General Question

silverfly's avatar

How do plants know what season it is?

Asked by silverfly (4040points) March 11th, 2010

I have a few random plants in my house and I water them all regularly and keep them warm during winter. I may see some small growth, but as soon as spring hits, they start growing like weeds! Nothing has changed in my house, so how do plants know when it’s time to grow?

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20 Answers

DrBill's avatar

Temp, sunlight (amount), difference between day and night temp, humidity, etc

silverfly's avatar

@DrBill But they’re indoors.

Snarp's avatar

Everything @DrBill said, but I think day length is the main thing. You can alter the blooming behavior of some plants (Christmas cactus is a prime example) by keeping them in a dark room.

This can apply to indoor plants because of the different wavelengths in artificial light versus natural sunlight. But that’s just my assumption, actual scientific evidence could prove me wrong.

grumpyfish's avatar

If I remember my biology correctly, the length of day is the primary trigger for the yearly plant cycles…

CyanoticWasp's avatar

They communicate via the InterRoot.

jeffgoldblumsprivatefacilities's avatar

Plants can sense amount of light versus dark periods. Winter is the season with the greatest amount of dark hours, and as the season begins to change to spring, the number of light hours increases. Plants can sense this shift, and (depending on their phenology), act appropriately; most begin to come out of a state of dormancy. There are other environmental cues as well, but the dark to light hour ratio (aka photoperiod) is the biggest factor. And yes, it even affects indoor houseplants as long as they have some access to sunlight.

njnyjobs's avatar

They observe when you’re watching the weather report in TV. . .

In all seriousness, the intensity of the sun and the length of sunlight for indoor plants can affect their growth, just as it affects outdoor plantings, as referenced in the Farmer’s Almanac.

wilma's avatar

I am very much like a plant is this respect.
The days of longer sunlight, bring me out of dormancy.

CyanoticWasp's avatar

Obviously if @jeffgoldblumsprivatefacilities is correct (and I’d bet money that he is), then gravity must also play a part. After all, winter is heavier than the other seasons.

If the other seasons all have “more light”, then winter must have “more heavy”.

malevolentbutticklish's avatar

@silverfly: It is length of day. If you doubt this grow one under artificial light in your closet.

BoBo1946's avatar

the “wonders of nature!” there has to be a God to make all this work!

davidbetterman's avatar

They are smarter than we think.

MissAnthrope's avatar

In nature, the two triggers for plant growth in Spring are temperature and day length. Most plants will not grow at temperatures below 42 degrees F, and they also rely on a certain amount of hours of daylight per day.

dpworkin's avatar


Exhausted's avatar

I’m not sure about where you are, but I am in the south and winters here are cloudy and the days are short. When it warms up, there is a lot more sunshine and as the days grow longer the plants get more sun, even indoors. I have many houseplants 15+ yrs old. I moved to Colorado for a couple of years and they were more beautiful than they had ever been because it was sunny most of the time and I never had to put them outside they grew beautifully all year long indoors.

unique's avatar

they’re photosensitive…more daylight hours=more grow time.

YARNLADY's avatar

They probably hear you talking about the weather and the days of the year. When you say it’s spring today, they perk up and go for it.

Faze44's avatar


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