It turns out you can get a lot of sun with the right window angle... but that doesn't work for every houseplant!
Most of my houseplants currently reside on the windowledge of a South-facing bay window, and as the days get longer and sunnier, most of them have been getting too much light. Like me, you might be surprised that this is possible, especially here in the UK and this early in the year - so join me to learn how much light our houseplants actually need - and how to give it to them.
Generally, light is good for plants. It allows them to photosynthesise - meaning the green chlorophyll in their leaves can convert the energy from sunlight to chemical energy to fuel plant growth. It’s an amazing process. But the amount of light a plant needs, and can stand, varies depending on which plant it is. Because every plant has adapted to grow well in a certain place, that is the environment - and the amount of light - it is suited to. And as we head into summer, with our days getting longer than any tropical day ever will, we may discover that, yes, it is possible for a houseplant to have too much light - even in the UK.
Here are some quick stats about daylight in the UK to start us off:
On the summer solstice, the longest day of the year, we get 16 ½ hours of daylight. On the shortest day, the winter solstice, we only get 7 ¾ hours - that’s nearly nine hours’ difference between the two extremes!
On average, we get 4-5 hours of sunlight per day - of course, most of this comes in spring and summer so it isn’t consistent.
This March (2025) was our sunniest and driest on record - with the climate changing as it is, sun-scorched houseplants may get more likely.
When I warn people in the shop that a plant may get too much light, I often get the laughing response, "what - in Britain?" Which I understand - but the answer is yes, actually.
So, how do we choose what to grow as houseplants? Well, a lot of that decision is made by the commercial growers who supply the market. In the Victorian era, tastes were dictated by the latest discoveries to come back from plant hunting - and poaching - expeditions. This is thankfully no longer legal, but our tastes are still influenced by what was popular then.
Nowadays the houseplant market is supplied by greenhouses a little more local than the rainforest. They also take into consideration what plants will survive well indoors. The main differences between indoors and outdoors, especially in the UK, are lower light and more consistent temperature thanks to things like roofs, walls and central heating. Another factor to consider is that mostly, the appeal of houseplants is growing something you wouldn’t necessarily be able to grow outdoors.
Thanks to all of this, we get a range of houseplants from around the world: desert cacti from the Americas; tropical and subtropical plants from rainforests in South America, Asia, Africa and Oceania; succulents from arid parts of Africa. And they all need slightly different levels of light…
Tropical Rainforest Daylight
Unlike in the UK, tropical daylight hours are consistent year round. Every day, the sun is in the sky for about 12 hours - with maybe 20 minutes extra or less around each solstice.
In the rainforest, there is often a lot of cloud cover, so there are on average 4-6 hours of sunlight per day.
Many of the rainforest plants small enough to grow as houseplants grow under the forest canopy - sheltering them from the highest levels of light even on the sunniest days. Think Calatheas, Marantas, Philodendrons and Monsteras - amongst many others!
Daylight for South African Succulents
In South Africa, where many Crassula, Haworthia, Aeoniums and other succulents have their native homes, the longest day is 14 ¼ hours, and the shortest 9 ¾ - still less of a variance than the UK.
Most regions of South Africa average 8-10 hours of sun per day - a lot more than here!
However, many species of succulent plants actually average 6 hours of sun per day, shaded by rocks, shrubbery or trees.
Daylight in the Indochina Subtropical Forests
The solstices show a little more variance than the tropics - here the longest day is 13 ½ hours and the shortest 10 ½.
These areas average, similar to tropical rainforests, 4-6 hours of sun each day.
Again, much of this will be shaded by the forest canopy for the plants that will be our houseplants. Think Hoyas, Chinese Evergreens and Pileas.
Desert Cacti and Desert Daylight
All species of cactus are native to the Americas. In the Mojave desert, the longest day is 14 hours and the shortest about 9 ½.
On average, cacti growing in the Mojave get 12 hours of sun per day (i.e. basically all day, every day)
They do not grow in the shade, either - so your Opuntias, Barrel Cacti and other desert cacti are used to a LOT of sun.
It would be hard to give these plants too much sun in the UK!
You can compare the averages and see that some of these plants are perfectly fine with the amount of light in the UK, and some may not get quite enough for most of the year. But remember, growing indoors adds an extra dimension to the question of light. As we’re talking about the maximum light, I’ll bring you back to my south-facing window…
A British South-facing window
In winter, yes, you will not get much sunlight anywhere - the maximum around the solstice would be 7 ¾ hours and it’s unusual to get such a sunny day in winter - and as we are tilted away from the sun it is not as warm.
However, in summer we are closer to the sun, it’s a lot hotter and we may get up to 16 ½ hours of sunlight - and on some days it may in fact be sunny all day (we live in hope).
Once we get into spring the light may actually start to exceed daily averages for a plant’s natural habitat. In a window, with no shade, facing the sun all day, and with the glass magnifying the heat coming in, many houseplants will get far too warm and sunburnt.
That’s where you need to watch out for your plants getting too much light - and choose carefully what plants can cope with your conditions!
A bay window will get more light than one that’s flush with the wall. Of course the size of the window also affects the amount of light, and how many plants fit on the sill - so even if all of these windows face the same way, there will still be a variety.
On the equator, there is very little change in the amount of daylight on any day of the year. In most tropical areas, it will be no more than 40 minutes different between the two solstices - the longest and shortest day. In the UK, the difference is nearly nine hours.
Think what happens on the first warm, sunny day of summer - we all want to spend as much time in the sun as possible and half the country ends up sunburnt and delirious in a beer garden. Now, we can choose to avoid the sunstroke, wear suncream or wear a hat - but your plants, with only a pane of glass between them and the sun, don’t have that choice. You have to be the one to look after them - so here’s how:
Top tips:
Pick your plants and locations well! A desert cactus will do much better in a south-facing window than something from the rainforest understory.
Be prepared to move your plants around as the seasons change.
Adapt the location if you can’t move the plants - net curtains or fogged-glass window film will shield your plants from some of the sun.
Be aware of which directions your windows face - it is so helpful for houseplant keeping to know where the sun will be, and not just at the times you are usually home.
The shape of your window, proximity of other buildings and the landscape will change the amount of light you get too - so be mindful that your light conditions will be unique to your home.
If you don’t believe me, here’s a couple of photos of the effects of too much sun. Succulents like this Aloe (left) will go red with sun-scorch - you can see its more natural green colour is starting to reappear after it went an alarming shade of red. And you can see the difference in the new and old foliage in the corn plant (right) - the newer, more vibrant leaves in the centre grew after I moved it out of the window’s direct sun - and the older, outer leaves grew when it was getting all that light. You can see they are more dull, with browned and crispy edges, and are generally less healthy. I’m glad I worked out what the problem was and moved it!
You’ll also need to water more in Summer…
As the days get longer and lighter, plants will be able to grow more, and use more energy. This means they’ll be using up water much more quickly than in winter, and additionally, if they are in the sun, it will be drying the soil out too. So make sure you’re ready to up your watering schedule! Top tip if you’re going away and it’s forecast to be sunny at home: move plants away from the window if you can’t get someone to water them. This will help them not get totally dehydrated whilst you aren’t there to help.
To sum all of that up, then you can have too much light for most houseplants. And you can get that in the UK (and apparently in March), so keep an eye on your plants as our days get longer. As I write in April, we are already getting more daylight in a day than any tropical plants would get in their natural habitats, even discounting any canopy shade. Remember that every window will get slightly different light but, while they are all unique, there are some good rules of thumb to follow. And make sure your watering can is ready for more use in summer, too.
And one last piece of advice - make sure you have somewhere suitable to house your plants before you take them home. Because however pretty the plant is, trust me, you will only be more sad if it dies because you didn’t think about where to put it. It’s a mistake we all make, but it is possible to avoid!
Rhianna Bangham
Rhianna works in the shop and contributes to Sprouts of Bristol’s content, including plant care notes, product descriptions, and blog posts. With a degree in Classics, Rhianna’s love for languages – including Latin – is perfect for decoding plant names and adding extra detail to our plant care guides. Outside of work, she enjoys rowing, cycling, and learning the violin. Her favourite plant? The ever-popular Spider Plant, of course!
