Cycad Seed Germination
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Contents |
Introduction:
Growing a plant, especially a cycad, from a seed to maturity is a satisfying experience and usually also saves a lot in cost. Fortunately this is not really difficult to achieve with most cycads once a few basic rules are known and observed. I hope this article will serve to help you to greater success in growing cycads.
Pollination and Germination:
Once a cycad seed has been pollinated the embryo inside begins to grow and continues to do so until it is large enough to emerge from the end of the seed. External conditions do to some extent influence the process and it is necessary to provide an environment that will encourage the growth of the embryo because it is still quite small even when the seed is ripe. Some moisture is required and warmth will help but even when everything is right it may still take weeks, months, or even a year or more for germination to take place. Another complication is that some cycads (notably Encephalartos sp.) can produce seeds that are apparently perfectly formed even when no pollination has taken place. These seeds have no embryo and will never germinate! If there is reason to doubt the quality of the seeds and you have a fair number, cut one or two open and check for an embryo. Longitudinally along the centre of the seed is a hollow; inside this should be a fine coiled filament and attached to the end of that a small object which is the embryo. If the hollow inside the seed is quite empty, the seed is no good.
When you receive seeds the first step is to ensure that all flesh is removed since it may contain inhibitors and will promote the growth of fungus. Scrape the flesh away with a knife but wear protective gloves during the cleaning operation to guard against contact with slow acting poisons in the flesh. If the flesh is hard and dry it helps to soak them in water for a day or two before cleaning. Even if the seeds are clean when you get them it is a good idea to soak them for a few days preferably with daily changes of water. When the seeds are placed in water, most likely some will float. With the seeds of may species this would be an indication that the seed is of no use.
In dealing with the seeds of Cycas species, particularly Cycas circinalis and related species, this test may not apply. Inside those seeds there often is some spongy tissue which causes the seed to float even when it is perfectly good. Even seeds that attle inside their shells may still germinate. If a seed of any type of cycad floats more or less half in and half out of the water it is not likely to be any good. The soaking process may produce almost immediate germination of seeds which have been in storage and transportation for a period of three or four months (especially Dioon sp.). In this case it's very simple - a bucket of water is all that is required but it may not be wise to leave them in water for too long as some seeds will split with too much water, especially Cycas species.
The conventional method of germination is to place the cleaned seeds on their sides half buried on washed sand or potting mix, It is necessary to keep the medium moist but not too wet for as long as it takes to germinate them. An easier method is to use vermiculite. Get a plastic container with a lid (ice cream containers can be used) and fill with dry vermiculite to within about 30mm from the top. Tip half the vermiculite out into a bucket and soak in water. Drain it and then thoroughly mix with the other (dry) half. Put it into the container and place the seeds on it, partly (or completely) covered with the vermiculite. Close the lid and keep warm (preferably 25-30° C). Check weekly or fortnightly to see that the vermiculite is still moist. Blow on it- if it scatters it's dry. Use a fine mist spray to just moisten the vermiculite. Pick up a seed and look at the part in contact with the medium - it should be slightly moist.
It is easy to see when germination takes place. Seeds of Cycas species are enclosed in a cover which is made of two pieces that split apart slightly to allow the radicle to emerge. In all other species a star-shaped crack appears at one end of the seed from which the radicle grows outward. In all cycads the radicle will now begin to grow downwards to form a root. It is at this stage that I like to plant them in a container and it is wise, once germination has started, to pick out those that are ready every few days and pot them even though they have only just germinated. It can be done later but I find that each root soon forms a couple of lateral roots which are fragile and easily damaged. It may now take quite a while (weeks or months) for the radicle to split close to the seed and a leaf to emerge. By then the root system is already fairly well developed.
Seedling Care:
A good mix that is well drained should be used to plant the seedlings. It should contain about one third medium grade sand and other components can be well composted coarse sawdust or very fine pinebark. Ingredients which decompose fairly rapidly, and let the mix become soggy, should not be used. (Air filled porosity of the mix should be about 20%). Containers used for potting should be as tall as possible. To save room several seedlings may be put in a 200mm or 250mm planter but of course great care must be taken when separating them later for individual planting. Small roots are very fragile and planting in individual containers is to be preferred. Slow release fertilizer may be used together with occasional watering with liquid fertilizer containing trace elements, particularly chelated iron. Some slow release fertilizers already contain extra iron and trace elements so the liquid feed may not be required. Most cycads can be watered quite freely so long as the mix drains very well. With good cultivation practices growth can be reasonably rapid and the results very rewarding.
Will Kraa (from Palms & Cycads No. 25, Oct-Dec 1989).
Another View:
Use community pots for sprouted seeds which are at least 12" deep. This promotes strong tap root development and conserves valuable space. After 1-2 years or longer seedlings can be removed and put into individual containers. Put l" of gravel at the bottom of your pot for extra drainage and 1" of coarse river sand on the top of the potting mix to prevent the potting mix from drying out too fast.
Give the cycad seedlings more water rather than less water so that they never dry out. To prevent root rot make sure that the potting mix is very open and exceptionally well drained. This will allow more air around the roots and promote faster root development.
Fertilise the cycads with slow release osmocote or nutricote (some growers say this is not as good). I use a 6-9 months formula with trace elements added. I also water with naturakelp or a fish/seaweed concentrate about every 6 weeks.
I germinate my cycad seed in cliptop plastic bags in slightly damp perlite and vermiculite soaked in fungitide (previcure) in a cool place. This keeps pests out and avoids the temptation to to force the seed into early germination which never works and usually spoils the seed. After the seed is germinated I put the seed on a hot bed until the root is 1-2" long and then into the pot. This minimises losses which can occur if the seed dries out before the root is long enough.
Planting cycad seed too early often ruins the seed especially if it is planted in hot or wet conditions, or it dries out before it is ready to germinate. Strong fresh seed in plastic bags in cool dry conditions for 2-6 months is recommended. To determine when the seed is ready to germinate a few can be planted or placed in damp vermiculite in another bag. Or if numbers permit one can be cut open to observe the development of the embryo. From my experience very few varieties of cycad seed are ready to germinate after they come off the plant. The most common mistake I have made is keeping the seed too damp and planting the seed too early. If your seed start to dry out (check every 2 weeks for rattlers) soak the seed again to rehydrate it, then dry it and store it again until it is time to plant.
Peter Heibloem
Germinating Seeds:
My preferred method is to put them in a mixture of vermiculite/peat moss/perlite (3:2:1) mix, and then water to the point where if you squeeze it hard no water comes out. Put this into a large polystyrene vegetable box, and place the seeds approximately as deep as they are wide for palms, or just press them half way in for cycads i.e. half submerged in the mix.
With the lid on the boxes you can store them on top of each other. Try to keep them at about 25 degrees C, and regularly check on the moisture. You most likely will have to water at about two weeks to cater for absorption, and then regularly after that. Don't forget to soak the seeds prior to sowing; for most small, soft seeds l day should be enough.
Don't forget to label your seeds, especially if you have more than one species in the box. I sometimes cut up a plastic milk carton into shallow rings, place them in the mix, and sow the seeds inside. The area is usually large enough for a several small seeds.
The above method is suitable for the majority of seeds and this should give you a reasonable strike rate, 60% to 80% is considered normal. To expect 100% germination is unreasonable, although it sometimes happens.
Rudy Meyer
