Healthcare of Plants in the Greenhouse

Is there any forum specifically about plants in the greenhouse? I have some plants I am trying to overwinter and, while some are doing okay, other are starting to get yellow leaves, or losing leaves, or getting spots. I need some help on how to keep them healthy and alive. Any advice on where to turn for this information? How low can you keep the temp in the greenhouse while keeping the plants healthy? Do you spray they with a fungicide or pesticide? I'll appreciate any and all advice! :)

Allie, this is the place.

Do you spray they with a fungicide or pesticide? Pesticide, yes. Fungicide, only on the Plumerias that stay in the GH.

How low can you keep the temp in the greenhouse while keeping the plants healthy? Depends on whether you want survival or growth. My experience is that I start to have more trouble under about 55F.

We can offer much more help if we know which plants you have.

SB

Allie what kind of plants are you growing?

MollyD

Okay - I have some cuttings of impatiens, ivy and coleus growing in there. I also have two mandevilles, two hibiscus, and some lantana. I have a few "houseplants" that I am not sure of their names and I am trying to overwinter a pentas, as well. I guess that is it mostly. I have a jade plant and a jasmine plant in my house for now. I mostly want to keep the hibiscus and the mandevilles alive. I also want to grow seedlings in there, as well. Thanks for your help, SB and Molly!

Allie those are mostly very tender plants. I think I would aim for a minimum of 60 degrees and 65 might be better. Your 'toughest' plant in there is probably the ivy depending on what variety. Some are extremely hardy and can take freezing temperatures while others need milder climates. Same for the hibiscus. There are tropical and hardy hibiscus. I've never grown mandevilles but I believe they're tropicals.

MollyD

You can get by with lower than 60 degrees if you don't care if they grow much right now. all the plants that you mentioned can get by with 45-50 degrees at night if all you want to do is hold them. If you want active growth, then you should set the thermostat at 60 for nighttime. The one that will be affected the most would probably be the impatiens-that I have never tried to keep at 45-50, the rest I have-even cuttings root then, because they get warmth during the day from the sun. I don't think the impatiens will die or anything at 45-just not do anything. Experiment-try the 45 or so for a few nights and see how they look. If they start to wig out-turn the temps up to 50, etc

Thanks so much for your help. I am not aiming for growth - just to stay alive. They all look okay, although I have a few that look stressed. Maybe I'm not watering enough - or too much? What do you think?

If it's the hibiscus that have yellowing leaves or some leaf drop it may be nothing to worry about--they tend to do that as a response to stress caused by change in temperatures, moving from outdoors into the greenhouse, etc. If it's the other plants, I'd suspect overwatering.

Are you finding that the plants that have yellow leaves are dry when you go in there, or do you water regardless of whether or not the soil is wet? If that is the case-then do the opposite! Water the dry plants a bit more, or allow the wet ones to dry out some. Like ecrane said-the hibiscus do have a habit of dropping/yellowing of their leaves when they are stressed-like too dry. Some will just drop their leaves in colder temps and then in the spring when its warmer, they will put out new growth.

Whenever I leave town, I have to leave detailed instructions with someone for the greenhouse. Spring summer, I tell them, "When in doubt, water." Fall and winter, I tell them "When in doubt, don't water."

HTH