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Preparing Fast-growing Columnar Cacti for Winter Dormancy

Many cacti growers are curious about the proper way to prepare their cacti for winter. Others may not even know that they need to make any changes at all. In this guide, we will discuss the reasons for cacti dormancy and how to properly prepare your cacti for dormancy.

When an oak tree loses its leaves in the winter and ceases growing, it is dormant. Likewise, cacti also experience dormancy when certain conditions for growth do not meet the requirements needed for it. Preparing cacti for dormancy is especially important for fast-growing ornamental columnar cacti such a San Pedro Cactus or a Cereus Peruvianus. If growers do not prepare in advance, the aesthetic appeal of their cacti will suffer.

Cacti dormancy is triggered by a drop in temperatures. For some people, preparing cacti for winter is limited to bringing their collection indoors. In climates that permit cacti to be left outdoors all year round, they will experience a temperature drop and cease growth. After you bring your cacti indoors, unless you keep your house rather cool, your cacti will never receive the message that winter is here and will not completely enter dormancy. While it might seem alright to have your cacti skip dormancy and grow year round, it comes with a price.

During the winter, you may gain some height, bit it will not be they type you want. The problem is that you will not have enough light in your house. Even with the best grow lights, it is unlikely that you will match the power of the sun. And since cacti thickness is dependent on the amount of light it receives, your cacti will suffer uneven growth. While stretching may not be such a significant problem with slower-growing cacti such as ariocarpus or lophophora, a tirchocereus will respond quicker and stretch.

The process of stretching in low light conditions is called etoliation. Etiolation occurs because the cactus is trying to reach up in an effort to find light. It is recognizable by a very light green color. Severe etiolation, such as when a cactus has been in a box, can even result in white growth. Even with proper preparation, you will usually notice a bit of this color at the tip of your cacti. The key is to minimize this to keep growth uniform. As the cactus resumes growth the following season, small amounts of etiolation will be covered up. You can often tell how many seasons a cactus has been growing by the ridges formed as this cycles occurs. Some growers play around with etiolation to create oddball cacti. An etiolated cactus is not necessarily unhealthy, but it can create weak points if you plan on growing tall specimens.

So how do we prevent etiolation? The key to preventing etiolation is to keep your cacti in a very cool place until you can return it to the outdoors. Most growers accomplish this in a cool basement or garage. A temperature in the low 50’s to high 40’s is ideal. Be sure to keep your cacti out of freezing temperatures, although larger cacti can handle brief stints of temperatures on the border of 32 degrees F. It is also important to note that dormant cacti do not require light since they are asleep. This makes storage easy, allowing you to reserve your light for other plants.

While this seems easy enough, your preparation should actually begin well in advance. This is because dormant cacti will not need water during the winter. While cacti are in dormancy, their immune systems are diminished. The presence of water they are not using gives disease a chance to gain a foothold. Unless your cacti are seedlings, you should NEVER water them during the winter dormancy period. Seedlings should not be put into dormancy because they would not normally begin growing so close to winter. It is not natural for them. Furthermore, artificial lights can accommodate the full requirements for seedling growth.

Despite that you may not be actively watering your cacti, they may still be at risk. Your cacti may be in large pots with lots of soil that can hold lots of water. Therefore, it is a good idea to ensure that your soil is dried out before the temperature drop. Begin by moving your plants to a covered location, such as an awning, sometime in September or October at the latest. This will allow the plants to dry without the rain interfering. By the time you bring your plants in, they should be dry enough. Use the natural cooling of the weather to induce dormancy naturally, then maintain that coolness.

While the concept of dormancy may seem complicated to some, the solution is anything but. Keep your plants cool and dry. Let the soil begin drying out in advance. The amount of light you provide is insignificant. So you might as well let them sleep in the dark.