Preparing Cacti for Cold Weather

Winter is coming which means it’s going to start getting colder and darker (two things cacti don’t like). Protecting your cacti from frost, or ensuring they survive the winter and entering a proper “dormancy” period is essential to avoid abnormal growth. In this blog, we’ll explore the steps you can take to protect your cacti during the cold season, focusing on critical concerns like frost damage, etiolation, and other winter-related issues.

Winter Dormancy

Cactus dormancy during winter is a natural resting phase where cacti slow down their growth and conserve energy. Most Trichocereus enter dormancy in response to cooler temperatures, and lower light. In the United States this will happen in the fall and winter time depending on your locations. 

Observe your plant:

As average temps start to dip below 60°F (~15°C), your cactus will start to enter dormancy, which you’ll notice by observing the following in your plants. You will notice growth start to slow down in your plants. The soil will start to stay wet longer, and your cacti might start to experience some mild etiolation. That means that your cacti are entering dormancy and you need to slow down and stop watering.

Know your Climate + Microclimate

Knowing your specific climate is essential for success, get to know your grow zones and average climates. Anyone in USDA zones lower than 10A will need to consider overwintering to protect their cactus. Challenges when keeping cacti outdoors in the winter without supplemental help

We recommend monitoring the high and low temperatures in your specific growing areas as winter approaches, when the average temperature is less than 60F (15C) then its a good time to stop watering the cactus and begin overwintering. If temperatures frequently dip below 32F (0C) then the cactus must be protected from frost or brought indoors if possible.

We grow in a 9b Zone and have to use greenhouse structures, frost blankets, and heaters, to avoid damaging our plants in this climate, especially in frost events. 

What is a Microclimate? 

Microclimates are also a thing, sun shifts in winter time meaning you may get more shade in some spots, frost settles down hills, wind blows in certain directions, your home is warm and creates insulation for your plants nearby and this all creates a microclimates for your plants in your landscape which you have to consider, test, observe and learn from. Trees and good wind movement can even provide frost protection in the winter time, who woulda thunk! 

It is useful to actually measure the temperature in your own climate with a thermometer. Local forecasts are not specific to your exact location and can be off by several degrees

Keys to Winter Care

The key to winter care is to reduce watering as soon as it gets cold. Cacti can be dry for very long periods of time during the winter…like the whole winter, so just let nature take care of things outdoors and water them. 

Provide frost protection if you're in a zone that dips into freezing temperatures to avoid tip damage. This can be a frost blanket, even a foam cup on top of the growing tip will keep frost from settling. More advanced forms of protection would be greenhouses.

Reduce fertilizing unless you’re continuing to grow indoors or in a greenhouse, and watch out for snails and slugs. They tend to be more active in the winter as soil stays wet longer so treat accordingly.

How to Overwinter your Cactus 

Option 1: Mild Winters

Your cactus might get a little chilly and experience very mild etiolation due to lower light conditions, but this is normal and you can pretty much leave things as-is for the winter. Keep an eye out for any big drops in temp and protect from frost as needed. If indoors ensure your cactus is getting enough light, supplement as needed. If using grow lighting then it will not enter dormancy. 

Option 2: Limited Frost (20-32°F)

You live somewhere where it gets a bit colder from time to time but the cactus can remain alive through the chilly winter (hopefully). Protect the cactus with a frost blanket to protect the tips of the cacti, and keep the cacti completely dry allowing nature to do the watering. Ensure you have ample draining if planted in the ground. If your cactus does get a bit of frost damage it may not die completely it could just get tip damage, causing termination or scarring.  Frost damage isn’t the end of the world, and a cactus can recover, but why damage a plant if we can avoid it.Worst case though is hard frost which roots are wet, they freeze, plant DED. 

Option 3: Severe Winters (below 20°F)

You live somewhere where the temperatures drop to below freezing, or 32°F, for extended periods of time. You will need to move your cacti indoors or inside a greenhouse to avoid harsh damage to your plants. You can then decide if you want to A: let your cacti continue to grow under grow lights normally, or B: have them go into dormancy

To set your cacti up for full dormancy:

1. Make sure the average temperature is below 50°F for a week and stop watering.
2. Bring your cactus indoors into a cold dark space, and stop watering until spring.
3. Bring cactus back out during the spring when temps are not freezing but don’t water yet.
4. Introduce more water as dormancy breaks at around 60°F or you see new growth.

Somewhere cold and dark is recommended, such as a shed or garage. Ensure your cactus remains COMPLETELY DRY, YES COMPLETELY DRY.  Then when Spring comes around you can reintroduce it slowly to the light, water, and warmer temperatures. When temps get over around 60°F the dormancy will break.

Conclusion

Winter may be coming but with a little preparedness you and your cactus will have nothing to fear. Make sure to research your local climate, observe your plants for signs of stress, and take the proper precautions depending on the severity of your colder seasons. With these insights, cacti enthusiasts in various climates can enjoy healthy and beautiful plants year-round, appreciating the unique aesthetic quality and natural growth that these magnificent plants offer.

Key Takeaways

• Cactus dormancy during winter is a natural resting phase where cacti slow down their growth and conserve energy.
• Growth starts to slow down in your plants, soil starts to stay wet longer, and  cacti might start to experience some mild etiolation.
• Reduce watering as soon as it gets cold.
• Provide frost protection if you're in a zone that dips into freezing temperatures to avoid damage to your cacti.
• Reduce fertilizing unless you’re continuing to grow indoors or in a greenhouse, and watch out for snails and slugs.
• If letting your cactus go into full dormancy, place it somewhere cold and dark, such as a shed or garage, and ensure your cactus remains completely dry during this time.