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Hardening off

Posted by novelist 5A (My Page) on
Tue, May 4, 10 at 9:59

I have a number of things started from seed, grown in my basement under a combination of MH and HPS lights. They were all doing supurb, so last weekend I moved them to an unheated Greenhouse that is built with polycarbinate siding an roofing. It's double panel poly. The plants receive sunlight filtered through that poly. My plan was to let them acclimate in the GH for two weeks, then transplant them.

In the GH, thye are getting sunlight, but it's filtered by the polycarb. The location does not get full noonday sun, just moring and late afternoon.

Will these plants need to be hardened off to the "real" sun, or is the GH experience enough? Last year I skipped the GH step and moved directly to hardening off in the shade and for limited time. It worked pretty good, but I am now using the GH as a secondary step for plants before real outdoors.

This worked well for onions, shallots and leeks. They all were born under the lights, moved to the GH, then put out in the sun. They did not get any hardening time between GH and full sun, but it was late March, early April and the sun angle and intensity were less than now.

So, tomatoes, peppers, vines? GH or let em out to play?

Follow-Up Postings:

RE: Hardening off

My plants go straight from my polycarbonate covered greenhouse into the ground without problem, but I get noonday sunlight. I would bet that there is enough UVA, violet and blue light in MH light to condition them for outdoor sunlight.

RE: Hardening off

I'd harden them off. As long as you gradually acclimate them to sunlight, the greenhouse is probably an unnecessary step. But don't move them straight from lights to full sun.

Another option is to plant them out but make a little open-sided "tent" over the seedlings using a bedsheet or row cover, to filter the sunlight for a week or two. That worked well for me and was less work than moving the plants around.

RE: Hardening off

One vote for and one against. So, I guess it's ok that I'm questioning this myself.

My greenhouse is not used so much as a hardening off phase; it's more about space issues. My grow room, with 4 HID is about 75 sq ft of space and my greenhouse has about the same. So when it's warm enough for a particular crop to go out, I move it and start the next round of little ones.

I'm in Zone 5 (close to zone 6), so last weekend I moved Tomatoes and Artichokes out. Next weekend, it will be peppers.

I think I may try an experiment and harden off a few and plant a few and see what the difference is.

RE: Hardening off

I would think the hardening off process could be sped up after the GH. Try one plant. Start with 4 hours sun the first day, 8 the second, morning and late afternoon. I think that's all they'll need. Personally I'd stick one out in full sun just to see. I don't have a GH but I harden my plants off in 4 days starting with 3 hours in the morning and move them further away from the house each day until they get sun from 9am to 4pm then they are ready. I start under overdriven fluorescents which aren't as good for preparing them for sun as your MH.

RE: Hardening off

I just went through this, and will have to agree with Taz. Several different plants, all more than survived, they are now thriving in the sun.

RE: Hardening off

The one aspect the GH may not address is the wind. Plants not conditioned to it would have been snapped in two by the winds we had yesterday and it wasn't even storming! I have an oscillating fan in mine that runs 24/7 and none of mine suffered any damage.


RE: Hardening off

I didn't harden off pepper seedlings that I started under an HPS fixture and they did fine being transplanted immediately. I also put brassica seedlings started under a fluorescent fixture under the HPS bulb for a couple days prior to transplanting and they did ok.

RE: Hardening off

When I move my tomato and pepper plants from inside under fluorescent lights to my greenhouse, I cover them with a laundry basket for two days, unless very cloudy, then remove the basket.

When the greenhouse gets full, the oldest are moved to an outdoor shelter I built from old storm doors and a sliding patio door screen. This protects them from hail and strong wind. There, I partially shade them for two more days with a section of wooden slat fencing that reduces their sun exposure by about 50%.

Then, they go to the garden.

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