row of 10 foot 1/2" PVC Pipe attached to the wooden bed frames with 1/2" U straps. Works like a charm. I am thinking of reconfiguring 2 of the beds to make a larger standup greenhouse. We'll probably use 3/4" PVS for that and put a fan in.

Mike

 

"...I may put several water-filled milk jugs in to act as heat collecters. This will give me a head start, but not on heat-loving tomatoes and peppers...."

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So is it my understanding that by using the milk jugs in the spaces, you are in essence warming the space by the heat they radiate? Do you bury them partway or just let them sit on top of the soil?
Thank you for answering this simple question for me. I am trying to learn all I can about using cold frames.
We are in Zone 5 I believe (Billings,Mt)

D

 

Maybe run a extension cord and plug in a infrared heat lamp on those really cold nights. Might could put the heat lamp on a timer so that it comes on about midnight/1 am. and shut off at daylight. I'm starting to like the ideal of this cold frame more and more.

 

Perhaps you could use the manure / compost method to heat, turning cold fram into hot bed. http://www.savvygardener.com/Features/cold_frames-hotbeds.html