The Ultimate Guide to Potting Columnar Cactus
Everything you want to know about potting a columnar cactus like Echinopsis Pachanoi (San Pedro), Carnegia Gigantea (Saguaro) or Echinopsis Peruvianus (Peruvian Torch).
What type of pot to use
There is an ongoing debate in the cactus community over what post is best for our spiky friends: Terracotta, Glazed or Plastic. Here’s a quick summary of the debate:
Terracotta
Pros: looks great, is fairly cheap, has a “wicking” quality that assists with drainage, good for the environment.
Cons: heavy especially when watered, fragile, in summer/very hot places (like most of Australia) the wicking quality isn’t actually ideal, in the sun the pot gets hot which can burn roots.
Glazed or “sealed” terracotta
Pros: looks great, doesn’t wick which is mostly a pro in Australia, a wide range of colours and shapes to choose from, good for the environment.
Cons: heavy, quite expensive, fragile, in the sun the pot gets hot which can burn roots.
Plastic
Pros: considerably cheaper, don’t weigh much which makes them suitable for shelves, doesn’t wick which is mostly a pro in Australia, a wide range of colours and shapes to choose from, easy to add more drainage if needed.
Cons: not as attractive as other option, not as good for the environment.
Consensus: unless you live in an unusually cold part of Australia we recommend avoiding Terracotta due to its wicking qualities. Glazed or “sealed” terracotta, are good options if they are in your budget, but plastic works fine too.
Despite their differences, everyone can agree on one thing - your pot absolutely needs to have good drainage i.e. holes on the bottom of your pot.
What size of pot to use
Ideally we want a pot that your cactus will be happy in for at least 2 growing seasons/years. Cactus are incredibly tough plants, but their weakness lies beneath the surface in their root systems. No matter how careful you are, whenever you repot a plant you will damage/shock it’s roots and for cactus this is particularly upsetting, so we want to keep repotting to a minimum over it’s lifetime, whilst still also having it in a pot that is not too large for it.
Width
Our cactus cuttings are taken from large, mature plants and are therefore quite thick compared to seed grown plants of a similar height. We also recommend the use of large rocks in the pot, which we will explain in the next section, so for that reason we usually recommend quite a large pot, with at least least 10cm of space on all sides of the cactus, preferably 15cm. Taking into account the width of the cactus (usually around 10-15cm), this means a pot which is about 30-40cm wide. For our large cuttings you may want to use a 50cm wide pot.
Height
Try and find a pot which is roughly the same height as it’s width. It can be a little different, but try and avoid very deep or shallow pots. Tall pots can create drainage issues, and there is an unnecessary amount of soil to use. Shallow pots will become root bound too quickly, which we’d like to avoid.
Using Structural Rocks in Your Pot
You’ve got your rooted cactus, your pot of choice and your homemade cactus soil mixture, great, it’s time to pot up! But first, let’s go find a couple of nice big, flat rocks.
Most people know that cactus grow in rocky areas, but did you know that it’s because they actually eat the rocks?
Well, sort of. They have a symbiotic relationship with bacteria that lives on their roots which breaks down the rocks into essential minerals and trades them with the cactus through its roots for water. Pretty neat, huh?
They also use large rocks like anchors, wrapping their roots around them so they don’t tip in strong winds.
Whilst simulating this in a potted environment isn’t absolutely necessary, doing so will promote exceptionally good root growth which is the most important thing for healthy cacti. It also looks great!
We have touched on this before in Cactus Soil 101, but a great resource to know more about this is The Stone Eaters.
What Kind Of Rocks to Use
You want to try and find 2 or 3 relatively flat rocks that are a little bit longer then your pot, so when you place them in the pot they protrude by about 5cm.
Most rock types will work for this purpose so long as they are coarse and not smooth like river rocks.
Sandstone is a great option but can be hard to come by, avoid limestone as it alters the soil PH.
How To Pot Like a Pro
What You’ll Need:
Gloves;
A suitable pot;
2-3 long, flat rocks.
Potting Instructions
Thoroughly soak the perlite-potted rooted cactus cutting, you want to make sure all the roots are damp;
Set it aside;
Take your bucket/container of cactus soil mixture and add water until it is damp, but not soggy;
Fill your pot a few cm’s deep with the damp cactus soil;
Take your rocks and place them in a V shape in the pot to create a cradle;
Add more cactus soil until you are confident it is a suitable depth for your size cactus and pot. Your cactus should only be buried deep enough to have stability;
Carefully remove your rooted cactus cutting from the perlite and place it between the two rocks;
Fill the remaining space in the pot with damp cactus soil;
Lightly flatten the top of the soil, but avoid pushing down too much. You don’t want to compact the soil and make it difficult for the roots to adjust to the new, already denser medium;
Place the cactus back in the same place it was rooting;
Leave it to settle into its new home for a week or two before moving into the sun.
