Asked February 9, 2018, 6:52 PM EST

How can I get an old greenhouse to produce again?

Over the years, a mossy-like, brownish film has engulfed the outside acrylic/fiberglass siding. It gets really hot and we have a shade cloth on the roof and we have two box fans that blow air in and a large greenhouse fan to suck the hot air out. It gets full sun most of the day.

I think that it's not getting enough light in, but I am at a loss. None of my tomatoes produced once I took the lights off the young plants. Any suggestions? Nina Hurst

Deschutes County Oregon greenhouse horticulture

3 Responses

Hi Nina,

Is it possible to replace the glazing material(fiberglass) with new material such as double wall polycarb or greenhouse grade plastic (polyethylene)? If you cannot replace the glazing material then you will likely need to have supplemental lighting depending on the crop. Also there are ways to provide passive cooling. Without knowing what type of ventilation (not the fans but the openings in the glazing) you currently have, I am not sure what else to suggest. Feel free to give me call for additional information.

The openings or windows are where I have box fans to push air into the greenhouse. They are located at the west side and the south end of the greenhouse. There is a window in the door at the opposite end of the greenhouse that has a screen I leave open. At that end of the greenhouse I have a large commercial grade greenhouse exhaust fan to suck the extra heat out. There are two small vents at ceiling level that can be opened, but I'm not sure how much that would help. I have sensors that I have in the greenhouse that measures current temperatures that are registered in the house. Fans are on timers and go on and off at preset times for the hottest part of the day. It also is quit short from floor to ceiling which makes it so hard to get rid of the trapped heat.

The greenhouse is 8'x24' and it would be quite expensive to replace. The only thing I grow in there is tomato plants in 2'x6' metal stock tanks. The planting beds totally rotted over the last 30+ years and the stock tanks were the best solution for replacement. I have added permanent lights (LED) above the 3 planters. I don't know if there is anything else I could do. Is there a secret formula in fertilizers I could use that would insure a good crop? I will be at the LOAFA conference on the 10th of March to check out soil options I may have.

I have posted a few pictures that may help. The first one shows the door at the end with the window screened. The second one shows the planters I have to use. The third one shows how opaic the siding of the greenhouse is. Let me know if I need more pictures.

Thanks, Nina

Hi Nina,

The best way to release heat is through roof ventilation, so I would encourage you to use that or increase the amount of ventilation in the roof if possible. It would be helpful to see the ventilation in its entirety. So pictures of the vents from a distance. Passive ventilation can help if on opposite ends of the greenhouse, with one down low (windward side) and the other up high (leeward side). If it gets too hot in the greenhouse this will negatively affect plant growth and pollination. There is not a fertilizer that will produce a good. The growing conditions need to be ideal, meaning not to hot and pollination needs to occur -sometimes by hand in a greenhouse. Ideal temperature range during daylight hours for growing tomatoes is between 70 -80 degrees F. Thanks,