The Search for the Ultimate Cycad Seed Cleaning Procedure


One of the difficult aspects with growing Zamias is the chore of cleaning the seeds. Unlike the seed coat of other cycad seeds, Zamias have a very rubbery seed coat and sticks to the seed. I have seen hundreds of thousands of seeds being wasted because people did not have the time or the method to clean them.
In my early years of growing cycads I would only produce 100 seeds or less at a time. I would watch TV at night scraping the seeds one at a time with my pocket knife. I had to find a better way than this. Next, I put the seeds in an empty pot and place that pot near a fire ant mound. Within a week the ants would pick the seeds clean. This worked pretty well but the ants wouldn't clean more than a couple of hundred seeds before they would lose interest. Dr. Bijan Dehgan, at the University of Florida, told me his favorite method was using a wire brush on a drill. He instructed me to put the seeds in a coffee can, cut a hole in the lid, and insert the wire brush into the drill through the lid so that when it was placed on the can it would keep any extra material from flying out when the drill was turned on. This worked very well but I needed something that would clean 1000s of seeds at a time. I improved on this method by taking a length of "all thread" (a metal shaft with threads all the way up and down), and placing three large wire brushes on the shaft with nuts in between each brush. I would fill an entire five gallon bucket full of seeds, add water and a little sand, and scrape the seeds for almost an hour. I would then use a pressure hose to clean off most of the residue, but not all seeds were perfectly clean. I have seen other nurserymen over the years use rock tumblers, cement mixers, and potato peelers to clean their seeds but they found that many of the seeds would be damaged. One nurseryman used to nick the seed coat, place his seeds on a bed of clean sand, cover with a screen, and pile oak leaves on everything. After a month or so the bugs and natural enzymes would clean the seeds. Even though it sounded bizarre, this was the only natural way I had ever heard of.
In 1992 an old groves man told me a story about a product he had used in the 1950's to separate the seeds from oranges so that they could be used to plant rootstock material for grafting citrus. He told me how they would throw massive amounts of oranges in a large cow trough and then cover the oranges with water. He would next pour a cup full of a liquid into the trough. In approximately a week the oranges would break down into pulp, and the seeds would sink down to the bottom of the trough. The most important aspect of this method was that the seeds were still viable. I wondered if something like this would work with cycad seeds. The man didn't even know how to read and could not give me any clues as to what this product may have been.
After months of searching (most people didn't even know what I was asking about) I discovered that product was a pectinase enzyme. From what I was told the enzyme breaks down the cellular structure of fruit but wouldn't harm other materials such as seeds or plant material. In Florida this enzyme is still used to separate the orange seeds from the fruit in mass quantities. In North Carolina it has been used to make apple juice. By using the enzyme, more juice can be produced from each apple because there is no wasted material, except for the seeds, to throw away. I thought I would check all this for myself so I procured some enzyme and conducted a few experiments. I put some Zamia floridana seeds in three different cups, and put three different strengths of enzyme solution to test for speed of cleaning. I used 1/2, 1, and 1 1/2 teaspoons of enzyme per pint of water for the three different cups. After a week, there was what appeared to be a liquid wax floating on the top, and after 2 weeks only a few seeds were clean. I assumed the enzyme was having a hard time penetrating the seed coat. I tried scraping the seed coat a little for my next experiment. Eureka! The enzyme entered the scrape and broke down the coat from underneath. Depending upon the size of the hole the seeds were perfectly clean in as soon as 5 days using the 1 1/2 teaspoon rate. All I had to do after that was to rinse them in water and I had perfectly cleaned seeds. Having to manually scrape each seeds still took too long. I found that if I soaked the seeds in a bucket for three days and then used the wire brushes for a couple of minutes, the seed coats would be damaged enough to let the enzyme work. For those who don't have a drill, I found that after the three day period, if I put some gloves on and worked the seeds through my hands for ten minutes I would get the same results.
The next question was still critical. How would the use of the enzyme affect germination? I found that even after soaking seeds for up to three weeks, I had no loss of germination. I then soaked some seeds that had recently germinated in the enzyme and after three days, the radicles weren't adversely affected. I think the key is that this is a very specific enzyme and does not work like an acid that could damage seeds.


 Uncleaned seeds

Using the brushes to loosen the seed coats

 "Seed soup"


 Rinsing off the cleaned seeds

 Cleaned seeds

After experimenting with this enzyme for years, I have found that the enzyme reacts best at 95 degrees Fahrenheit. If temperatures are lower than 80 degrees the enzyme doesn't work as well, and below 70 degrees the seed cleaning procedure may take several weeks which can rot some of the seeds. I would also like to add that once the seeds have soaked for the full time, if you use the brushes on the seeds for less than a minute, it will help dislodge any extra seed coat that may be sticking, which aids in the washing process.
I use this for most of my seed cleaning needs now. Sometimes I purchase seeds that are not totally cleaned but have found that soaking these seeds for a couple of days will clean them the rest of the way which helps keep fungus from growing on the seeds. For all you palm people out there, I have found that the enzyme will perfectly clean any of the fruity palm seeds like Arenga and Butia by just soaking them for a few days. In the case of Arengas, the seed coat is toxic and should not be handled, so this procedure is an easy way to clean these seeds without handling them. I am always testing ways to make my job easier and improve plant growth, but I think that in this case I may have the ultimate seed cleaning procedure.

New: I have had enough people asking me about this product to make some available. I have a granular form available that is very inexpensive to use. I can clean approximately 40,000 Zamia seeds with $4.00 worth of enzyme. For more information click the link.