The choice of material that comprises your growing media will
probably be the most important decision you can make in growing
a superior cycad. Proper fertilizer is important, but a poor growing
medium can render even the best fertilizers virtually useless.
Organic materials that are commonly used to make up potting soil in Florida are: Florida peat, Canadian peat, pine bark, and saw dust. To increase drainage, people use very coarse sand, chicken grit, pumice, Perlite, Airlite, Zonolite, and other similar products.
One thing that many people fail to realize is that most everything involved with growing plants breaks down to chemistry and physics. When choosing a component for your soil, not only do you look at what the material is now, but what it will become later. Florida peat will very quickly turn into muck. Growing cycads in muck is probably the worst thing you can do. PH is also very important. Pine bark as it breaks down will turn your soil very acidic. The chemistry between your soil and fertilizer breaks down with very high or very low pH.
Pine bark, if not aged for a sufficient amount of time, can leach out as much as 50% of the nitrogen in your fertilizer. It also seems to be a magnet for ants, cockroaches, and termites.
Florida peat is made of organic materials that have broken down over many, many years. All the trees, bushes, and other small plants in a certain area die, then break down and settle in a depressed area. After thousands of years, this becomes a peat bog. Any nursery person can tell you that most plants are susceptible to their own particular insects and pathogens. Peat derived from several species of plants may also be susceptible to just as many pathogens as the plants themselves. Canadian peat is primarily broken down sphagnum moss. Not only does Canadian peat not break down as fast as Florida peat, but it also does not seem to be as susceptible to disease.
I originally used a standard nursery mix of 50% Florida peat and 50% aged pine bark. Then I would add coarse sand to that mix. Depending on the cycad species I was potting up at that time, I would add sand so that it made up 20% to 50% of the total mix. Central American Zamia would get 20% sand, whereas Encephalartos horridus or E. arenarius would need 50% sand. After that, I would add about 10% to 20% Perlite. Even though that all worked very well, I was having problems from time to time with fungus, especially with seedlings. Also, not having a uniform mix caused problems with watering. Some of the plants were getting dry too fast, and some were staying too moist.
One day I went to Kurt Decker's nursery and looked at his soil mix. It was made up of 40% Canadian peat, 30% coarse sand, 20% cypress saw dust, and 10% Perlite. After seeing seedlings that we had purchased at the same time, and realizing that his were larger than mine, I thought I would try his mix. After using this mix for three years, I have seen great results. The plants root faster, I have not had as many problems with pathogens, and it is a uniform mix I can use for everything. Also, because it is Canadian peat based, it breaks down slower, and I don't have to re-pot as often.
My problem was that my original soil mix cost about $14.00 per yard, whereas the new mix is about $32.00 per yard. The former owner of 1-4 Plantland, Don Maynard, used to tell me, "The most expensive thing you can buy is cheap soil." To illustrate this point, he explained that he had purchased two loads of "bad soil". After about a year, he threw away $75,000.00 worth of azaleas. For those of you who say you can't afford $32.00 per yard, let's look at this monetarily. The difference between the two soils in cost is $18.00 per yard. Most people can fill 250, one gallon pots per yard. If you are growing rare species of Zamia, even if you lose only one plant out of 250 because of cheap soil, which is the better choice? I would also venture to say you would lose a lot more than just one plant, on the average. Losing ten plants could pay for a ten yard load of good soil.
Through the years, I have always had problems with the "parazamia" type of Macrozamia. For the last four years, I have been growing Macrozamia in pure coarse sand, with a small amount of regular soil in the bottom of the pot. If you just use sand, it will pour out the bottom of the pot when it gets dry. Since I have been doing this, I have not lost even one Macrozamia. It is important, however, that you use a complete fertilizer like Nutricote, because sand obviously has no nutrients.
Along with fertilizer, the type of soil is the most important variable for growing a healthy cycad. The only other variable is water, but that is a subject for another article. When the chemistry between your fertilizer and the soil is working well, you can then use advanced nursery techniques to manipulate your cycads to grow faster, and to produce more seeds, as well as reduce your plant mortality rate.