Growers, how do you harden off in a greenhouse?

ellen_inmo(6)April 23, 2005

I worked in a greenhouse for a short time, but not long enough to learn everything. Since then, I have been growing on my own, in my home, with grow lights. And every year, I spend two to three weeks aclimating my plants to the outside conditions before I will dare put them in the ground.

I've been hardening off for at least two weeks now. And every single day, I go past the nursery in town, and they dont have a single plant outside. All their plants are inside the greenhouses, for sale. I just have to wonder, are those plants folks are buying hardened off, and if they are, how do you do it without ever leaving the greenhouse???? Is there a way to do this? I guess I am envisioning dropping the day and night temps in the greenhouses. But what about aclimating to the sunlight? I find this to be the most important part of hardening off, and I am quite meticulous about it. Already this year, the tops of my Millets were sunburned, and I thought I was being careful.

I cant recall ever buying plants that were bought in a greenhouse,and them dieing right away.

Will you share with me how this is done?

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calliope(6)

I move some material to the perennial house. The temps in there are ambient, but it has a little solar gain and I can kick on the heater to keep it just above freezing if I wish. It also has a roll-up vent and I love the circulation that gives to these plants.

Annuals I move in there are those I don't want stretching or moving too fast. Petunias, cole crops, pansy, things like dusty miller or calendula.

I think you will find MOST greenhouses do not harden off right before the beginning of sales rush. In fact, some hold their plants back, and then push them before Mother's day. The thing is maximum turn over on bench space anymore.

No, I do not harden my plants off to sunlight. The light levels in a properly situated growing house go off the meter. I have already thrown shade on three of my four growing houses. Always have shade on by May first.

    Bookmark   April 24, 2005 at 9:41AM
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Hap_E(z9 Berkeley CA)

Greenhouse plants are not hardened off, even without shade cloth they are not getting enough UV to be ready for full sun.

Most of my selling area is out in the open, so I have to harden off my greenhouse grown plants before they get moved in to stock. I mostly grow ands sell cacti and succulents, with a few weird native and xeriscape rarities thrown in, so I am running a specialty line that may not be comparable to the average nursery. But any plant that is meant for outdoor use I try and have pre-hardened before it is sold.

However there are times that I do bring plants straight out of the greenhouse and put in stock under a shade awning, when I do, any customer who buys one of those plants is given an info-card on how to harden off plants successfully. Small "shade cloth and bamboo pole kits" are available for those that want to get their plants in the ground right away, without waiting to harden off. Any shade-kits returned in good condition receive a store credit.

By making sure that we talk to every customer and be proactive with them, I help them realize why they should keep buying from a small local grower-retailer, rather than picking up half dead "bargains" at one of the local big box stores. When they ask why my plants look so good compared to the" bargains" it is usually easy to make them understand what local grown, in soil designed for our climate (not Southern California where the big box stores import from) means.

    Bookmark   April 24, 2005 at 11:27AM
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calliope(6)

You have to consider what you are growing, as per how high a light level you want to maintain in the growing houses. I can reach 10K footcandles on a bright day and that is just too much light for many things. I prefer to run smaller and more g'houses than try to accomodate my whole line in one area. This gives me flexibility as to the environment for crops of similar cultural needs. I also grow winter crops in a relatively northern latitude. Then getting enough sunlight is important. Even dirty film or shadows from the purlins can cast too much shade to keep a crop from internodal stretching.

    Bookmark   April 24, 2005 at 3:50PM
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