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There are over 2000 different types of cacti. I’m not doing 2000 different posts on how to care for each of them, but this care guide will be suitable for the majority of common cacti available in the shops.
If you spend a lot of money on a weird one, please research that specific species. We’re doing general stuff here. I’m not being held responsible for you only fertilising your cactus once a year when that particular type needs fertilising twice a day.
I’m just trying to help all you plant killers to keep ONE species alive, and cacti are the one to try. So on we go.
- Light: bright
- Humidity: lower rather than higher, but generally not fussy
- Temperature: summer: 18C/65F – 32C/90F winter: 7C/45F – 12C/55F
- Watering: infrequent, tap water is fine
- Fertilising: 5-10-10 every 2 months in the growing season
- Potting medium: cactus mix
- Propagation: stem cuttings, seeds, offsets, grafting
- Pests: mealybugs, scale, spider mites, aphids, thrips
- Bloom? yes, if they’re given cooler temperatures
- Toxic? not usually, but spiky nonetheless
The word cactus actually means ‘spiny one of uncertain origin’ in Ancient Greek.
Cacti are almost all succulents, which broadly means that they have the ability to store water. Cool cool cool.
They come in all shapes and sizes, from 1cm tall to nearly 20 feet (that’s the Elephant cactus. Google it, it’s incredible).
Cacti are found in many parts of the world, and though they can live in some of the driest parts of the world, they don’t all live in deserts. Some can be found in tropical rainforests, for example, Rhipsalis, which is an epiphyte (it grows by attaching its roots to trees, rather than in the ground) cactus.
Cacti would most like to live on the windowsill of a south or west-facing window, please. Don’t stick ’em on a dingy shelf or, god forbid, in the bathroom.
Cacti can handle a lot of bright, indirect light, and can tolerate a decent amount of full sun. I keep mine on west-facing windowsills and, so far, they’ve not burned.
(Remember that I live in the UK though – there’s barely enough sun to burn me, never mind a cactus).
In winter they need less light, but since the days are so much shorter I keep mine where they are.
Desert cacti can withstand huge variations in temperature. Here in the UK, I don’t need to worry about it getting too warm, but if you live in a hot climate they’ll be fine as long as they get enough water.
It is thought that in order for cacti to bloom they need a sharp drop in temperature. I’m not sure if they actually go dormant but growth certainly slows.
Unlike most other house plants, I’m happy to leave my cacti on my living room windowsill. Other plants would freeze because the space between the glass and the curtain creates a little pocket of cold air. The cacti are unfussed by the cold – so long as they stay dry.
Unfussy. Cacti and succulents are great at tolerating dry air (they manage to grow in the Atacama desert for Christ’s sake), but they also don’t seem to suffer in quite high humidity.
I know this, because my house is a naturally damp 68% humidity at the mo, and the cacti are fine.
Repeat after me:
Water your fucking cactus.
Cacti have a reputation for not needing much water, and it’s BOLLOCKS. By ‘not much water’ some people think watering once a year is adequate. NO.
Get yourself a moisture metre if you don’t believe me. In summer mine get watered almost weekly.
However, there are some caveats when it comes to watering your cactus:
- Only water it when the soil is dry. We’re talking 1 on a moisture metre.
- Bottom water if you can, but if you can’t, try to avoid getting water on the plant – they can rot easily.
- Water it thoroughly. Don’t just give it a little trickle. Water thoroughly until the water is running through the drainage hole. If I’m bottom watering I let cacti sit in the water for an hour or so.
- Whilst most commercially grown cacti are used to tap water, use rainwater if you can since some species are prone to root burn from salt build-up. Research your specific cactus type if you’re worried.
After a lot of googling, I’ve learnt that there’s a lot of different opinions on whether or not you need to fertilise cacti.
I would tend to go with Gardening Knowhow‘s recommendation – they say a good 5-10-5 or 5-10-10 (more phosphorus than nitrogen) fertiliser, diluted to half, will keep your cacti happy.
Gardening Knowhow also says that fertilising your cactus annually is probably enough, though 2-3 times a year is optimal.
Over fertilising is extremely harmful to cacti, so if in doubt, leave it alone.
Honestly, I buy special pre-made cactus and bonsai potting mix.
What’s important is that the mix is extremely well-draining. A mix of equal parts potting soil, washed sand, and gravel or pot shards will work too. You can add Perlite or pumice too if you happen to have some.
But yeah, there’s nothing wrong AT ALL with pre-mixed cactus potting mix.
I favour terracotta for cacti because they like a big drink and then to dry out quickly. Some cacti growers actually blow-dry their cacti after watering them to keep them in optimal condition.
I can’t imagine keeping your cactus in the nursery pot or in a ceramic pot would do it any harm as long as you don’t give it either too much water or not enough light.
A lot of the information on cacti I found recommends repotting cacti as soon as you bring them home, in case the potting mix is unsuitable.
I’ve personally never bought a cactus that was in anything other than specific cactus mix BUT I suppose it depends where you get your plant from. All my cacti are from garden centres, but if you get yours from e.g. the supermarket, check it’s in well-draining soil.
Fuckin’ mealybugs. They seem to LOVE cacti, I’m guessing because they’re nice and moist (sorry) on the inside.
They can also get scale, spider mites, thrips, and aphids.
Wow, the full set.
What I can personally attest to, is that cacti don’t seem to give a shit if they have pests. One of my cacti has had mealybugs for…a while (like a couple of years, sorry) and it seems unmoved. It has a bit of scarring, but it’s growing and blooming and having a nice time.
I’ve since eradicated the mealybugs by spraying the affected plant with a mixture of water, neem oil and dish soap. It works, provided you remember to do it every few days for a couple of weeks.
Fingers crossed, I’ve not encountered any other critters on my cacti.
Oh, and if you have a substantial cactus that you think can take it, a good hose down outside can blast off a few bugs. Just don’t leave it outside too long in case it picks up new bugs.
I’ve never actually tried to propagate a cactus, but it seems simple enough.
You can callously lop the top off your cactus and it’ll root, apparently. I haven’t tried it, mainly because mine are all too spiky. You just cut a bit off with sterilised tools, let the cut callous over for a few days and pot in up, with about a third of the cutting in the soil. Keep the soil damp but not wet by misting it, and it should root within a few weeks.
You can also cut off those little offshoots some cacti produce, which seems a lot less dramatic.
It’s also possible to propagate cacti from seeds, though the process is long and slow.
If you want to try propagating by grafting, you’ll have to google it. It’s way too high level for me. Looks cool as hell though.
Be kind. Some of them have had a very hard life.
- Cacti are not, contrary to popular belief, impossible to kill. I know this because my mother has killed several.
- Cactus blooms are delicate and beautiful and amazing. Check out my Instagram to see mine.
- Some types of cacti produce edible fruit
- Some really swell dudes are making leather from cacti
- Oven mitts are great for handing cacti, but make sure you have a pair for cacti use exclusively, and don’t put them through the washing machine. Let me make that mistake for both of us.
To be perfectly honest, I’m not a massive cactus fan. I’ve never actually bought one – mine are my boyfriend’s that I’ve taken over the care for, since he’s prone to casual neglect.
They’re too spiky. They hurt. They also grow MASSIVE which would be cool if only they weren’t so spiky.
I’m sorry cacti. I’ll still care for you as well as I can.
4 thoughts on “Plant profile: how to care for…cacti”
Hi! Suggestions as to why my fishhook cactus (?) is going soft at the top? I water it in summer once a month thoroughly, in winter maybe every three months. It has lots of indirect sun and maybe two hours of late afternoon direct sun. It had a grow spurt this summer since moved it closer to the window and had to turn it regularly since the top is bending to the window. Originally I thought it was because the top moved to the light all the time and it grew quite quickly, but now I notice the softness spreads slowly to the sturdy base (noooooooooooo!!). There is no root rot, no discernible bugs, no discolouring, no oozing, no mould. Reading your article it might be too little water..? But would that affect problems from the top? Should I just cut it off (oh my poor baby!)?
I know it’s hard to tell from description, but I will be grateful for any suggestion! Thanks!
Can you increase the light a bit? That’s usually a great way to help cacti, even if it doesn’t address the root of the issue.
It does sound like root rot or possibly high humidity BUT my ponytail palm goes mushy like that when it’s under watered, so you might be right – especially since root rot is usually accompanied by discolouration.
Could the soil be hydrophobic? Try bottom watering to make sure the soil is actually getting to the roots.
Hi Caroline! Quick follow up – I’m extremely afraid of overwatering 🙂 A good soak helped the cactus immensely! Thank you!
Yay, I’m so glad!
I watched a programme once about professional cactus growers and they water their plants quite often (like, weekly) but then use a blow dryer-type thing to dry the soil out after. Apparently the frequent watering encourages fast growth and the drying out of the soil stops root rot. I need to try to get one of these soil dryer-out things and review it!