Fertilizers can be the most important "tool" for manipulating your cycads to perform the way you want them to. First you have to ask yourself, what am I trying to accomplish by using a particular fertilizer? A homeowner-collector may want the healthiest plants possible, in the easiest possible way. A lot of times people don't have enough time to fertilize all their plants several times a year. A nurseryman wants to grow the fastest plant possible. The faster the finished product, the better the turnover, and the more money you make. Companies like Disney, that are concerned more about display purposes, want their plants to look good. With our frosts and freezes, Cycas revoluta can get spotted and burned. By forcing leaves out earlier, the waiting time for new leaves can be minimized. The person who is interested in producing seeds wants a plant to grow as fast as possible until it cones. After that point, a female bearing seeds needs to be strong enough to take the strain of holding seeds (usually for a year). Also, I have found that a strong, healthy plant produces more seed than a weak plant. As an example, I have a Ceratozamia kuesteriana that produced 188 seeds. The next year, in a weakened state, it produced 97 seed. After fertilizing the plant and waiting a year, it produced 270 seeds. After experimenting for several years I have found a way to "force" cones on cycads. The first year I succeeded, I doubled, and tripled my seed production, depending on the species. For the last three years, my seed production has continued at this level, or increased on multi-headed cycads.
People are just finding out how energy oriented cycads really are. In habitat, many cycads push leaves, at most, once a year. Plants that are hundreds of years old, in many cases, only produce female cones every five to eight years. Most species of cycads can cone every year, and produce multiple leaf flushes each year, with the proper energy. Cycas taitungensis in particular, can produce leaves up to six times a year. I find many people using palm fertilizer on cycads. They think because cycads look like palms, they are closely related. Of the seed bearing plants, cycads are about the farthest plant group away from palms. Most palm fertilizers are low in nitrogen (with N around 7-10). To produce a high enough energy level so that previously mentioned results can be attained a fertilizer with a nitrogen level around 18-25 needs to be used.
After documenting leaf flushes on 150 species and coning cycles from 25 species and correlating these results with fertilizer applications from eight brands of fertilizer, I am pleased with two brands. The first is Scott's Premix with Minors. It is a 24-7-8 plus minors, with 14 of the 24% being derived from a fast reacting nitrogen. The second is Nutricote 360. It is an 18-6-8 with minors, 360 day formula. According to the distributors, the pellets are plastic coated, and do not release more fertilizer when watering is increased. The Premix gives a big push in the beginning, but levels off. It lasts about three months, so it is used in cycles, four times a year. Nutricote starts out slow, but after 6-9 weeks, stays at a constant level for up to 10 more months, depending on the temperature of the growing area.
In the beginning stages of growth, usually only one leaf is pushed at a time. With each consecutive leaf flush, the number of leaves per flush increases. In these beginning stages, it is common for leaves to push several times a year. At a certain point, when larger, cycads seem to change the way they grow and only flush once per year, but many leaves per flush. As the number of leaves per flush increases, the higher the energy level necessary to force these new leaves out.
In the beginning stages, the Nutricote wins hands down for the fastest, healthiest plants, When the plants get larger (around the six leaf per flush stage), the Premix works better. As an example, I have a group of eight Encephalartos ferox that produce 3-4 flushes per year using Premix. When I switched to Nutricote, they flushed once during the entire year. The next year, I went back to Premix and got 3-4 flushes on all eight plants. According to an article written by Hannes Robbertse in The Journal of the South African Cycad Society, cycads have an episodic growth pattern. In most cases, I have found this to be true. Palms have more of a continuous growth pattern. For this reason alone, your strategy for growing cycads needs to be different from growing palms. My Macrozamia and Stangeria seem to have a continuous growth pattern. For these two genus, Nutricote works better.
After plants get burned in the wintertime, apply Premix at the highest level on the label instructions. After that, wait two weeks and cut off all the burned leaves. Usually within three weeks, new leaves will be produced. I have used this procedure in the middle of winter, and produced leaves on Zamia furfuracea, Cycas revoluta, and C taitungensis. If you use this procedure in the wintertime, and expect a frost before the leaves harden, application of a copper based fungicide to the new leaves when they are full size will harden them in a fraction of the normal time.
A problem with some (usually central American) Zamias is that they can grow too fast, and the caudex will split right down the middle. They usually harden up, but sometimes they die. Not only did all the Zamias react well to Nutricote, producing many flushes per year, I have not had a single plant split in years. With premix, I had 3 or 4 plants splitting every year. They really seem to like the constant feed. It is important to note that some people have found that increasing or decreasing watering schedules has caused splitting of Zamias.
If you are looking to produce seeds, first you have to grow a cycad to the size that it can tolerate the strain of holding seed. Most cycads have a starch content of about 65%. This starch reserve is somewhat depleted while holding seed. To stimulate cone production, the plant needs to feet strong enough to hold seeds. If you fertilize with Premix two months before the expected emergence of cones, the plant will have this extra strength. Once you have produced cones, switch to Nutricote, and this will keep the plant healthy for the rest of the year. Each species has its own timing for producing cones. If you don't know when to expect cone formation, you may have to watch your plants the first year and chart their timing. Either that or ask someone in your area who has dealt with that species before.
Some species react well to fertilizer applications, some do not. The plants that react best, at least in my collection, are Cycas taitungensis, C revoluta, Encephalartos arenarius, and E. ferox. You will see the best results of the use of Premix with these species. Dioon mejiae does not react well to fertilizer. This species seems to wait until about June or July when the weather heats up before leaves are produced. For plants like this, you may as well use Nutricote because it's easier.
A homeowner may not have enough time to fertilize often. In many cases, a homeowner may want nice looking plants, but may not care how fast the plants grow. In this case, they can use Nutricote. One application in the spring and forget about fertilizing for the rest of the year.
Fertilizers can be the most important tool a grower can use. Keep in mind that over-use or over application of fertilizers can kill your plants. As long as the pH of your soil does not incapacitate your fertilizer, the proper use of it will show you great results. Cycads are thought to be very slow growing plants. In habitat, these plants are relying on their coralloid root systems, which produce very low levels of nitrogen. If you use a high nitrogen fertilizer that has a release pattern similar to the growth pattern of a particular species, growth can be optimized. With the proper use of fertilizers, cycads may no longer need to be known as "slow-growing" plants.
This article is mainly to explain how cycads react to certain fertilizer applications. It is not important to use these particular products, but a produce that has the same basic analysis. Premix in particular, has been discontinued. Also, certain products may not be available in different parts of the world. For those people in Florida who may be interested, I have had a wholesale fertilizer company produce a fertilizer to my exact specifications. It has been tested by myself and and others in different parts of the US, and it has been working very well. I have improved it over the old mix. I have it available now in 50 pound bags.