These slow-growing, desert-loving American natives are hard to miss, thanks to an armour of prickly spines. These spines are in fact leaves that have evolved to defend the cactus from thirsty desert animals. They also act as catching points for dew drops. Some cacti have so many spines, they also serve as shade. Some cactus also feature satiny flowers, which although short lived, are very beautiful, appearing in every colour except blue.
When do I water my cactus?
Cacti have a built-in tolerance of extreme drought, leading many to believe they don’t need a lot of water. While it’s true they're tough, most cacti won’t thrive without water.
That said, overwatering is where many go wrong. Too much water encourages botrytis fungus to rot the roots and base of the plant. Once botrytis fungus has taken hold, even a strong fungicide won’t save it.
Whether you keep your cactus indoors or out, the general rule is to let the soil dry out completely before watering it again. When watering, give the soil a good soaking, so that water runs out of the drainage holes (if your cactus is in a pot). In autumn and winter, cacti take a nap. During this time, water less often and again, let the soil dry out between watering.
Do cactus need a lot of sunlight?
Yes! Cacti love bright light. A cactus that’s enjoying ideal light conditions will look normal and is more likely to flower.
But not all cacti tolerate intense, direct sunlight, especially when the temperature is high. If your cactus appears off colour, bleached or is turning yellow or orange it may be getting too much light. Bear in mind these signs can also indicate disease or too much water, so use your judgement.
While it’s normal for a plant to slowly grow toward light, if your cactus is bent at a right angle toward the light, it may be time to move it to a brighter spot. Make the move gradually to avoid scorching and scarring.
For indoor-dwelling cacti, place it in a bright spot, like a window sill. Give it as much sun and fresh air as you can and remember, all indoor cacti benefit from a holiday outdoors.
When should I feed my cactus?
To encourage growth and flowering, in spring and summer feed your cactus regularly with a balanced fertiliser (one with equal proportions of nitrogen, phosphorous and potassium diluted to 1/4 strength) each time you water it.
Cacti in pots
Like succulents, terracotta pots are best for cacti as they allow the soil to dry out faster, however cacti will grow in most pots, so take your pick. Whatever you choose, make sure the pot has good drainage. If you find a pot that’s perfect but doesn’t have drainage holes, drill them yourself. Plastic pots are lighter and easy to keep clean. Cactus kept in plastic pots also tend to need less watering. If your cacti is tall or top-heavy, the extra weight of a clay or ceramic pot will provide stability. If you’re wondering how to repot your cactus, handy tools can include newspaper, paper towels or foam rubber.
Best soil for cacti
Your cactus' soil must be well-draining. You can buy special cactus potting mix or create your own mix of coarse sand, crushed sandstone, fine gravel and compost or coir peat. Mulch your cactus with gravel to keep its collar dry.
Common cacti pests
Dab these tiny cottony-covered insects with a cotton swab dipped in rubbing alcohol. For a widespread mealybug attack, try a systemic insecticide. If you can’t see any mealybug on a cactus that appears sick, root mealies might be to blame. To eliminate, unpot the plant and if you find unwanted guests, wash off as much of the soil and bugs as possible, soak the roots in a systemic insecticide and repot.
Scale are miniscule insects that appear as raised tan or brown spots and dine on plant sap and can be treated similarly to mealybug infestations.
Spider mites are almost invisible. Infected plants often develop yellowish spots which later turn rusty brown, scarring the plant. As both cacti and spider mites hate being wet, try overhead watering or misting.