How to root a cactus cutting

This guide is for cacti that are commonly grown from stem cuttings: columnar cacti such as San Pedro, and branching or clumping cacti. It starts from a cutting whose cut end is already callused (dry and sealed).

The short version

Check that the cut end is callused: dry, hard and sealed.
Set the cut end into dry, gritty cactus mix, just deep enough to stand firmly.
Make sure it cannot rock. Stake it if it does.
Keep it warm and in light shade.
Safest: no water until it roots. Some growers water lightly, which can help but is not necessary (step 7).
When a gentle tug meets resistance, it has rooted. Water lightly, then start normal watering.

In warm conditions most cuttings root in about 4 to 8 weeks. Cooler weather, or conditions that are less than ideal, can take longer, and that is still normal.

What you need

A pot with a drainage hole, a little wider than the cutting
Dry, gritty mix (see "The mix" below)
For a tall or top-heavy cutting only: 3 bamboo stakes and a soft tie, or a handful of stones
Cactus gloves, tongs or folded cardboard for handling the cutting.

Before you start: 3 questions

Which end goes down?

The cut end goes in the soil. Most cuttings are tips, with a single cut end, so there is nothing to decide.

A mid-section cutting has 2 cut ends, and the bottom end, the one that was lower on the plant, goes in the soil. To tell the ends apart, look along the ribs. On some Trichocereus each areole, the small felted pad the spines grow from, sits just below a small notch or crease in the rib, like an eyebrow above an eye, and the eyebrow is on the side toward the top of the plant. Some cuttings are hard to read, even for experienced growers. If you are not sure, email support@thoughtfulpricks.com before you plant it.

Is it warm enough?

Warmth is what drives rooting. Cuttings root reliably when nights stay at about 60 F or warmer. Colder than that, rooting slows or stalls.

If it is warm where you are, start now. If it is cool, you have 2 good options: root it indoors somewhere warm and bright, or keep it dry and out of frost and wait for spring. A callused cutting can wait dry for weeks, and often a few months, but not indefinitely. It slowly uses up its stored water. Neither choice is a mistake.

Pot, or straight into the ground?

A pot is the easier choice, because you control the mix, the water and where it sits.

The ground uses the same method. The difference is that you cannot control the weather, and rain is the main risk, because it wets the cut end before there are roots to use the water. If you plant in the ground:

choose a spot where water drains away quickly, such as a slope or a raised mound, and never a spot that puddles
avoid planting just before a rainy spell, or cover the cutting when rain is forecast until it has rooted
expect cold soil to slow it down, just as it would in a pot

The mix

While a cutting roots, the mix needs to hold it upright, let air reach the cut end, and dry out quickly after any water.

For hot, dry climates: roughly equal parts bagged cactus mix and pumice or perlite. Perlite tends to float to the top when watered. Pumice is nice because it tends to stay evenly mixed through the pot.

For humid or rainy climates: go grittier, about 1 part cactus mix to 2 parts pumice, because the same mix stays wet for much longer in damp air.

What to avoid: peat-heavy potting soil, or anything labeled moisture control or moisture retaining, used on its own. Organic matter can hold water against the cut end for too long and encourage rot.

Water should run straight through the mix.

The steps

1. Check the callus

The cut end should be dry and hard to the touch, sealed across the whole face, and pale, from cream to tan. If it is damp, tacky or soft anywhere, lay or stand the cutting somewhere dry and airy, in bright shade out of direct sun, and check again every few days. If any part of the base is mushy, dark or smells bad, cut back to clean, firm tissue with a clean blade, and let that new face callus before you go on. After your cactus arrives covers the callus in more detail.

2. Prepare the mix

Mix it as above and leave it dry.

3. Choose the pot

Any pot with a real drainage hole will do. A small screen over the hole can help hold in the soil when watering. Choose one only a little wider than the cutting. An oversized pot can hold too much damp mix around the plant. Terracotta dries faster than plastic or glazed pots, which helps in cool or humid conditions. In a hot, dry climate plastic is fine. Square pots are great for saving space, but a square pot holds about a quarter more mix than a round pot of the same width, so choose a slightly smaller one.

4. Set it shallow

Push the cut end into the mix just far enough for the cutting to stand firmly, usually 1 to 3 inches for a 12-inch cutting. Going deeper does not help. It only puts more of the stem in the mix, where it can be more prone to rot. You do not need rooting hormone. Most cacti root without it.

5. Make sure it cannot rock

A cutting that rocks in its pot breaks its new roots as fast as it makes them. Most cuttings about 12 inches long stand firmly on their own in a snug pot and need nothing more. If yours is taller, top-heavy, or still wobbles, support it from the outside with 3 stakes and a loose tie, or pack a ring of stones around the base.

6. Warmth and light

Keep it warm, in light shade: a bright window out of direct midday sun, the dappled shade of a tree, or light shade cloth outdoors. Avoid deep shade, which leads to etiolation: long, weak, pale growth. A cutting that has been in the dark can sunburn in direct sun, so give it several weeks in light shade, then move it into more sun a little at a time. The stronger your sun, the slower you go.

7. Water

The safe default is no water until it has rooted. A cutting with no roots has no way to take water up, and it does not need any. It is living on the water it stored before it was cut, and that store is more than enough to grow roots with. Water it cannot use just sits against the cut end, which is the one part of the plant that is a healing wound. Keeping it dry is the surest way to avoid rot, which is why it is the safest choice and the one to follow whenever you are unsure.

An option some growers use: a light early watering. A little moisture can help new roots along. It is not necessary. A cutting roots without it.

Whether it makes sense depends on your own conditions: is it warm enough and dry enough, and is your mix gritty enough, for the mix to dry out fully again soon afterward? If yes, and the cut end is fully callused and firm, a light watering is an option. Give just enough to dampen the mix, never a soak, and let it dry out completely before you water again. If you are not sure the mix will dry out quickly, skip it.

When growers disagree about early watering, it is usually because they grow in different climates.

8. Wait, and know what to expect

For the first few weeks you will usually see nothing at all, and that is normal. A little wrinkling or shrinking before the cutting roots is normal too, because it is drawing on its stored water.

These are the signs it has rooted:

it stops wobbling, and a gentle tug meets resistance. Keep it gentle, so you do not break the tiny new roots.
any wrinkling fills back out
new growth appears at the top, in a brighter green

Do not dig it up to check. Each look can break the roots it has started.

9. The first watering after rooting

Once it has rooted, give it 1 light watering, not a full soak. New roots are thin and easily overwhelmed. From the next watering on, move to the normal pattern for an established cactus: water deeply, then let the mix dry out before watering again. How often that is depends on your climate, your mix, your pot and the season.

If something looks wrong

What you see	What it usually means	What to do
Base turning brown, black or soft	Rot	Act today. Cut back to clean, firm tissue, let the new face callus fully, and replant in fresh, dry mix.
Wrinkling or shrinking	Normal before rooting; thirst after	Before it roots, leave it alone. After it roots, water it.
Nothing at all after 8 weeks	Usually normal, occasionally too cold	If the base is firm, leave it alone. If its spot is cold, move it somewhere warmer and brighter, and keep it dry.
Leaning or toppling	Top-heavy, or the pot is too loose	Stake it from the outside, or pack stones around the base. Do not bury more of the stem.
Pale or yellow patches facing the sun	Sunburn	Move it to filtered light, then reintroduce sun gradually over several weeks. The scarring is permanent, but the plant usually recovers.