Living SoilHas a cactus or succulent ever collapsed on you, soft and yellow at the base, when you thought you were looking after it well? Often it is not neglect at all. It is kindness: too much water, in a soil that holds it.
Cacti and succulents are desert plants. Give them a soil that stays wet, and excess water can rot them in a very short time. So the whole job of a cactus soil comes down to one thing.
Drainage first, everything else second
A cactus and succulent mix is designed to drain fast and dry out completely between waterings. Cacti and succulents do not need as much humus as other plants, and a high proportion of sand should be present.
A good mix has two parts doing two jobs:
- A mineral part: perlite, coarse sand, pumice or fine gravel. This creates the large pores that let water drain and air return to the roots quickly.
- An organic part: potting soil, pine bark, compost or coir. This holds a little water and a little nutrition.
The mineral part has to win. How much of each is the recipe, and the references give more than one, which is why Living Soil shows each with the reference behind it.
Two mistakes that make drainage worse
Play sand
Sand sounds like the obvious desert ingredient, but the wrong sand backfires. Fine play sand fills the gaps between larger particles and makes drainage worse. Use coarse sand, or skip sand and use perlite or pumice.
A gravel layer in the bottom
It is an old habit: a layer of gravel at the bottom of the pot "for drainage". It does not work. A gravel layer slows drainage rather than helping it, and it is no substitute for a drainage hole. Every cactus pot must have one.
Watering: the real killer
The most common mistake with cacti and succulents is not the soil. It is watering on a schedule instead of watching the soil, especially in the low light of winter. Excess water trapped in the soil can cause rot in a very short time. The signs are yellowing, soft stems and collapse.
The rule from the research: water thoroughly, until it drains out of the bottom, then let the soil dry completely before you water again. That is typically every 2 to 3 weeks, but your conditions decide, not the calendar.
And go easy on food. Do not feed in winter at all.
What pH?
Here is an honest answer you will not see on many plant tags: no cactus specific pH was found in the published sources. The general potting target applies, 5.5 to 6.0 for soilless mixes and 6.0 to 6.5 for mixes that contain soil. Anyone quoting a tighter cactus pH is guessing.
Find the mix for your plant
Agave, aloe, echeveria, haworthia, jade: they all share the drainage rule, but they are not identical. Look up yours in cactus and desert succulents to see its guide and the mixes that suit it.