If you’re growing night-blooming moonflowers (Ipomoea alba), you have to wait patiently for their flowers to appear. Firstly, they like a long growing season and plenty of heat. I started mine early, indoors in pots, and our summer certainly provided enough heat. Secondly, and most interesting, moonflowers are short-day plants. Simply put, they wait for late summer’s short days and long nights before producing flower buds.
It seems a contradiction that a heat-loving plant native to South America waits for short days and long dark nights to produce flowers, but that’s a basic premise of photoperiodism. There are long-day plants, like clover and Carpathian bellflower (Campanula carpatica), wanting long days and short nights. But moonflowers, and also chrysanthemums, are short-day plants and require extended dark hours.
Moonflowers have a photo-receptive protein in their biology that measures the periods of uninterrupted darkness, triggering bud growth when enough consecutive dark hours are available in a 24-hour period. Shine a spotlight directly on them in the darkness and you won’t get flower buds. (Fortunately, lunar and starlight aren’t sufficient to interrupt the budding process.) My moon vines are six feet (1.8 m) from an outdoor security spotlight that’s on all night, but the light is aimed away from them.
Not all plants are sensitive to photoperiodism. Roses are day-neutral plants, not caring how long or short the nights are. Day-neutral plants flower in response to developmental stages in their growth, like sufficient new cane growth to initiate rose buds. Or in response to environmental changes like vernalization, a period of moderately low (but not frosty) temperatures that can induce flowering in plants like orchids and Christmas cactus.
But, back to the moonflowers. I saw the flower buds forming 10 days ago, and prepared to celebrate. It’s an occasion to watch their big flappy petals swirl open, and the event becomes an entertaining ritual. One evening, I sniffed sweet perfume drifting through a window and went out to investigate. There was the first flower, bold as brass and very white, already attracting a circus of moths. The large, dark buds are a bit prehistoric-looking, with a sort of spiky construction around them. The flowers stay open all night, and begin to fold as sun brightens the morning.
Currently, my moonflowers open at about 5:45 p.m., but that will change as the days become shorter and the darkness they relish comes earlier. My plants are shaded at that time; if they were in sun, they would probably open later.
Moonflowers and morning glories are close cousins, and I grow them together in a container on my deck. The moonflowers are larger plants, and they seem to require quite a bit of water. I give them a big drink each night to keep their wide leaves from wilting. Flowering continues for about six weeks, and by then autumn is firmly established.
What a lovely seasonal transition these vines make. An Internet search will turn up videos of moonflowers swirling open their petals, if you’d like a preview.
Hi,I bought a moonflower vine late in June. I transplanted it into a larger pot and have watched it climb all summer. I just noticed tiny buds but are they coming too late to reach maturity? I live in western ny.
Is it normal for the blooms to remain open for a few hours of the day and then fall off instead of closing and opening back up that night?
Your information about moon flowers cleared up concern and shared the mystery of this flower. Patience is not my virtue, but I know now that I must wait, and I shall be rewarded! Thank you.
I have been growing moonflowers for several years and have experimented extensively with them.
I find the best way to get mine to flower earlier and with more blooms is to use a bloom booster fertilizer once a week. Many people will tell you not to fertilize them, but I have found it works very well. I live in coastal Maine so summer aren’t always hot and I find growing them in large pots works well, fertilize with a 10-30-20 once a week, and water daily once they have started to climb.
Love the fragrance of moon flowers.
Hi Judith,
Can you tell me where I can purchase Moonflowers in Toronto? I’ve never seen these before and I would love to have one to start for next year. I live in an apartment with a very large balcony and would love to start a small balcony garden. I’m a night person anyway, so these would be wonderful to enjoy at night.
These flowers are so beautiful. Thank you for sharing the lovely picture! 🙂
Moon
Hello Moon,
Moonflower vines (Ipomoea alba) are really special, and not so often seen in northern gardens. But most summers they grow well, and blossom in August. Mine were really good this year (I think they liked the extended heat). I purchased the seed from stokeseeds.com.
— Judith
Thank you very much! I will check out the site.
Happy growing! 🙂
I love moonflowers and always forget to start them early. This year I found an 8″ container of moonflowers in a local garden center in NH in mid-June and it was loaded with flower buds at that time. I brought it home, repotted it and it has bloomed every single night ever since. I added Osmocote when I planted it in a larger container, plus I now fertilize it at least weekly, and water it daily. It has had at least 2 open flowers every night since I bought it – sometimes more. So I was really surprised reading your article and finding out that it is a short-day plant. Not sure why mine is performing so well, but I hope I have the same results next year. Hurrah for moonflowers and thank you for such an interesting article.
Lynne
Hi Lynne,
What good fortune to find that moonflower plant already started! I can’t give a definitive reason for its consistent bloom all summer, but we won’t complain about the result — lots of flowers. It might have been started extra early; and we don’t know what conditions the nursery gave it to trigger the premature flowering. From the plant’s point of view, the most important thing it does is flower, make seeds and thereby perpetuate the species. Once a plant begins flowering, it wants to continue.
I wrote a blog last year about Christmas cactus, another plant that requires darkness to set flower buds. Several readers wrote in to say their plants never got the dark closet treatment — providing the plant with daily periods of complete darkness — yet still bloomed profusely. Sometimes plants are so aggressively eager to flower, they’ll override the biological blooming requirements.
Tonight I have two big moonflowers open. What a treat!
— Judith
I have a ton of morning glories but have never heard of moonflowers–now I want to try them. It sounds wonderful for evening entertaining in the garden. I always learn something new from Garden Making!
Hi Shana,
If you have success with morning glories, then you should also start some moonflower seeds next year. They grow well together, and both can be started indoors for a head start. You’ll love the gorgeous scent!
— Judith
Enjoyed the great picture of the moonflower as it may be the only one I see. Not a bloom in sight and our days are cooling off. Obviously next year I will have to start them indoors if I want to enjoy their beauty.
Hello Sensible,
Glad you like the picture, it was snapped as the bloom was opening in its swirl of unfolding petals. That’s a difficult moment to catch with a camera!
Yes, an early start, combined with a hot growing season, seem to be the secrets to success with moonflowers. And I’ve had it both ways — some years no flower buds at all, and then a year when they’re opening every night. Keep trying!
Judith