Cutivating small growing tropical cacti

Last updated: 11 February 2018

Equipment and Materials: Potting container of prepared substrate - small plastic pots.
Acidifier solution - Liquid fertilizer with micronutrients - pH testing solution with vial.
Garden hose power spray attachment - large sieve for washing pumice to remove dust

Introduction & Overview

Although I enjoy cultivating and displaying all arid land plants, I have a particular fondness for cacti.

Advancing years are beginning to catch up with me and I now have difficulty walking and keeping my balance, so I cultivate small growing species in containers in such a way that they will be easy to maintain and carry. This is of particular importance in following my winter maintenance regime which involves staging my plants indoors on south facing window sills at night, and during cold days, and staging them outdoors for the benefits of sunshine and fresh air during the 60°F or so (approx. 16°C) days that we frequently experience during our Tucson winters. Therefor the cacti that I cultivate here at our retirement Town Home are plants that can be maintained in 2" (5cm) and 2¾" (7cm) square plastic pots.

They are all small growing globular tropical cacti that can be easily propagated via basal offsets, or grow readily from seed, and do not requiring a cold winter rest in order to produce flowers. Such cacti are ideal for indoor winter windowsill growing.

Selected species

Frailea castanea
Habitat: typically interior dry regions of southern Brazil

Seedlings growing in 2"x2" (5cm) square plastic pots

Plants growing in 2¾" (7cm) square plastic pots

Discocactus buenekeri (sensu lato)
Habitat: typically interior dry regions of eastern Brazil

Seedlings growing in 2" (5cm) - by 3" (7.5cm) deep square plastic pots

Juvenile plant just developing a cephalium

Mature plants growing in 2¾" (7cm) square plastic pots

Flowering mature plants growing in 2¾" (7cm) square plastic pots

Discocactus horstii
Habitat: typically interior dry regions of north eastern Brazil

One of the criteria I use in selecting plants for my present collection is that they freely produce offsets, or have reasonably thin stems that provide easily rooted cuttings, thus facilitating vegetative propagation. I believe I was discussing this with K.W. during his last visit when I made the somewhat rash statement that I was getting too old and infirm to grow cacti from seed and that meant I would no longer be cultivating one of my all-time favorite species -- Discocactus horstii -- which is one of the real gems of the Cactus family Well, I couldn't stand that omission, so here is a tray of seedlings I have raised this year:

Discocactus horstii
growing in 2" (5cm) - by 3" (7.5cm) deep square plastic pots

Exemplars from my past cultivation efforts:

Uebelmannia pectinifera
Habitat: typically interior dry regions of north eastern Brazil
Seedling and mature plants in varios stages of growth

Melocactus matanzanus
Habitat: dry coastal regions of north western Cuba

Mature plant with cephalium growing in 2¾" (7cm) square plastic pot

Root system of mature plant with cephalium

Mature "rescue" plants in flower growing in
2¾" (7cm) square plastic pots

Mature plant bearing fruit in cephalium

Multi headed offsets with cephaliums resulting
from apical damage to mother plant

My general approach to Cactus cultivation

Much of my approach 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 mineral rich coarse textured 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.

The information I present here in general reflects that approach. It is important that you follow your own path in cultivating your plants based on your own physical capabilities, the requirements of the plants that you grow, your growing environment, your climate, and the type of containers you use.


I grow all of my miniature plants in 2" (6cm) or 2¾" (7cm) square plastic pots.

I became concerned that I was not providing sufficient insulation for pots against the blazing Arizona sun during the spring and summer when I stage them outdoors on the patio under 30% shade cloth. Therefor I have been experimenting with using wooden planter boxes to provide such insulation. However I still grow most of my plants without using wooden planter boxes with no apparent ill effects.

Soil mix

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.

My current primary soil mix consists of 80% Bach's Cactus Nursery mix plus 20% raw pumice (+/- ¼"/6.35mm).

Dan Bach's Cactus Nursery mix:
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

Plant growing in above mix showing root system

I think any commercial high quality bagged potting soil (very low in peat) mixed equal parts with a porous ceramic (fired clay) soil conditioner such as Turface - or coarse perlite - will work just fine.

Watering and fertilizing

Water: I use Tucson City tap water exclusively. I check and adjust the pH to ±6.0 using a General Hydroponics GH1514 pH Control Kit.

Fertilizer: I use Schultz 2N.7P.7K Cactus Formula liquid fertilizer (with micro-nutrients) at 50% strength about once per month during the growing season.

Watering Regime

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.

Spraying/Misting equipment and material

Resting period: The plants that I grow 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 7 drops of Schultz 2.7.7 liquid plant food in order to provide the plants with some nutrition.

Staging plants

During cold days, and at night during the winter months, I stage my plants in small square plastic pots within trays indoors on south facing window sills that receive full sunshine. On sunny winter days, when the temperature rises to around 60°F (approx. 16°C) -- which happens quite frequently in southern Arizona -- the trays go outdoors being staged, in full sun, on a wrought iron stand just outside my south facing bedroom window. When the temperature drops at nightfall (or sometimes during the day) I slide the window open (the screen has been removed) and retrieve the trays one at a time (they are light weight) by reaching out through the open window and positioning them inside on the windowsill.

With the arrival of spring - when the daytime temperatures climb into the 80's F (mid 20's C) and the nighttime temperatures are in the 50's F (10's C) - the plants are staged outdoors on plant stands under 30% shade cloth until the arrival once again of winter temperatures.

Summer staging under 30% shade cloth

Some small growing Brazilian cacti on plant stand - close-up photo

Link to the Cactus Cultivation Directory