Good question. This is what I do to make life easier for myself and less risky for the plants. I take my plants out in two waves. In the first wave, I haul out the hardier subtropicals that I've been overwintering in a detached minimally heated garage/semi-converted greenhouse. This plants have been kept frost free but relatively cool over winter (between about 60 F and 40F). I wait for minimum temps to stay above 38 F.. I can usually do this in the first half of April. This group includes all my citrus (lemons, oranges, kumquats, etc.), Washingtonia fans, date palms, and hardier cycads. In the second wave, I move out the true tropicals (bananas, aroids, and tender palms (such as the Manila palms). Generally day temps are in the upper 60's-70's (nights 50's). I can often do this by late April. This spring, I haven't had any problem with the first wave (despite some near record cold temps recently), and am waiting for the weather to cooperate more before starting to haul out the more tropical species. Of the plants that you mentioned, I've already put out the epiphyllum. If the cannas have been in active growth, I'd hold off, the only bananas I have out is the Chinese and Japanese varieties, I know nothing of brugs, fushias should be fine outside, as for the annual--it really depends (some are quite tropical),plumbago should be okay, jasmines (depends on the variety). Although I put my tropical hibiscus out, they are sort of intermediate in cold/cool tolerance (mine seem okay though and they've been out for about two and a half weeks (did sun burn though). Hope this was helpful and good luck!

just wanted to add my experiences:

citrus, bananas, cannas, brugs, alocasia, colocasia, plumeria, hibiscus...if they have been given a head start indoors and are already growing, then upper 30's at night is reasonably safe. But consecutive cool and rainy days are not.

It's not strictly the cold temps - it's also the daytime warmth and the level of moisture that need to be judged while making the decision. It's kind of like an art, you need to get a feel for it.

I've had all my tropicals out for a few weeks already, the temps dipped to 39 with frost last week one night. My alocasias had some fried leaves but that's it. The hibiscus are still holding onto their flower buds.

Of course also keep in mind that during cool spells, these plants are not going to be growing, so if you don't have patience then you can keep some specimens growing indoors and plant them out later.

Thank you!! It's so complicated to keep track of each plant's individual needs. I think I'm probably being conservative--but with my short growing season I try to be cautious. Right now I'm only leaving brugs, fuchsias, and some cold-tolerant annuals (and the geraniums) outside at night.

Do y'all think that one cold night will stall the plant's growth for a significant period of time? I swear the plants I've been lugging in and out really look good--it's a lot of effort, but they look much healthier. So several cool days are worse for keeping the plant growing at a good rate than one cool night? I'm trying to maximize growth...

The highs here this week are anywhere from 60 to 67 (today is a unusual 77!), and the lows are 40-48 (with 58 tonight).

thanks so much for the help!

Elizabeth

cool + wet = higher chance of rot

Cool weather seems to stall growth only until it gets warm again.

The reason your plants are looking good is because when you bring them in at night, you're keeping the soil temps warm. Warm soil keeps roots active.

I think average soil temps of about 60-65F are enough for growth of tropical plants, but some like it much higher. If you average the day and night air temp you'll get an approximate soil temp. Timely watering with warm water can help significantly.

Zone 5a here Elizabeth,

I wait until June 1.
It's hard.... I put an extra ( sacrificial) pot of 6 ft tall papyrus out just to see how it handles the wind if the fronds are tied together.

The wind storms are real tropical trashers...
and they never let up until May is OVER.
We are still having spotty hail storms too.

It's hard I know to wait..
We're all in this together-
Karen

I've been tempting fate myself because it is not warming up as fast as usual here, and I just don't have room inside. Brugs, mandevilla and plumeria have been out with temps down as low as 40 and seem ok. Orange and lemon of course are fine and covered with buds. Musa basjoo in the ground is about 3 ft tall now and seems unfazed.

You could also group them all together and cover with a row cover or an old blanket at night.

Occasionally, on various websites or news articles on putting tropicals outdoors for the summer, they will warn you not to put your tropicals outside unless the nighttime temperatures are staying above 55F or warmer. If I followed this it would mean my plants might only be outside from mid June to early August, if that.

I started putting my tropicals outside on days when it reached about 55 - 60. I figure the sunlight keeps the plants and soil warm, especially if little wind. They came in at night though.

Now things are starting to warm up a bit more they are staying out at night. But, knowing the spring we've had (cool and windy) I'll likely be covering them with a blanket if frost threatens. It gets tiring carrying plants indoors every night, but by the time it's time to plant the garden they are definitely hardened off.

Glen

Yesterday we had a high temp of 81*! I had all the plants outside, basking in the warmth and humidity. Then I had to haul tons of plants back inside because the low last night was 40! Today high of 55 or so, with a low of 39.

I have many annual seedlings that I grow under lights. I read recently that vinca doesn't like night temps below 60* (or so, depending on which source you believe)!