Introduction
Growing and propagating cacti is relatively easy to do and can be quite
rewarding. For the most part there are three environmental variables to consider
to ensure your experience with growing cacti is successful. These are:
We'll examine these three conditions in greater detail shortly, but first let's
note that there are at least two different groups of cacti. There are the desert
cacti which is certainly the first type to come to mind whenever someone hears
the word "cactus". However, there are also jungle cacti which grow in
rain forests and other environments that most would consider the least likely
habitat for a cactus plant. I'll address growing conditions for the two separately
beginning with the jungle cacti.
Jungle Cacti
Jungle cacti include those species in genera such as Acanthocereus,
Disocactus, Epiphyllum,
Hatiora, Hylocereus,
Lepismium, Rhipsalis,
Schlumbergera, Selenicereus,
and perhaps a few others. Almost everyone has seen at least one representative
from this group even if they were unaware that the plant was actually a cactus.
The most common of these are the holiday cacti, Easter Cactus- Hatiora
gaertneri, Thanksgiving Cactus- Schlumbergera truncata and
Christmas Cactus- Schlumbergera x buckleyi. These plants are all true
cacti despite their lack of big spines and inability to withstand the harsh
conditions of the desert. (Visit the Cacti or Not? page to learn more about what
qualifies a plant as a cactus.) Now when we associate "cactus"
with one of these, it does not seem unusual that they would require different
care when growing than the stereotypical image that comes to mind when we
think about the family cactaceae.
Soil
Most Jungle cacti are either epiphytic or lithophytic meaning they grow in trees or
grow on rocks respectively. This type of plant gets its nutrients from the air
or from dead leaves and other debris that may have collected in crotches, cracks, or
crevasses. It is important to note that there are no parasitic cacti. Those that grow
in trees do so for support, but do not sap nutrients from their host. For best results
we'll want our soil to mimic these natural conditions.
Some good ingredients for creating a suitable potting mixture for Jungle Cacti include:
orchid bark, pearlite, potting soil, peat, coir, pumice, and oak leaf mold. I haven't
tried all of these, but have found a mix that works really well for my plants. I start
with some coarse orchid bark (about 25%), mix in some potting soil (25%), peat (25%),
and the rest mostly pearlite with maybe 5% coarse gravel. I've heard enough people
suggest that coir is a superior substitute for peat and have recently experimented with it, but
have not used it long enough to tell if it actually works better. The most
important aspect of the mixture is good drainage. The pearlite helps create this by
keeping the soil loose and "airy" and so does the orchid bark. Additionally the
orchid bark tends to hold more moisture than pearlite or gravel. Pumice can be substituted for
the pearlite. Keep in mind that the orchid bark will eventually break down into soil. This will
create a very rich soil that may not be as effective in keeping the roots healthy. It isn't a bad
idea to re-pot these plants every 2 or three years with a fresh mix. The best time to do this is
shortly after your plant has finished blooming. This is when it will be ready to start growing again.
You might also add some fertilizer to the new mix such as bone-meal and/or Osmocote.
For more information on creating a soil mix see
this article.
Water
It is no accident that I've listed water as the second item on the list. This is because
a well drained soil is critical for keeping the water from rotting the roots off the plant.
With the proper soil, however, watering is really quite simple. I water my Jungle Cacti about
once a week. This is a good rule of thumb, but there are exceptions. During extended hot,
dry periods I may water twice in one week. Conversely, when it is cool and rainy I might
switch to every other week. I grow all my cacti outdoors which is a privilege afforded by my
Southern California location. Indoor plants should have less variation in watering needs.
For those living in colder regions, you may find that you have to water your indoor
Jungle Cactus more in the winter than in the summer due to the dryer air from running
the heater.
The easiest way to gauge whether or not it's time to water is to stick your finger in
the top 1/2 inch of soil. If the soil is dry, go ahead and water. If it's not, wait!
Don't let your Jungle Cactus go too long without water. If the stem segments are shriveled
and the soil is dry, it is probably in need of water. Be careful! If the plant is
over watered, the stems will also look shriveled, but the soil will be damp. If this is the
case, do not give it more water. An over-watered plant will start to turn yellowish, then
get more and more mushy and dark reddish-brown like a rotten apple. This is because the cells
took in so much water they broke and are now dead and rotting. This usually happens from the
ends first. This will continue even after you stop watering too much, but often you will have enough plant
left to start over.
Light
Jungle Cacti can survive in a wide range of light conditions. However, we'll assume the
goal is not to have plants simply surviving, but thriving. For the plants to thrive the
amount and intensity of light are key ingredients. In my experience the ideal condition
for Jungle Cacti is full morning sun and then shade for the afternoon. All the plants I
have in this ideal condition exhibit robust and healthy growth.
There are three other lighting situations that are not as ideal, but often times necessary
due to space constraints. These are morning shade/full afternoon sun, full shade, and full
sun. Let's explore these conditions further. It may seem that shade in the morning and full-sun
in the afternoon should produce the same results as full morning sun/afternoon shade, but
it doesn't. This is because the temperature is cooler in the morning than the afternoon
and for many plants the afternoon sun is a little too intense and plants will often
take on a sickly-yellow appearance and may develop spots. In full-sun these symptoms
will be even more apparent. As with most things in nature there are exceptions and some plants
actually prefer full-sun and thrive in it. In full shade the plants will don a dark-green
healthy appearance, but the stems will be stretched out long and thin in an attempt to reach
more light.
Not only is light essential for healthy stems, it also triggers blooming in many species.
In ideal conditions a particular plant may exhibit fantastic growth with many show-quality
stems, but they won't bloom. In this situation exposing the plant to longer and more intense
sunlight will trigger it to bloom. Don't forget that plants can get sunburn just like
people do. If you have a plant that has been mostly shaded, don't just stick it out
in direct sunlight or you will certainly end up with a badly scared cactus. This is even true
for desert cacti that occur naturally in extremely hot, intense sunlight.
Desert Cacti
Desert cacti hail from throughout the arid regions of the America's and surrounding
islands. There are no desert cacti native to the old world and only one jungle species
that occurs in Madagascar.
Despite this, many people envision cacti growing in pure Sahara Desert sands with practically no
water. This common mis-perception should not be in your mind when you are preparing an environment
for your desert cacti.
We'll explore the requirements for growing healthy desert cacti shortly. First let's summarize
the different types of desert cacti you may encounter. There are small rounded, flat, or
cylindrical plants; there are shrubby, segmented, and sprawling kind; and there are the
large columnar and tree-like giants. Although even within each of these groups growing conditions
vary from one plant to another, I'll generalize as much as possible for a successful
all around growing environment.
Soil
The perception I mentioned earlier of cacti growing in pure sand is not held by any
successful cacti grower. Most cacti prefer a nutrient rich, rocky soil with good drainage.
To create a suitable growing median for our desert cacti we'll use some of the same ingredients
that we used for jungle cacti as well as some new ones. These are pearlite, pumice, potting soil,
rocks, sand, peat, coir, and gravel. After trial and error and advice from other growers, I have
settled on an easy, well-draining mix. This mix consists of 60% pumice, 20% coir, 20% Supersoil (topsoil).
The pumice can be replaced with pearlite or vermiculite and the coir replaced with peat. I would recommend
using only 10% peat, not 20% if you don't use coir and make up the difference with more supersoil, pumice,
or even sand. This is because peat tends to be rather hard to re-wet and can make your mix impenetrable to
water. For larger pots or mixes directly in the ground I like to add 1 to 2 inch lava rocks from anywhere
between 5 and 10 percent. I've had great success with this, but it can make digging or transplanting more
difficult because you'll hit rocks with your trowel or shovel. Some people use earthworm castings for extra
nutrients. I've always mixed in some Osmocote time-release fertilizer and have also mixed bone-meal
in some of the time.
Remember, there is no one mix that is the perfect mix. Ultimately, you'll want to experiment
with different ingredients until you find one that works for you. Just remember that cacti
roots need a well-draining, airy soil that will re-wets easily. Use whatever materials are most
readily available to you locally. A simple observation to determine if your mix
is cacti-suitable can be made each time you water. The water should not sit on top of the surface and
eventually drain down through the mix. Instead the water should very quickly soak down through the pot
and out the drain holes at the bottom. Always make sure that your pots have good drainage holes and that
no water is able to sit in the bottom of the pot.
For more information on creating a soil mix see
this article.
Water
Their ability to survive in extremely hot, arid, harsh habitat is a truly fantastic attribute
of cacti. However the notion that cacti do not need water or that they actually must avoid water
in order to survive is unquestionably false. The reality is water is essential for all cacti to
live. Their reputation comes from their ability to survive in areas where water is available in
small amounts or is delivered infrequently. Most desert cacti can sustain long periods of drought. This is because
the last time water was available to them, they stored as much as possible in their tissues. Additionally
cacti contain many features that enable them to keep that moisture and not dry up in the heat of
their environment.
Desert cacti are made to thrive in their native environment, which is most likely not anything like
the environment where you'll be growing them. Even so, when it comes to watering cacti, there is
no reason to artificially create drought. Whether potted or in the ground, a good time to water
desert cacti is whenever the soil is dry. In hot, dry areas such as Souther California in summer, watering
once a week is acceptable. In more humid or cooler areas, it may be three to four weeks before
the soil dries enough to warrant more water. The key then isn't to avoid watering, but rather just don't
over-water. With that said, it is still better to under-water than to over-water. Avoid watering if the
soil is still moist. There are exceptions to every rule and just like choosing the right soil, you'll need
to experiment to find the best watering regime for your plants.
Light
Unlike the jungle cacti, desert cacti typically prefer a lot more light. My desert cacti, which are
planted right in the ground, get full sun all day long and love it. My potted plants, seedlings, and
newly rooted cuttings only get sun for half a day. The sun would make short work of plants that
are not established. Therefore it is not wise to move cacti into the full sun until they have
a healthy root-system. Even if potted plants are established, full sun should be avoided. This is
because the sun will heat the roots in pots to temperatures much higher than roots in the ground.
This is not a natural condition and the roots are not made to survive high temperatures so make
sure your potted plants don't get too hot. One way to prevent this is by using white pots instead of black.
If you are growing your potted plants indoors, it will be highly unlikely that you'll find a spot
where your cactus gets too much light. If anything, the opposite will be true. In the case of limited
natural light, full-spectrum fluorescent lights can be used to supplement or replace sunlight. You
can get approximately 24 square feet of growing space under four 74-watt tubes for a cost that is under
fifty dollars. It will be easy to tell if your cacti need more light. Cacti that are not getting
enough light will exhibit thin, stretched-out growth. If you are unsure what normal growth is
supposed to look like, look for pictures of your plant on CactiGuide.com or other sources.
Conclusion
Growing cacti can be a lot of fun and doesn't require tremendous effort. Creating the growing
environment that works best for you will likely require some trial and error. Once you
establish the best soil, water, and light mix for your location the cacti will do the rest.
Cacti come in a diverse range of unique and/or unusual growth forms. I have gotten a
lot of enjoyment out of both growing cacti and building CactiGuide.com.
I hope that this information helps others likewise find enjoyment in the hobby.
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