Cacti are fleshy, water-wise succulents in the Cactaceae family native to the deserts of North and South America.
Most are easily distinguished from other succulents by bumps called areoles from which bristles, flowers, roots, spines, and stems grow.
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As houseplants, cacti are generally low maintenance. They require bright, indirect sunlight and watering every few weeks when the soil completely dries out.
This guide discusses when and how to repot a cactus.
Here’s what we’ll cover:
How to Repot Cactus Plants
When to Repot
Cacti grow slowly and like to fit snugly in their containers, but it’s wise to:
- Divide “pups” or baby plants that nestle beside a parent.
- Refresh the growing medium after three years of use.
- Size up the container when the roots begin to creep out of the drainage holes.
- Transplant a new plant from its plastic starter container to a porous one.
Let’s discuss each.
Divide Pups
Some species of cacti produce pups or offsets – clones of the parent plant. As pups develop, they crowd the parent plant, competing for food and moisture in the container.
Our guide to propagating succulents has instructions for separating offshoots from parents and potting them separately.
With the pups removed, a parent plant can remain in its current pot until one of the other conditions indicates it’s time to move into a new one.
Refresh the Medium
A growing medium that sustains a plant for three years or more becomes depleted in quantity and nutrient content. Some organic matter, like peat, becomes more acidic as it ages.
These plants prefer a pH of 6.0 to 6.9 and excess acidity can wreak havoc with nutrients and impair plant health.
Additionally, the potting soil may show signs of being compacted and fail to drain properly.
Repotting into fresh substrate reestablishes a nutrient-dense growing environment and reduces the risk of soilborne pests and disease from taking hold.
Size Up
Fitting snugly in a pot is different from being so tight that the roots wrap around and around and find their way out of the bottom of the container.
An overabundance of roots displaces soil, impairing water and nutrient uptake. Plants may also become top-heavy in their pots and potentially unstable.
The ideal pot is 10 percent wider than the width of the plant and 10 percent deeper than the length of the roots.
To accommodate their shallow roots in the cozy fit they prefer, generally you will need to go up just one pot size.
A container that is too large takes too long to dry out and is likely to promote rotting.
Transplant
A new cactus in a plastic nursery container needs to be transplanted to a porous vessel that promotes air circulation and drainage. Unglazed clay is an ideal material.
If your specimen falls into one or more of the three categories mentioned above, it’s time for a container upgrade.
Because most cacti have sharp spines, it’s best to plan ahead to protect your eyes and skin when working with them.
Collect the following items to make the job easy and injury-free:
- Artist’s Paintbrush
- Eye Protection
- Garden Trowel (Miniature or Full-Size as Needed)
- Long Sleeved Shirt or Gauntlet Gloves
- Nitrile-Coated or Leather Gloves
- Newspaper or Bubble Wrap
- Pruners or Garden Scissors
- Table Knife
- Tongs or Tweezers
- Water
Sanitize metal tools with a solution of nine parts water and one part bleach, rinse, and dry them thoroughly before use.
With your protective gear ready, it’s time to discuss containers and substrates.
Containers and Substrates
As mentioned, the best vessel for a cactus is a porous one that breathes, letting air and moisture through to avoid oversaturation.
Unglazed clay like terra cotta is an excellent choice. See our guide to the best container materials for more information.
Your container should have a generous drainage hole in the bottom, or multiple holes.
Avoid products with attached drip saucers, as they cannot drain excess moisture without tipping and possibly dislodging plants.
The ideal size, as discussed, is 10 percent wider and 10 percent deeper than your plant’s width and height. These succulents have shallow roots that branch horizontally rather than growing straight down.
Sanitize your new or used container before use with a solution of nine parts water to one part bleach, rinse, and dry.
Purchase a quality substrate formulated for cacti and succulents that is loose, well-draining, and not too moisture-retentive.
You’ll want enough to fill your container three-quarters of the way, leaving room at the top for watering without soil overflow.
This product from Hoffman contains compost, peat moss, sand, and limestone to regulate acidity.
Hoffman’s Organic Succulent Soil Mix
Hoffman’s Organic Cactus and Succulent Soil Mix is available from Hoffman’s via Amazon.
Or, follow our instructions to make your own cactus mix with potting soil, coarse sand, and perlite.
With tools, container(s), and growing medium ready, we can get to work.
Unpotting and Repotting
The best time repot your cactus is during the spring-through-fall growing season when recovery and acclimation are most likely to be successful.
If your plant is in bloom, wait for the flower to fade before disturbing it.
With your tools, vessel(s), and growing medium ready, it’s time to prepare your plant to transition from its old growing environment to a new one.
Water two days before repotting so the soil is moist but firm – avoid waterlogging the soil.
Note the depth the cactus sits in its original container. You’ll need to replicate it in the new one. If you like, take a picture for reference.
Wear your protective eyewear, long sleeves (or gauntlets), and gloves.
Fill your new container halfway with fresh growing medium using your garden trowel.
Contrary to popular belief, It is not a good idea to put gravel in the bottom first as this does not promote drainage. Instead, it causes a “perched water table” above the gravel, where water pools, which can promote fungal development and lead to root rot.
To unpot, insert your table knife into the soil against the side of the container and work it around full circle to loosen the contents.
With a new plant, the plastic nursery container may be flexible enough to squeeze a bit and slide the entire contents – soil and plant – out.
You may have to set the container of a well-established specimen on its side to work it off. Here’s where the thick gloves, bubble wrap, newspaper, and tongs are handy.
Because cacti have shallow roots, you never want to grasp the plant and pull as this can end up breaking the roots.
Instead, with the vessel on its side, work the table knife around the soil perimeter again, turning the pot as you go. Use your gloved hands, tongs, and wrappings for gentle support until the contents come free.
Gently remove and discard the old soil, rinsing the roots as needed but taking care not to damage them.
For rootbound plants, use your pruners to cut across the twining roots to encourage new growth.
If the roots are a tangled mess, you can cut up to one-third off the bottom of the root mass before transplanting.
If any roots are dark, malodorous, and/or slimy, they may be rotting from oversaturation.
You can cut off the worst of them, but healthy white roots must be attached for a successful transplant.
Make a newspaper or bubble wrap sling, or use tongs or tweezers to gently grasp the plant while you settle it into the fresh soil.
Backfill until the plant sits at the same depth as it was in the original pot.
Center it upright before firmly tamping the growing medium around it. The vessel should be no more than three-quarters full of substrate to enable you to water without spillover.
Use your artist’s brush to dust off any flecks of soil between the spines, but not so aggressively that you bruise the foliage. Alternatively, rinse with water and avoid returning to bright indirect sunlight until the specimen is thoroughly dry.
Water at the soil level, avoiding the foliage, and place the new vessel in its permanent location in bright, indirect sunlight.
Drain excess water – and don’t let it pool in a drip saucer – to inhibit moisture buildup. Sanitize all tools after use as we did before.
The ideal indoor temperature is between 65°F and 80°F with low humidity. Most healthy homes are in the 30 to 50 percent humidity range.
It’s not necessary to fertilize at planting time, but is beneficial to apply a 15-30-15 (NPK) fertilizer two or three times during the growing season.
In winter, the plants go dormant and stop growing, and fertilizer is not needed during this time.
Water requirements are greatly reduced in winter as well, and the container is likely to remain moist for up to six weeks before completely drying out.
A Contented Cactus
It’s easy to think of cacti as self-sufficient because they grow slowly and don’t need water often.
However, being perpetually in survival mode isn’t good for them. I learned that the hard way when a once adorable mini barrel cactus dry rotted from the bottom up.
Provide bright, indirect sunlight, ample drainage, and loose cactus and succulent soil.
Fertilize during active growth, water when the growing medium dries out, limit water during dormancy, and repot as needed when dividing pups and relieving bound roots.
When you fulfill their cultural requirements, these plants don’t just survive life as houseplants, they thrive.
What are your tips for repotting cacti? Please share them in the comments section below.
And for more information about growing cacti, check out these guides next:
