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Cactus Care



   General Care for Cacti and Other Succulents



     Growing Succulents:
   the basic principles.


  
Cactus and other succulent plants are easy to grow, and are non-demanding. They are highly drought tolerant, and do not require a lot of regular maintenance: most require less frequent fertilization, repotting and "grooming" than typical foliage plants, and (at least in my experience) are generally more resistant to insect infestations than other types of house plants as well.

       Keep in mind that cacti and other succulents are remarkably diverse and widespread plants. There are tens of thousands of species, varieties, and hybrids of succulent plants; different plants may be adapted to very different climates. A few species occur well into artic regions and will tolerate temperatures to below -50 degrees Fahrenheit, some species are adapted to the hottest regions in the world and may survive temperatures to 130 degrees or more. Some species are adapted to some of the most arid deserts on Earth, sometimes going several years without significant rain, while others are adapted to rainforest conditions, and will tolerate seasonal monsoons. No single set of guidelines will apply to all of these plants, but attention to a few very basic rules of thumb will assure good growth in the majority of them.

    As a rule, cactus and other succulents are adapted to conditions of:

    

     
1. Bright light.

      2. Periodic to frequent drought

      3. Warm temperatures

      4. Fast draining, fertile soil
.
    

   Light


       Light provides the energy for plants to grow. Providing adequate light levels is probably the most important factor in the long term success in growing cactus and other succulents. For the most part, succulents are adapted to conditions of bright light. The majority of species grow in exposed areas, and are adapted to grow in direct sunlight to light shade. Home interiors are much dimmer than people imagine, typically providing only about 2% to 4% of the intensity of full sunlight. Most succulents should be provided with the brightest spot available to produce their best growth. A sunny window, with a southern or western exposure is best, but an eastern exposure may be adequate for some species. If the light levels are too low, it is possible to grow some species under artificial lights. I have grown a number of species (primarily Haworthias, Gasterias and a few miniature Aloes,) under fluorescent lights and LED lights with good results. If plants are to be grown under artificial lights, the lights should be held only a few inches above the plants, otherwise the light which reaches them will be too dim to produce strong growth (I have found that incandescent lights produce too much heat to be useful for plants).

       In the spring, once temperatures rise to the 50s and 60s, I move the plants outdoors to benefit from the increased light levels, summer temperatures, and rain fall (I will speak more on the benefits of rainwater under the Water section). It is best to introduce these plants to increased light levels gradually, allowing the plants to acclimatize to increased levels of sunlight. I usually begin moving my plants to a shaded area outdoors on a cloudy day; after several days to a week, I move my plants to partial shade (again, moving them on a cloudy day); after a few days to a week, I move them to a spot in the full sun. Even succulents may be prone to scorching if they are immediately moved from interior spaces to full sunlight. Scorching will leave scars on stems and foliage; in time, new foliage will replace old foliage, but stem scarring is usually permanent. While this may mar the appearance of the plant, this is seldom fatal. Those species which are adapted to somewhat shaded situations (Haworthias, Gasterias Christmas Cactus and some of the miniature Aloes,) will probably grow best in light shade.

       When temperatures start dipping below 50 degrees in fall, I move my plants indoors.     

   Water


        While many books tout the remarkable ability of some succulents to survive extreme and extended drought (some species can survive two years or more without significant rain), only a tiny minority of cactus and succulents can survive such extreme conditions. The overwhelming majority of these plants originate from regions which are seasonally dry, but will experience a short but significant rainy season. When actively growing, most succulents will require substantial amounts of water: it is best to give them ample water (enough so that excess water flows through the drainage holes of the pot), watering the plants again only after the soil has become completely dry. Succulents should never be subjected to continually moist conditions, but during their growing season it is just as important that the plants are not subjected to an extended drought. I typically water my plants once every 7 to 14 days in summer, but much less frequently in winter (when most of these plants are dormant) - about once every 4 to 5 weeks or so.

       Summer is also a good time to fertilize succulents. I generally choose a fertilizer which can be dissolved in water and applied when the plants are watered - fertilizers such as Miracle-Gro, Peters or Dyna Gro. It is also important to choose a fertilizer with a low concentration of Nitrogen. I also try to use a fertilizer which provides the trace elements - minerals which plants require in tiny doses. The trace elements include such things as copper, iron, zinc, boron and molybdenum (to name a few). I use Dyna Gro Bloom on my plants with good results. Succulents do not generally need much fertilization, so it is recommended to mix fertilizers from 1/3 to 1/4 the recommended strength (for example, if the instructions suggest mixing one tablespoon of fertilizer to a gallon of water, mix about one teaspoon to a gallon instead). I usually fertilize my plants about once a month from mid spring through early fall, and seldom fertilize them at all through the cooler seasons.

       Water quality is another important consideration in growing succulents; well water and water from many municipal sources have significant levels of dissolved salts, and mineral compounds (calcium carbonate for example). Municipal water usually has levels of chlorine and fluorine which may also be detrimental to plants.  In potted plants, these minerals tend to accumulate in the soil, and may eventually build up to levels which are detrimental to their health (this accumulation of salts and minerals in the potting soil is probably the most important reason for periodically repotting plants). Most of the succulents will benefit when grown where they will receive summer rainfall. Rainfall can flush salts and harmful concentrations of minerals from the soil, which tend to accumulate when plants are exclusively watered with water from municipal water systems or wells. Summer rains can also assist in the control of certain harmful pests (spider mites for example), by washing them from the plants. In recent years, there has been some discussion of the importance of watering succulents with acidified water. Not only does the use of acidified water limit the accumulation of some dissolved minerals, it is also important in the uptake of key nutrients from the soil. Ideally, the water used in watering succulents should have a Ph in the range of  5 to 5.5 - if a Ph test indicates that your water has a Ph above this, adjustments can be made by adding acid to the water until the water tests within the desired range. While I have not tried this on my own plants, using an acidifying fertilizer such as Miracid may be also a good practice.    

   Heat


     Most of the succulents grow best during the summer months, when there is good light, adequate moisture, and warmer temperatures: at this time, growth can be dramatic; under ideal growing conditions, some succulents can easily double or even triple in size in a single growing season - a far cry from the popular belief that these plants are very slow growers. My plants usually produce their best growth when temperatures are warm to hot - somewhere in the range from the upper 70s to the lower 90s. It is difficult to provide these temperatures in interior spaces during the summer months, which is another reason why I choose to move my plants outdoors at this time. At typical household temperatures, cactus and other succulents will produce some growth, but will typically grow somewhat slower. Moving these plants to a warm, and sunny windowsill could provide at least a few additional degrees of heat - moving them to a sunny room without air conditioning is better still.     

      Potting, and Potting Soil


       Succulents will occasionally require repotting. Most species may only need to be repotted every 2 years or so depending upon the species and the growth rates of the plants - faster growing plants may need to be repotted more frequently - slower growing species, and virtually all species of the pebble plants and living stones (Conophytums and Lithops) may go 3, 4, or more years before they should be repotted. In clustering plants, or plants with more or less spherical or hemispherical stems, repot in a pot which is about an inch wider than the plant (tall, cylindrical plants should be potted in low but wider pots to reduce the possibility of tipping). Always use a pot or planter which has drainage hole. Virtually all succulents appreciate a very gritty soil which provides excellent drainage, good penetration of air to the roots, and which is also reasonably fertile. Most commercial potting soils are not suitable for succulent plants: they are designed to retain moisture, and usually remain wet too long to keep succulents healthy. More often than not, blends which are sold for use with cacti and other succulents are not really good for these plants: these contain too much sand, which is usually well draining, but contains virtually none of the nutrients necessary for sustained healthy growth. I have found that soils which are blended for use with bonsai are also good for use with succulents - although I suspect that it may be best to blend in a bit of regular potting soil with this to provide a bit more water retention, as bonsai soil tends to have excessively sharp drainage.

       I have had very good results growing Succulents in a potting medium containing a high percentage of Moo-Nure, a soil amendment comprised of composted forest debris and cow manure - while this may be high in organic materials, I have found its ability to dry rapidly - even after it has been thoroughly saturated with water - to be especially valuable when growing succulents. It is widely available (in Central Ohio, it is carried by all Home Depots) and it is inexpensive. Contrary to expectations, once it has had a chance to air out for a few days, it does not have an objectionable scent.    

   Dormancy     


       Most of the succulents should be given cool and dry conditions during the winter months, to keep these plants dormant. Dormant plants will usually tolerate temperatures which are quite cool, some to temperatures falling to the low 40's - but anywhere in the house which is a bit cooler than "room temperature"; window sills and Florida rooms for example, should provide adequately cool temperatures to keep the plants dormant. I move mine into a very cool basement (dormant plants do not require a lot of light, and while this works for may of my plants, there are other plants which must be provided with artificial light during the winter months) In winter, I water my plants very infrequently - about once every 4 to 5 weeks on average, but some of my larger plants are not watered at all in winter. If plants are kept at regular room temperature in winter, it may be necessary to water them slightly more often than this. Starting in spring, plants should be watered more frequently. Some species will show signs of new growth in response to the lengthening periods of daylight in spring, regardless of the frequency of watering. When plants spontaneously beak their dormancy, they should be watered more frequently, and periodic applications of fertilizer should also be started at this time.     

   Air and Air Circulation

     
       Often forgotten as a requirement for plants, atmospheric gases, particularly oxygen and carbon dioxide, are nevertheless vital. Deprive a plant of these gasses, and it will quickly perish. Carbon, extracted from carbon dioxide during the process of photosynthesis is a basic building block of all living things, and is a necessary component of all proteins, fats and sugars.

        Conditions of perpetually high humidity may impair the health of some cactus species. Humid conditions may provide environments suitable for the proliferation of molds, fungi, and bacteria as well as any number of insects pests. It is for this reason that I do not recommend growing succulents in a closed environment such as a closed terrarium - while some people can maintain succulents in a terrarium, more often than not, this is a formula for failure - if you are new to growing succulents - please resist the temptation of growing them in a terrarium - instead, consider growing them in an open dish garden.

       Good air movement can be an important factor in the health of many succulents. Moving air may help to facilitate transpiration, and may help to limit the conditions of high humidity and may prevent the proliferation of certain pathogens. If you grow your plants next to a window, consider opening the window (weather permitting) to provide good air circulation. Registers and fans can also provide good air circulation, but remember that central heating and air conditioning will quickly dry out the soil, and plants grown near registers, fans, etc., will require more frequent watering.

       Every bit as important, are the gasses which are present at the roots of a cactus. A soil which includes a high quantity of relatively large particles (coarse sand, gravel, stones, etc.) allows for the diffusion of air into the soil, and just as importantly, allows for carbon dioxide to diffuse out of the soil. Waterlogged soils do not allow for a free exchange of oxygen and carbon dioxide: in waterlogged soils, concentrations of carbon dioxide may rise to lethal levels, killing the roots. The same anaerobic conditions may create an environment suitable for the proliferation of certain soil fungi which will infect dead and dying tissues, and may ultimately kill the plant. This is usually what occurs when a plant is killed by "over-watering", the plant's roots essentially die of suffocation, and subsequently rot.

   Insect pests


       Most of the succulents are fairly disease and pest resistant, but a few pests are known to be a problem. In greenhouses and other sites where plants are grown under hot and dry conditions, spider mites can become a problem. Spider mites are tiny - smaller than the period at the end of this sentence. In large numbers, spider mites are usually revealed by their communal webs which look tike tiny spider webs. If webs are present, look carefully for the mites, which (to the unaided eye) may resemble tiny brownish-red aphids. Small infestations can sometimes be dealt with by drenching the plant with water (a stream of water will often flush these pests from the plant): this process should be repeated every few days over about a two week period.

       Mealy bugs and scale insects are pests which are difficult to eradicate once they have become a nuisance. Mealy bugs are slightly larger than the size of an aphid, and are typically of a grey to white coloration. Many individuals produce a waxy coating which may give them a whitish appearance, and some may produce such an abundance of fluffy wax that they look like tiny tufts of cotton. Mealy bugs usually occur in groups in the tight recesses of succulents, and are not always readily apparent - a few species live underground, and tap the roots of succulents, drinking the nutrient rich sap which flows in their tissues. It is therefore important to carefully inspect the roots of succulents whenever repotting. The most effective control of mealy bugs in small infestations is to seek them out and crush them - the more squeamish growers may prefer to dab these insects with a fine artists brush soaked in a solution of rubbing alcohol. There are some insecticides which may be effective against these pests, but - with the exception of Safers Soap, most of these products can be hazardous, and are not generally recommended for use in the home.

       Scale insects may look like tiny grey or brownish blisters. I tend to think of scale as an insect take on the design of the limpet; the insect hides beneath a low conical "shell", and do not look much like an insect at all. Control of scale is similar to the control of mealy bugs, but because these pests may be a bit more cryptic than mealy bugs, they may be present in huge numbers before their presence is even detected. In all cases, large infestations of any of these pests may require stronger measures - use a pesticide designed for the control of the specific pest. Not all pesticides are suitable for use on succulents - some products may cause discoloration and scorching of plants, so it is generally recommended that a test be made either on a small (replaceable) plant, or on a small portion of a larger plant. If no problems are evident after several days - it is probably safe to treat the entire plant. Always read and follow all instructions carefully - all pesticides are potentially hazardous, (including the insecticidal soaps) and all tend to be hazardous to a variety of other species, including beneficial insects, aquatic life, and birds and other wildlife. Treat all pesticides with respect.

       As a rule, healthy plants which are actively growing tend to be fairly resistant to insect infestations, so the presence of insects may possibly indicate that the plants may be weakened due to some other cause: once the pests have been dealt with, a change in growing conditions may be indicated.

   Keep in mind that these are general guidelines only: there is no single formula which will work with all succulents - you may very well have to modify these guidelines for your own plants and circumstances.

    

     Feel free to experiment, learn what works best for you and the plants in your own collection, and realize that a few mistakes will not cause the immediate demise of your plant - this is perhaps one of the best traits of succulents - they are forgiving: forgetting to water the plant one or two weeks will have no appreciable effect on the plant - you couldn't say that about most house plants. The occasional overwatering will not have a negative effect on most healthy succulents. So go ahead with confidence!

 
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