How do indoor plants know what season it is?
How do your plants know to flower in summer and – if appropriate to the plant type – turn dormant in winter? How do they know when spring is coming? Inside a house, the plant has fewer clues to guide it on the seasons, but it can still tell what time of year it is.
The amount of light available and the temperature in the room are the main season determiners for an indoor plant. Admittedly, inside a house, the temperature levels will change less, but they will still alter between winter and summer, and your plants will detect these changes and respond accordingly.
Are Indoor Plants Affected By Seasons?
Yes, indoor plants are affected by the seasons, or at least, many of them are. It is possible to trick plants into thinking they are in a different season to the actual one by mimicking the conditions they would experience in – for example – summer when it’s actually winter outside.
Your plant does not have a magic way of knowing what time of year it is.
It is affected by the seasons because they dictate how much light it can utilize, how warm it is, and how many insects are likely to be around to fertilize its flowers. Your plant doesn’t know there won’t be too many insects inside!
Therefore, indoor plants aren’t affected by the seasons if you take away the two things that tell them what season it is: light and temperature.
If you give your plant artificial light all year round and keep the temperature consistent from month to month, your plant is not going to be able to judge what time of year it is.
However, this is rare in most cases. Usually, outside light levels and, to a lesser extent exterior temperatures, will affect your plant even in the home.
In summer, bright, hot light will be pouring through the windows. In winter, the glass might frost over, and the plant will get a lot less daylight – as well as daylight that is angled differently.
These things guide your plants’ behavior and tell them how to grow, when to flower and when to seed.
You will even notice that some plants go dormant in the winter, regardless of the temperature in your home – this is triggered by low light levels. Some will shrink back and seem to die off, while others will just grow more slowly.
If you watch your plants, you’ll notice that while being in the home may mitigate the effect the seasons have on your plants, they do not stop it entirely, unless you make constants of the conditions that the seasons change.
How Do Seasons Affect Your Plants?
Plants use the seasons to regulate their behavior.
For example, plants that flower in spring need to know when spring is coming. They are likely to be fertilized by insects that are particularly active during the spring, and therefore it’s important for them to get this right each year.
Of course, the different seasons affect various plants in entirely different ways.
If you have chosen to grow annuals inside, you will notice that they die come winter, and you’re very unlikely to be able to pull them through no matter what you do – because they have reached the end of their lives.
If you have a Venus Flytrap, for example, you might notice that it shrivels right back down into its pot when the year gets colder. That’s because it has gone dormant, and is saving its energy for next spring. There are unlikely to be many insects for it to catch during the winter, so it is waiting for warmer weather to return.
Equally, in summer, you’re likely to see more of your plants blooming and putting out new shoots.
They know this is a good time to grow because there will be more pollinators around.
Having plants indoors can somewhat alter their schedules, however.
You may notice that flowers bloom earlier indoors than out, or grow faster on your windowsill than on your patio.
That’s because they are experiencing artificially warm temperatures, and they are therefore a little ahead of the schedule the outdoor plants are following.
How Do Plants Know When It’s Winter?
Winter is probably one of the easiest seasons for a plant to detect, even indoors.
Temperatures are likely to be lower than in the fall, and while they might be artificially high, they will still have dropped. Your plant may just think it is experiencing a mild winter.
More importantly, however, indoor plants know it’s winter because the light levels will be lower, and the quality of light will have changed compared with the warmer seasons.
The light is hitting the Earth at a different angle, and is therefore much less intense.
Your plants will have less light and will photosynthesize less, slowing down or becoming dormant.
It’s important to know this, and to understand how your plant behaves in the winter:
- Most plants need less water during the cold months (due to reduced activity and reduced evaporation).
- You might also want to shift your plant somewhere that it will get more light, so it doesn’t suffer too much from the increased darkness.
In some circumstances, you may need to provide an artificial light to ensure your plant has enough to continue growing. However, this should be done with a good understanding of the plant’s needs, and should not be kept on at all times.
Installing something like this LED Grow Light Bulb is an option.
How Do Plants Know When It’s Spring?
Your plant uses the same tricks to know when spring has arrived.
Plants know that spring is coming because the daylight will be increasing, and the quality of the light increases. As the hours get longer, the temperatures creep up, and the angle of light alters.
Early spring plants will start to grow quickly, taking advantage of openings left by winter.
If your plant needs fertilization in order to thrive, spring is the right time to fertilize and again, make sure that it is getting enough light.
Protect it from cold snaps and try to keep the temperature constant if possible. While outdoor plants have to deal with fluctuations, indoor plants are likely to be happier and stronger if you keep the temperature steady.
They will have less resistance to changes, and might suffer if it’s hot one minute and cold the next.
Other things you can do in spring to help your indoor plants is change its soil and pot if it has outgrown it. Here is an article to help you decide if it’s time to repot and how to do it correctly.
To summarize, here is a short spring care checklist for your houseplants:
- Move it in a place with lots of light
- Fertilize if plant requires it
- Keep a mild, constant temperature at all times
- Change soil and/or repot
How Do Plants Know When It’s Summer?
With the sun at its fullest and temperatures peaking, plants indoors will be in no doubt that it’s summer.
They will feel the heat through the windows, especially if they are plants that enjoy direct sunlight.
You will probably see them respond with rapid growth, flowers, or even fruits (depending on the kind of plant).
Some may need you to help pollinate them using a paintbrush, as they are unlikely to be pollinated by insects while inside.
You might also have to move plants away from windows or shade them from the direct rays of the sun.
Outside, plants are unlikely to get a full, uninterrupted hit of sunlight for hours on end, so your houseplants may suffer if they suddenly find their leaves under the intense rays.
Try to pull plants back a bit from the windows, or put some paper or thin fabric to shield them.
Few plants will enjoy getting direct sun for hours on end.
Even sun-loving plants may dry out, and their roots may get hot – which will cause them to suffer. In a pot, they have less protection and depth and coolness than they would in the ground.
How Do Plants Know When It’s Fall?
Once more, your plant will use the decreasing light levels, the lowering temperatures, and the different angle of light to detect a change in the seasons.
Your plant will measure the hours of darkness and the hours of light, and know that summer is over.
Plants will usually slow down or even stop growing in the fall, unless you use artificial light to replace the rays of the sun and encourage them to continue.
Check out this article if you’re interested in how to use artificial light to grow houseplants.
Make sure that if your plant has a period of natural dormancy, you don’t interfere with this. Some plants depend on this period for healthy growth and will die if they don’t get it.
In fall, you can afford to put plants closer to the windows again, maximizing what light is still available.
As before, minimize drastic temperature changes, and make sure none of your plants are too close to radiators when you start to heat your home for the impending cold months.
Final thoughts
Houseplants are as aware of the seasons changing as many outdoor plants.
The conditions may be softened by being indoors, but most houseplants can still detect shifts in temperature (especially if they are beside a window) and daylight.
The shifting angle of the light, the fluctuating hours of day and night, and the increasing warmth or cold will all tell your indoor plant that the season is changing.
If you don’t block these signals by keeping plants in temperature controlled rooms with artificial light, they will respond just as outdoor plants would, and grow or stop growing according to their natural patterns
