We grow in Fallbrook, California, zone 10a, so the real education has come from the plants we ship out. Every September we hear from people in Ohio, Georgia, and Colorado deciding what to leave out and what to carry in, and the pattern never changes. Almost nobody loses a plant to cold alone. They lose it to cold plus water.
What does cold hardy actually mean?
A USDA zone is one number: the average annual lowest winter temperature where you live, sorted into 10 degree bands. Zone 5 averages a low of -20F to -10F. Zone 7 is 0F to 10F. Zone 9 is 20F to 30F. Each step up buys another 10 degrees of mercy. Look yours up by zip code on the USDA map before you buy anything that has to live outdoors. It takes ten seconds and it saves plants.
Now the part the tag does not tell you. A cactus freezes the way a water balloon does. Water inside the tissue expands into ice, ruptures the cells, and the plant turns to mush on the thaw. A plant that goes into winter dry has far less water in it to freeze, which is why the same species is rock solid at 10F in Arizona and dead at 28F in Alabama. Most hardiness numbers online were written by people gardening in the dry version.
Duration matters too. When a rating says a plant tolerates 15F, that means briefly, an overnight dip that burns off by mid morning. It does not mean three weeks of frozen ground. If your lows sit rather than spike, drop every rating a zone.
What survives winter in your zone?
The honest tier list, built from plants we sell. Every temperature assumes dry roots and a brief dip, not a long freeze.
Zone 3 and 4, to about -40F
- Hens and chicks, Sempervivum tectorum, zone 3. The toughest plant in this article. It sits under snow all winter and greens up in spring.
- No true cactus is reliable this far north without a cover.
Zone 5 and 6, about -20F to 0F
- Claret cup hedgehog, Echinocereus triglochidiatus, about -20F. A clumping hedgehog with red cup shaped flowers, and the genuine cold hardy cactus here.
- Cobweb hens and chicks, zone 5.
- Shop zone 5 and zone 6.
Zone 7, about 0F to 10F
- Artichoke agave, Agave parryi, about 0F. A tight gray blue rosette, and the anchor plant for this zone.
- Everything in the colder tiers works here too.
- Shop zone 7.
Zone 8, about 10F to 20F
- Santa Rita prickly pear, about 10F, worth growing for the purple winter pads alone.
- Candelilla, Euphorbia antisyphilitica, a fine stemmed pencil bush.
- Variegated century plant.
- Shop zone 8.
Zone 9, light frost only, about 20F to 25F briefly
- Golden barrel, San Pedro, Mexican fence post, and Argentine saguaro, Trichocereus terscheckii, one of the hardier columns at about 20F.
- These live outside year round in Fallbrook with no cover. Anywhere colder they need a cover on freeze nights, or a trip indoors.
- Shop zone 9.
Zone 10 and warmer, no frost at all
- Blue torch, totem pole, and most of the soft tropical succulents.
- North of zone 10 these are houseplants that summer outside, full stop. Do not try to winter a blue torch in the ground in zone 8. We have watched people try.
How do you get a cactus through winter outdoors?
Site the plant right and you buy close to a whole zone of tolerance for free.
The outdoor winter setup
- Plant on a slope or a raised mound. Never a low spot where water collects. Six inches of mound lifts the roots above standing water, and it is the highest impact item here.
- Grit, and more of it than you think. Half pumice, decomposed granite, or coarse sand worked in deeper than the root ball. Clay holds water against roots for weeks, so on clay you mound and amend or you do not plant. See our soil guide.
- Put it against a south or west facing wall. Masonry soaks up sun all day and gives it back overnight, and those few degrees are often the whole margin. See the light guide.
- Cover for wet cold, not just cold. A cloche, an upturned bucket, or a clear panel propped over the plant keeps rain and snowmelt off the crown. You are blocking water more than air.
- Stop watering in late fall. Not a reduced schedule, effectively none until spring growth starts. Winter rain is already more than the plant wants.
- Mulch with gravel, never bark. Bark holds moisture right where the stem meets the soil, which is where rot starts. Gravel drains.
When should you bring a cactus inside?
Bring it in when the forecast low drops below the plant's rating, and for anything in the zone 9 or 10 tier, for any hard freeze at all. If it is already potted, moving it beats protecting it where it stands.
Inside, the plant wants a bright south facing window and nothing else. Cool is better, not worse: 50F to 60F suits a dormant cactus more than a warm living room. Keep it off heater vents, which dry it out and coax weak pale growth at the worst time of year.
Do not water it. A dormant cactus in a cool room can go the whole winter without a drink, and that is not neglect, that is the plan. In spring, move it back outdoors over a week or two starting in shade, because a plant that wintered on a windowsill will scorch in direct March sun on day one. Our watering guide covers restarting, and your cactus knows what to do this winter has more seasonal detail.
What kills cacti in winter?
Four things, in the order we hear about them.
Cold plus wet
- Wet roots in freezing soil. The plant looks fine in February and collapses into a soft brown mess the week it warms up.
- That is rot, not frost damage. The fix is drainage and a rain cover, not a warmer spot. See yellow, brown, or mushy.
A pot freezing and thawing
- Soil in a container freezes solid where ground soil would not, and repeated freeze thaw cycles tear roots apart. Pots crack too.
- Potted plant in a cold zone, it comes inside. Our repotting guide has the safe way to lift one.
A warm window and a cold night
- A cactus pressed to single pane glass bakes at 80F in afternoon sun, then sits at 35F against that same glass overnight.
- Pull it a few inches off the window and the swing mostly goes away.
Watering because it looks thirsty
- In winter it always looks thirsty. That is the point. A shriveled cactus in January is a healthy cactus.
- The rule does not change with the season. Soak and dry, water only when the mix is completely dry through, which in winter means basically not at all.
- Overwatering is the number one killer we see, and December is when it does its best work. When in doubt, wait.
Which succulents are cold hardy?
Two groups are the genuine article. The rest of the succulent aisle is bluffing.
Actually hardy
- Sempervivum, the hens and chicks, to about -40F in zone 3.
- Hardy Sedum, the low creeping stonecrops, in the same range.
- Both are alpine plants that evolved under mountain snow, which insulates the crown. They are why hardy succulents is a real category and not just a label.
Not hardy, whatever the tag says
- Echeveria, Kalanchoe, Crassula including jade, and most Aloe.
- The pretty rosettes and fat leaved plants people fill pots with. They go to mush around 30F to 32F, sometimes at the first frost.
- Every one comes inside. Aloe vera gets left out constantly because it looks tough. It is not.
If you want one plant that ends the argument, buy hens and chicks. They multiply on their own and will outlive several of your other gardening decisions. Browse the succulents, the agaves, or all cacti.
The quick version
- Most cacti are not cold hardy. A few genuinely are, and hardiness is temperature and water together. Wet cold kills 20 degrees warmer than dry cold.
- Look up your USDA zone by zip code, then shop one zone colder if your winters are wet or snowy.
- Zone 3 to 4: hens and chicks. Zone 5 to 6: claret cup hedgehog. Zone 7: Agave parryi. Zone 8: Santa Rita prickly pear. Zone 9: golden barrel and San Pedro. Zone 10: blue torch, indoors anywhere colder.
- Outdoors: slope or mound, gritty soil, a south or west wall, gravel mulch, a cover against winter rain.
- No water from late fall until spring growth. Soak and dry, which in winter means basically none.
- Indoors: bright window, 50F to 60F, off the heater, no water, then back outside gradually in spring.
- Shriveled and purple in January is normal. Soft and brown is rot.
- Hardy succulents: Sempervivum and hardy Sedum. Not hardy: Echeveria, Kalanchoe, Crassula, Aloe.