Do you have a sun-trap in your home that needs plants? Here’s what to do.
First, let’s check that it’s really sunny. If you have a compass (most iPhones have them in the Utilities or Extras folder, or find an Android app ), check that the windows face south or west. I am a bit ‘directionally confused’, so I stand facing out (towards the window) and look down at the compass), this gives the right result. If they face north or east, you won’t get much direct sun, if any. My front porch faces south west, so is baked when the sun is out and also gets a little bit of sun first thing in the morning because it is basically a box made of upvc.
Then take a look at the glass and curtains; net curtains, patterned or obscured glass (like in a bathroom) will all cut down the sun. Any obstacles outside the windows (buildings, walls, fences) will also cut down the sun, even if they are facing due south. So if you can only see a little bit of sky, there might not be enough hours of sun.
You’ll need to know how cold it gets too. If you have a max/min thermometer that’s great. This records the highest and the lowest temps between resets. Some have a push button reset, some do it automatically every 24 hours. If you don’t you’ll have to guess. Sunny spaces tend to have extremes of temperature; like my porch gets to 40c in the summer sun, and just on 0c at night in the coldest winter (when it was about -10c outside).
If there is no heating, no double glazing and the room doesn’t pick up heat from the rest of the house (like a conservatory, porch, lean-to or greenhouse) we are going to guess that it goes down to about 0c in the winter or possibly lower.
If there is no heating but it picks up some warmth from the rest of the house (a conservatory where you leave the doors open or it is double-glazed) we are going to guess that it goes down to about 5c in the winter.
If there is heating (windowsill, heated conservatory, heated greenhouse) we are going to guess it goes no lower than 15c in the winter.
Now you are the expert in your own home, so if you know different, pick and choose from my recommendations to fit your house.
Cacti: Desert cacti like full sun as a rule. Because the range of temperatures in the desert is huge, most cacti will tolerate temperatures down to just above freezing, as long as they are dry. This means that you mustn’t water them between about October and April. Smaller cacti (seedlings and very young plants – like less than a cm) may not be happy with this, so keep them somewhere a little warmer. Forest cacti (like the Easter Cactus) can’t go this low and don’t like full sun.
Succulents: Most succulents like full sun. But there are exceptions to this ( x Alworthia is one). Look for adaptations to sunny conditions like white hairs, spines, translucent leaf windows, partially underground leaves (like Lithops). Some plants that have succulent stems actually grow better in semi-shade conditions (Rhipsalis is one). They also tend to be less cold-hardy than cacti. So try not to let them dip below 5c, unless you know different.
Pelargoniums: Most will be happy in full sun, and will tolerate temperatures down to 2c if kept dry. They will start to bloom early, and will flower for longer.
Carnivorous plants: These often like full sun, but need a lot of rainwater as well. They have a range of temperature requirements from hardy in the UK to tropical heat. Try Dionaea (Venus fly trap), Drosera (sundews), Sarracenia (pitcher plants).
So don’t just limit your search to cacti; take your list of characteristics (succulence, grey or white colouring or hairs, partially underground stems and spines) and see what you can find. There are exceptions to all guidelines, especially with plants, but the more you look at plants the more you will see.