Last updated: 12 April 2018
Much of my own approach in cultivating cacti is based on that espoused by Dr. Franz Buxbaum in his book CACTUS CULTURE BASED ON BIOLOGY (translated by Vera Higgins), Blandford Press, 1958. He was a pioneer in the use of coarse inorganic growing media to insure superior drainage and root aeration -- acidifying water and soil by testing and modifying the pH -- using complete, balanced fertilizers incorporating micronutrients -- and using non-porous pots in order to maintain healthy root systems.
That is the approach I have used in growing the plants I feature on this site. Please follow your own path in cultivating the plants you grow based on their requirements, your growing environment, your climate, and the type of containers you use.
I grow all of my cacti in ubiquitous commercial plastic
pots which I believe contributes to producing healthy
and robust plants.
In addition to their light weight, a great feature of using plastic pots is the ability to easily slide established plants out of their container (and afterward slide them back in) in order to examine the condition and health of the root ball structure.
Discocactus root ball
The Soil Mix I use for these cacti
I have always experimented with soil mixes -- I think I have used about every one that has been devised during my growing lifetime -- and I have found all those that were of coarse and gritty texture, thus providing excellent drainage and root aeration, consistently produced healthy and robust plants.
In addition to producing healthy and nice looking plants, ease of plant maintenance is an important attribute of soil mixes in my opinion. They should tolerate occasional watering misadventures and be light enough to make potted plants easily transportable.The latter is of great importance for older growers, or those who are disabled to some extent, and who have difficulty walking and keeping their balance or have diminished strength in their hands and arms.
I mostly use a very porous, well aerated and reasonably light weight soil mix for cultivating the plants grown under the 30% shade cloth I use at my home -- 80% washed pumice plus 20% aged and weathered pine bark fines. I incorporate encapsulated slow release fertilizer (Osmocote) in the mix.
I don't screen out the small granular pumice fines - but I do wash out the dust using a fine sieve in conjunction with a "power spray head" garden hose as dust tends to migrate to the bottom of containers where it can form a drainage impeding "sludge".
Washing out dust using a "power spray head" garden hose and fine sieve.
The pumice described above after washing it to remove dust.
Prepared soil mix ready for use in potting plants
80% washed pumice plus 20% aged and weathered pine bark fines.
Melocactus growing in above mix
Some plants illustrated here are growing in 70% Bach's Cactus Nursery mix plus 30% raw pumice (+/- ¼"/6.35mm).
Dan Bach's Cactus Nursery
60% screened coarse and uniform (3/8"/9.53mm) horticultural pumice
20% high quality Canadian sphagnum peat moss
20% well composted shredded pine tree forest bark
I cannot perceive any difference in the quality of plants grown in either mix.
I think a high quality commercial bagged potting soil (very low in peat) mixed with a suitable proportion of ceramic (fired clay) material such as "Turface" or plain "Kitty Litter" or coarse perlite, should work pretty well.
Watering and Fertilizing
Watering: I use Tucson City tap water exclusively. I check and adjust the pH to ±6.0 using a General Hydroponics GH1514 pH Control Kit.
Fertilizing: I use a commercial 2N.7P.7K fertilizer (with micro-nutrients) at 25% strength (approx. once per week) during the growing season.
Active growing period (outdoors under 30% shade cloth): With the arrival of warm spring weather I water my plants with increasing frequency. I insure my plants receive copious amounts during the hot Arizona summer months, When I water during this time I do it from above and soak the plants until the water runs freely from the drainage holes. During our Arizona summer "Monsoon" thunderstorm season the frequent (but sporadic) heavy rains (quite acidic in the pH 5.0 to 5.5 range) reduces the hand watering requirements for my container grown plants significantly.
Because these are CAM plants (stomata opening at night) I water at early evening, often every day except for thunderstorm days, during very hot weather here in Tucson, which equates to late May until late September, when the high daytime temperatures are often in the 100°F+ (approx. 38°C+) range (often much higher) with night time temperatures dropping into the 75°F (approx. 24°C) range.
Resting period: These plants do not require a winter cold resting period in order to produce flowers the following spring (that is one reason I favor them). Winter dormancy for them results from the very dry conditions they experience during this time in their habitat. Therefor they only receive occasional light spraying or misting during this time to maintain general plant health. I use a common garden plastic spray bottle (approx. 2 quarts/1.75 liters) filled with regular Tucson tap water. I add sufficient acid solution (or distilled white vinegar) to attain a pH of approx. 6.0. From time to time, and infrequently, I add a little fertilizer in order to provide the plants with some nutrition.