~Cactus Care for Northern Climates~
Often I get asked how to care for non-winter hardy cacti in northern climates when unable to allow them to remain outdoors year round, particularly within the upper mid-west and eastern United States. Hopefully this brief guide will help you maintain your cacti so they enter “dormancy” and avoid winter growth that can cause abnormal and unsightly growth and severe seasonal thickness variations.
The main concern when caring for cacti indoors in northern climate is “etiolation,” the thinning of plant growth due to lack of adequate lighting. Etiolation in leaf plants is shown through lengthy stem growth and a less “bushy” appearance. In cacti etiolation is reflected by thinner growth that often is yellow in color due to low chlorophyll production. This yellow growth can be corrected with a return to higher levels of light in the following season, but the diameter will usually remain thin though stretching outward a bit. With etiolation on a columnar cactus you might have the original growth of a column at 3” and then with severe etiolation you might get 1” growth or less depending on how little light the plant is exposed to. Once you bring the plant back outdoors in the spring the plant will eventually resume the 3” growth and leave the etiolated section as deformity that lessens the aesthetic quality of these beautiful plants. But one must be careful in returning plants to stronger light, especially if etiolated as this yellow area is much more susceptible to “sun burn” which will further scar the plant. Always adjust these particular plants very slowly into strong sunlight, by allowing them to remain in strong diffused sunlight until resuming their normal skin tone. Plants if properly cared for over the winter will not etiolate and will require less acclimatization to full sunlight in the spring (more on this below).
There are two points of import in consideration of cacti, both of which are often misunderstood; the first is that cactus dormancy, a seasonal cessation in growth, is not caused by not watering, or by lowered levels of light, but rather by lower temperatures. Certainly when preparing for dormancy you want to cease watering your plants, but since cacti are adept at storing water for future use a well cared for cactus will without doubt have plenty stored up for continued growth if temperatures allow. The second consideration was mentioned above, and that is that a cactus’ diameter, particularly of columnar cacti, is dependent upon levels of light exposure.
In many cases columnar cacti are sent to more northerly climates from the southwest or southeast United States where they grow quite readily planted in the ground. These plants generally grow to a diameter similar to their natural habitats from South America to the United States. When brought to a more northerly climate they on average grow one to two inches thinner in diameter. Obviously if you are looking to have columnar cactus most closely reflect their natural growth it is important to provide them with high levels of light, but if you can’t do this the beauty of these plants, along with a consistent diameter, can be healthily preserved by avoiding winter etiolation and maintaining a plant under the same lighting conditions season to season.
The stopping of watering in preparation for winter dormancy is important in that along with cessation of plant growth in lower temperatures the plant will also stop root production and the taking up of water. When a plant is not making use of the moisture wet soil is the greatest killer of cacti and causes “root rot.” Of all the causes of cacti death this is the most common and the guilty party of family, friends, and co-workers who with congratulatory aplomb inform you how they can even kill cacti. Root rot attacks the cactus’ roots first and then gradually climbs upwards into the body of the plant, causing it to rot from the inside out. In columnar cactus you can spot the rot early and remove the upper unrotted section and replant come spring, but many globular cacti will rot without notice until all that is left is an empty shell reminiscent of an exoskeleton.
It is important to understand that a cactus is designed to retain water, but without active growth, which is determined by heat, not light, and without transpiration (evaporation of water through the plants skin) the cactus will in most cases need no water for the entire winter season if stored properly. Many cacti can in fact survive for a number of years without water when lacking excessive heat. Always remember that a cactus, without a loss of water (caused by heat and its attending growth), does not require much water. Even if you have cactus sitting on a nice sunning window ledge in winter it will generally not need water for the duration of winter and though it may shrink in appearance slightly and show some wrinkles on the skin will usually survive such signs of dehydration for at least six months, if not even a full year or more, only to be watered later and plump back up to become a fully restored and healthy plant. But remember, even one watering of some cacti without ambient heat to spurn growth can cause root rot. It is far better to not water over winter than to water, at least until you become much more familiar with cacti care and the needs of each particular cactus.
Timing when to cut back on watering to bring into dormancy is important. Generally cacti can remain outdoors until the beginning to end of October depending on your environment and the type of cactus. It might be best to try and keep the soil relatively dry beginning in late September. You may or may not be able to avoid rainwater, but this will be dependent upon the size of your collection in most cases and how easy it will be to pull them under cover to provide protection. For the smaller collections a cheaply made portable and seasonal lean-to or small hoop-house can be easily enough constructed with PVC pipe, wood beams, a few braces, nails, and tape, and clear plastic sheeting. These are well worth the investment to allow your plants to remain outdoors a few weeks longer and provide full protection against rain and moderate protection against frost. For better frost protection in use with your lean-to or hoop-house a bed spread or blanket can be placed over it at night.
Greenhouse plants obviously can have their watering extended due to the maintenance of higher temperatures, but it should be remembered that in more northern climates you will have a precipitous decline in light in the fall and if you keep watering and maintaining high levels of heat the diameter will lessen due to lowered light levels. This may not cause the severe etiolation as often happens when plants are grown indoors, but it can easily cause “pinch marks” at the points between more seasonal growth. Creating the proper environment for your cacti leading up to and during winter can help avoid some of these concerns.
Once temperatures are staying between 50 and 60 Fahrenheit in the day, and falling to the lower 40s or upper 30s at night you might want to consider bringing them indoors to avoid snap freezes that will have you running to protect your plants if they are fully exposed. Generally most cacti will of a certainty stop growing when the daytime temperature is running around 60 degrees. Addressing dormancy at these temperatures is wise until one becomes more accustomed to the climate you reside in and how it affects the sorts of cacti in your collection. As said above, dormancy has to do with temperatures, and not light. But it is important to note again that a plants diameter is dependent on light, and so the less light you have, in combination with adequate heat for growth, will cause etiolation, so it is vital to time the removal of a plant from outdoor lighting to coincide with lower temperature which will cease plant growth. Obviously if you bring a plant into a home at room temperature, and heated over the winter to around 70 degrees, with low light, you are going to get some degree of etiolation as room temperature is generally not cool enough to fully stall growth, therefore it is important to locate an area of your home that might keep the temperatures in the cooler ranges.
In my own case I have an unheated garage that is attached to the home and all my plants go into it. In a prior residence I used an unheated basement. Most of the plants I grow can handle light frost and temperatures slightly below freezing, but I always attempt to get them indoors before this happens and to maintain the garage above freezing. My garage is not well insulated and so it can get down to freezing in severe weather, so I place a thermometer alongside the cacti. If I see the temperature drop below 35 I turn on a small space heater to keep the temperature running around 40 to 45 degrees. Since a full cactus collection could easily die if the furnace goes out due to the lack of electricity, gas, or it breaking, a small kerosene heater might be handy as a backup. People can always go stay somewhere else if this happens, but it is unlikely you would be able to pack up and move an entire cactus collection.
It should be noted that I often will have my cactus in near complete darkness during dormancy. Lighting isn’t necessary for a plant that isn’t in active growth, something you clearly want to avoid during winter dormancy, so feel free to place the plants wherever you are able to provide cool enough temperatures, this regardless of light levels.
Interestingly enough I have even placed year old seedlings in the cold garage for dormancy without much difficulty. Seedlings don’t appear to maintain water during winter storage as well as more mature plants and if they appear too dehydrated I’ll water them and place them under standard fluorescent tubes and on top of reptile heating pads until they plump back up. Once hydrated and the soil dries out completely I’ll remove them back into the garage for storing. What I don’t want them to do though is actually begin to grow as tube lighting isn’t nearly as strong as natural lighting and will cause growth to be too thin. Fluorescent lighting is fine for seed starting (see my Closet Cactus Care), but after the first season or two they should get strong diffused natural sunlight. Stronger illumination can of course be supplied by metal halide or other forms of modern indoor gardening lighting, but generally this isn’t very productive for mature cactus during winter and will often not reproduce the diameter available from sunlight.
Once winter has mostly past, spring nears its arrival, and the chances of severe frost are low, plants can be brought outdoors. With smaller collections plants can be brought out in the day and returned to cover for the colder frost bitten evenings, but with larger collections more care on when to bring outdoors will need to be taken. It is important to acclimatize all plants to sunlight, but particularly important for any plants that might show etiolated yellow winter growth. Be sure not to place any plants into direct sunlight if they remained out of sunlight over the winter. It is best to allow the plants to sit in shade, diffused sunlight, or get just an hour or two of direct sunlight for at least a week to adjust. After this period you can then slowly increase the sunlight for another week or two to about half of that which you intend to eventually have them in at the completion of acclimatization. Following this period feel free to place them into full direct sunlight. If the plants etiolated over the winter then it is best to keep them in strong diffused lighting until the yellow growth resumes its full green hue. If your plants come out in mid-April, like mine do, then be sure to water them with a truly good soaking and then let them alone with just natural rain showers until warmer weather starts to pick up in May. To encourage good growth you can fertilize every few weeks with your standard plant fertilizer made at half strength.
Often I get asked how to care for non-winter hardy cacti in northern climates when unable to allow them to remain outdoors year round, particularly within the upper mid-west and eastern United States. Hopefully this brief guide will help you maintain your cacti so they enter “dormancy” and avoid winter growth that can cause abnormal and unsightly growth and severe seasonal thickness variations.
The main concern when caring for cacti indoors in northern climate is “etiolation,” the thinning of plant growth due to lack of adequate lighting. Etiolation in leaf plants is shown through lengthy stem growth and a less “bushy” appearance. In cacti etiolation is reflected by thinner growth that often is yellow in color due to low chlorophyll production. This yellow growth can be corrected with a return to higher levels of light in the following season, but the diameter will usually remain thin though stretching outward a bit. With etiolation on a columnar cactus you might have the original growth of a column at 3” and then with severe etiolation you might get 1” growth or less depending on how little light the plant is exposed to. Once you bring the plant back outdoors in the spring the plant will eventually resume the 3” growth and leave the etiolated section as deformity that lessens the aesthetic quality of these beautiful plants. But one must be careful in returning plants to stronger light, especially if etiolated as this yellow area is much more susceptible to “sun burn” which will further scar the plant. Always adjust these particular plants very slowly into strong sunlight, by allowing them to remain in strong diffused sunlight until resuming their normal skin tone. Plants if properly cared for over the winter will not etiolate and will require less acclimatization to full sunlight in the spring (more on this below).
There are two points of import in consideration of cacti, both of which are often misunderstood; the first is that cactus dormancy, a seasonal cessation in growth, is not caused by not watering, or by lowered levels of light, but rather by lower temperatures. Certainly when preparing for dormancy you want to cease watering your plants, but since cacti are adept at storing water for future use a well cared for cactus will without doubt have plenty stored up for continued growth if temperatures allow. The second consideration was mentioned above, and that is that a cactus’ diameter, particularly of columnar cacti, is dependent upon levels of light exposure.
In many cases columnar cacti are sent to more northerly climates from the southwest or southeast United States where they grow quite readily planted in the ground. These plants generally grow to a diameter similar to their natural habitats from South America to the United States. When brought to a more northerly climate they on average grow one to two inches thinner in diameter. Obviously if you are looking to have columnar cactus most closely reflect their natural growth it is important to provide them with high levels of light, but if you can’t do this the beauty of these plants, along with a consistent diameter, can be healthily preserved by avoiding winter etiolation and maintaining a plant under the same lighting conditions season to season.
The stopping of watering in preparation for winter dormancy is important in that along with cessation of plant growth in lower temperatures the plant will also stop root production and the taking up of water. When a plant is not making use of the moisture wet soil is the greatest killer of cacti and causes “root rot.” Of all the causes of cacti death this is the most common and the guilty party of family, friends, and co-workers who with congratulatory aplomb inform you how they can even kill cacti. Root rot attacks the cactus’ roots first and then gradually climbs upwards into the body of the plant, causing it to rot from the inside out. In columnar cactus you can spot the rot early and remove the upper unrotted section and replant come spring, but many globular cacti will rot without notice until all that is left is an empty shell reminiscent of an exoskeleton.
It is important to understand that a cactus is designed to retain water, but without active growth, which is determined by heat, not light, and without transpiration (evaporation of water through the plants skin) the cactus will in most cases need no water for the entire winter season if stored properly. Many cacti can in fact survive for a number of years without water when lacking excessive heat. Always remember that a cactus, without a loss of water (caused by heat and its attending growth), does not require much water. Even if you have cactus sitting on a nice sunning window ledge in winter it will generally not need water for the duration of winter and though it may shrink in appearance slightly and show some wrinkles on the skin will usually survive such signs of dehydration for at least six months, if not even a full year or more, only to be watered later and plump back up to become a fully restored and healthy plant. But remember, even one watering of some cacti without ambient heat to spurn growth can cause root rot. It is far better to not water over winter than to water, at least until you become much more familiar with cacti care and the needs of each particular cactus.
Timing when to cut back on watering to bring into dormancy is important. Generally cacti can remain outdoors until the beginning to end of October depending on your environment and the type of cactus. It might be best to try and keep the soil relatively dry beginning in late September. You may or may not be able to avoid rainwater, but this will be dependent upon the size of your collection in most cases and how easy it will be to pull them under cover to provide protection. For the smaller collections a cheaply made portable and seasonal lean-to or small hoop-house can be easily enough constructed with PVC pipe, wood beams, a few braces, nails, and tape, and clear plastic sheeting. These are well worth the investment to allow your plants to remain outdoors a few weeks longer and provide full protection against rain and moderate protection against frost. For better frost protection in use with your lean-to or hoop-house a bed spread or blanket can be placed over it at night.
Greenhouse plants obviously can have their watering extended due to the maintenance of higher temperatures, but it should be remembered that in more northern climates you will have a precipitous decline in light in the fall and if you keep watering and maintaining high levels of heat the diameter will lessen due to lowered light levels. This may not cause the severe etiolation as often happens when plants are grown indoors, but it can easily cause “pinch marks” at the points between more seasonal growth. Creating the proper environment for your cacti leading up to and during winter can help avoid some of these concerns.
Once temperatures are staying between 50 and 60 Fahrenheit in the day, and falling to the lower 40s or upper 30s at night you might want to consider bringing them indoors to avoid snap freezes that will have you running to protect your plants if they are fully exposed. Generally most cacti will of a certainty stop growing when the daytime temperature is running around 60 degrees. Addressing dormancy at these temperatures is wise until one becomes more accustomed to the climate you reside in and how it affects the sorts of cacti in your collection. As said above, dormancy has to do with temperatures, and not light. But it is important to note again that a plants diameter is dependent on light, and so the less light you have, in combination with adequate heat for growth, will cause etiolation, so it is vital to time the removal of a plant from outdoor lighting to coincide with lower temperature which will cease plant growth. Obviously if you bring a plant into a home at room temperature, and heated over the winter to around 70 degrees, with low light, you are going to get some degree of etiolation as room temperature is generally not cool enough to fully stall growth, therefore it is important to locate an area of your home that might keep the temperatures in the cooler ranges.
In my own case I have an unheated garage that is attached to the home and all my plants go into it. In a prior residence I used an unheated basement. Most of the plants I grow can handle light frost and temperatures slightly below freezing, but I always attempt to get them indoors before this happens and to maintain the garage above freezing. My garage is not well insulated and so it can get down to freezing in severe weather, so I place a thermometer alongside the cacti. If I see the temperature drop below 35 I turn on a small space heater to keep the temperature running around 40 to 45 degrees. Since a full cactus collection could easily die if the furnace goes out due to the lack of electricity, gas, or it breaking, a small kerosene heater might be handy as a backup. People can always go stay somewhere else if this happens, but it is unlikely you would be able to pack up and move an entire cactus collection.
It should be noted that I often will have my cactus in near complete darkness during dormancy. Lighting isn’t necessary for a plant that isn’t in active growth, something you clearly want to avoid during winter dormancy, so feel free to place the plants wherever you are able to provide cool enough temperatures, this regardless of light levels.
Interestingly enough I have even placed year old seedlings in the cold garage for dormancy without much difficulty. Seedlings don’t appear to maintain water during winter storage as well as more mature plants and if they appear too dehydrated I’ll water them and place them under standard fluorescent tubes and on top of reptile heating pads until they plump back up. Once hydrated and the soil dries out completely I’ll remove them back into the garage for storing. What I don’t want them to do though is actually begin to grow as tube lighting isn’t nearly as strong as natural lighting and will cause growth to be too thin. Fluorescent lighting is fine for seed starting (see my Closet Cactus Care), but after the first season or two they should get strong diffused natural sunlight. Stronger illumination can of course be supplied by metal halide or other forms of modern indoor gardening lighting, but generally this isn’t very productive for mature cactus during winter and will often not reproduce the diameter available from sunlight.
Once winter has mostly past, spring nears its arrival, and the chances of severe frost are low, plants can be brought outdoors. With smaller collections plants can be brought out in the day and returned to cover for the colder frost bitten evenings, but with larger collections more care on when to bring outdoors will need to be taken. It is important to acclimatize all plants to sunlight, but particularly important for any plants that might show etiolated yellow winter growth. Be sure not to place any plants into direct sunlight if they remained out of sunlight over the winter. It is best to allow the plants to sit in shade, diffused sunlight, or get just an hour or two of direct sunlight for at least a week to adjust. After this period you can then slowly increase the sunlight for another week or two to about half of that which you intend to eventually have them in at the completion of acclimatization. Following this period feel free to place them into full direct sunlight. If the plants etiolated over the winter then it is best to keep them in strong diffused lighting until the yellow growth resumes its full green hue. If your plants come out in mid-April, like mine do, then be sure to water them with a truly good soaking and then let them alone with just natural rain showers until warmer weather starts to pick up in May. To encourage good growth you can fertilize every few weeks with your standard plant fertilizer made at half strength.
