I want to move all my indoor houseplants outside in a makeshift plastic greenhouse. Will this be ok?
It depends. Some plants are appropriate for keeping in an unheated greenhouse during the winter, and others are not.
If you are in an area with cold winters, check the winter hardiness zones recommended for each of your houseplants. Also check the temperature inside your plastic greenhouse during the winter, at night and during the day. If the temperature drops below a level that is safe for your plants, they could be killed by the cold if kept in your greenhouse. Plants in pots are also more sensitive to the cold than those in the ground.
https://www.gardeningknowhow.com/garden-how-to/info/the-importance-of-regional-gardening-zones.htm
I'm very interested in bathroom plants and want to know more about which plants can live good in this environment? Is there a long lifetime for specific bathroom plants? And how long will this be? I hope that someone can tell me more about the possibilities with plants in the bathroom. Or know some interesting information to take care of bathroom plants.
These articles will help you with plant selection.
https://www.gardeningknowhow.com/houseplants/hpgen/bathroom-plants.htm
https://www.gardeningknowhow.com/houseplants/hpgen/indoor-plants-that-need-low-light.htm
My husband and I agree that our houseplants should be rotated, but we disagree on the following: He believes the older leaves should face the light, but I think the newer growth should have more light to encourage it to grow more. Any advice?
This article should cover your question.
https://www.gardeningknowhow.com/houseplants/hpgen/rotating-houseplants.htm
Does LED work as well as fluorescent for growing indoor plants?
Yes, there are LED grow lights available.
May I put my ZZ plant out on an east facing patio this summer?
Do not expose the plant to any direct sunlight.
https://www.gardeningknowhow.com/houseplants/zz-plant/caring-for-zz-plant.htm
What type of pots are best for indoor plants? I mean, I've seen people using margarine containers. But wouldn't that put plastic residues in the soil of the plant? And then maybe we would end up eating that residue, with a veg. or herb plant.
This is a good question. Plastics labeled 3, 6, and 7 (in the recycling symbol on the bottom) are thought to be the most likely to leach toxins. Other plastics are likely safer, but you may wish to avoid them all to be sure. Of course, you must consider whether the container was previously used to hold something toxic. When using old containers found in a garage or antique shop, it's best to avoid any painted containers in case the paint contains lead. Also, any salvaged wood that is stained green may contain arsenic preservatives and should not be used to build raised beds or other food gardening containers.
Terra cotta/unglazed ceramic or untreated wood gardening containers are likely safest.
Which direction to rotate plants?
It doesn't matter which direction you rotate them. just move them the opposite direction that they curve to the light.