Timing of shade cloth usage

[basicallyeileen]

Hello. I've been growing in a greenhouse for less than a year. I've made my fair share of mistakes in this new growing environment, and my orchids are paying the price. I live in the Northeast (Massachusetts). I didn't install my shade cloth early enough in the spring (yes, burned orchids), and now I don't know when I'm supposed to take it down in the fall.

Can someone offer some insight, and I'll write down the dates for when the shade cloth should be installed and removed so I don't make the same mistakes twice?
Eileen

[RosieC]

Of course this varies with where in the world you are and your light levels, but I'm wondering the same thing. I took mine down for a few days recently as we had had nothing but cloud and rain, but then it's been sunny again a couple of days so I put it back early on the first sunning morning. It's a good job I get up early enough for that to work.

[Connie Star]

I'm wondering the same thing. I have what I call a "shade table" as it's too small- about 3' wide x 8' long and I have a 75% shade cloth- also in Massachusetts. When the sun went lower in the sky and a few leaves were unshaded in July, they burned. So, when at this latitude should the shade cloth come off? Eileen, if you're in a green house, don't you get some filtering from the glass, or no?

[basicallyeileen]

I'm glad I'm not alone in this question. I didn't think to add this information: my greenhouse is 5 wall polycarbonate and the shading is 70% aluminet (it's reflective along with shading). Connie, I believe there is light transmission loss through the polycarbonate, but I don't remember how much. The greenhouse faces southeast. By ~2pm it's in the shade.

[Connie Star]

I think the "glass" cuts quite a bit- is the 70% aluminet built in to the walls? If so, does the 70% include the glass and the aluminet?
I'm also wondering when to bring my orchids in from the cooling nights. It's been such a crazy summer, weather wise.

[RosieC]

I think you get some loss of light even through plain glass and I think pollycarbonate greenhouses give a higher drop in light. Mine is a double layer polycarbonate and diffuses the light a noticable amount... although it still needs a shade cloth in the summer for orchids.

The other consideration is angle of the sun changing. My greenhouse now gets less direct sun than mid-summer, due to the angle the sun is coming from and where the other building are. I'm seriously thinking I can take my shade cloth down now, but if it was in a different position in the garden that decision might be different.

Hmm... makes it very difficult to say/advise.

[kamlesh711]

What I did, is have 2 layers of 50% shade clothes (effectively 75%) for peak summer from April - Sept

and remove one layer for the rest of the months

I might be cutting out too much light than would like to, but the high temp. stay in reasonable limit

[richardb]

Like most UK people, I took mine off thinking that the good weather was over, then the sun came out again.
I have not worried, because I think that some low Autumn sunshine does no harm to the plants for just a few days. Anyway, my greenhouses are lined with bubblewrap ready for winter and that diffuses the light quite a lot, and I have not yet washed the outside of the glass either so that messy surface will take some light too.

[Royal]

One thought to add: while the angle of the sun changes, so does it's distance from earth (or I should say the earth's distance from the sun changes). Sunlight can be a more intense when it's at a closer distance - just ask a snow skier.