All numbers are approximations.

Purchased an 18" pittosporum about 18 years ago at Target and transplanted into it current large pot a few years ago. Maybe five years ago it began to drop leaves, mainly in the warmer months. 1.5 years or ago I rooted some angel wing begonias and placed them in the pot. Last summer, it was dropping a lot of leaves and had much scale. I would wipe them off plus add a systemic and they would reappear. I then read that over-watering would attract scale. I stopped watering in July. It grew new leaves over the winter and still no scale despite reoccurring infestations on my agave, hibiscus and arrowhead plants. How is it possible that the plants continue to live, especially in non-humid Colorado?
Photo from my west bedroom.

Hi & welcome! I think you answered your own question for these particular, beautiful plants. The appearance indicates they've been in low-light mode for a while, so the metabolism would naturally slow in response to that.

Any plant will keep living until it gets too hot, dry, cold, roots so soggy that they rot, or other occurrence that is fatal. I didn't water the plants in my shed at all for 4 months of winter. All are fine.

I had a Dieffenbachia that I didn't water for 2 years. The leaves fell off but the stems stayed firm and green. I cut those off at the soil level, stuck some in water and some in soil, and all are great looking plants again now. It just depends on the specific set of circumstances and individual plant.

Love your dressers too!

It depends on a plant and growing conditions. In case of tropicals (most houseplants) they go semi-dormant at about 65F with lower light up north.
Some cannot be dry or they will die. Others can regrow from stem/tubers.
Specifically I left my sansevierias and jades for 2 months at 66F in NJ as is , no water and they shriveled up, but rehydrated once I started watering again.

I have some crassulas cuttings I think are about 18 months old. Still viable, not sure if they count.

Thanks for sharing stories about your "camel" plants!

My thermostat is set at 64 during the day and shut down at night. When I go on vacation, I set it to 50 (for the water pipes) with no visible ill-effects on the plants. I know a young couple that leave lights on above the plants and the thermostat set at 72 regardless of whether they are home. I told them my real world experience to no effect.

I am anxious to continue this experiment but I feel that by the time they begin to show effects, it may be too late (1-2 of the smaller begonias have died).

Many of my plants spend the winter in unheated rooms. The temp stays above freezing in those rooms, but some mornings I can see my breath. Various plants react to this in various ways. The only generalization I can make is that most of them stay alive. That doesn't tell you anything because you don't know what plants they are, and I can't tell you the exact temps.

These kinds of observations are interesting, but because there are so many variables, and sooooooo many plants being cultivated as houseplants/permanent potted plants, they aren't useful for making generalizations about plants in general, or even the same kind of plant. For example, a tiny specimen in a giant pot next to another specimen of the same type of plant that is much bigger and in a smaller pot can't be compared to each other even under identical care and conditions because it's not an apples-to-apples comparison if the plant-to-soil ratio is so uneven.

Nothing wrong with any experiment, IMVHO, I do a lot of them. Just don't be too bummed-out if you kill your only copy of something, if you are experimenting that way.

Begonias don't stay alive for long if the soil dries out.

50F is quite low for semi-tropicals, but mirrors dry winter period , though outside temps go up to 60-65f during the sunny days and the humidity is higher then indoors. A lot of plants drop their leaves.
So in your case if you position yr plants near sunnier warmer windows when you go away, they will probably warm up to 60F, unless you live in colder cloudier climate, where temps near windows will drop at night 5-10f and won't warm up during the daytime.
for true tropicals temps below 60-65F for extended periods will mean death or severe decline. Basically it weakens the plants, so if they are small and not robust they will not survive. Weaker plants invite diseases and pests too.

The scale infestations could have resulted from those 10-14 days at 50 degrees over christmas.

The insects usually wake up with warmer temps and go dormant below 50-55F. So the eggs were there to start with or from new plants.
The info on the pic you posted is generic, it is far better to seek recommendations for each plant you grow.

I decided to water this week. The water just ran right through the pot. To saturate the soil, I had to add slowly over a few days.

I hope it goes well, best luck!

After about a week, leaves began to fall (and continue).