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Seneca Hill Perennials
3712 Co. Rte. 57
Oswego, NY 13126
e-mail:hornig (at) oswego.edu
I am writing this from my own experience of germinating approximately 25 species of Arisaema, almost all of which seem to respond in a similar fashion to the conditions I give them. I have not conducted many experiments, and so cannot compare my methods with others. I can only report that what I do is simple, and works.
Both fresh and dry Arisaema seeds germinate easily, and at fairly high rates (75 to 100 percent). The first leaf typically appears between 4 and 8 weeks from sowing, though some species appear sooner (A. flavum ), and some will produce only a corm in the first season, with the first leaf emerging, after dormancy, in the second period of growth. In only one case have I had germination (as opposed to leaf production) delayed at length (A. limbatum, approximately 14 months). However, there are many species I have not yet tried.
I start my Arisaema seeds under standard fluorescent fixtures using inexpensive cool-white bulbs. The fixtures are on timers and are set to 14 hour days. Because the fixtures are in a cool basement, with winter temperatures typically around 13 oC, I drape and staple polyethylene sheeting over the fixtures to trap some heat (and humidity) inside. This raises the surface temperature of the pots to around 21 oC while the lights are on. I have not found it necessary to provide bottom heat.
A. Seed Preparation
If fresh seed heads or berries are available, remove the seeds from the pulp (wear latex gloves while doing this, or your fingers will burn for days) and rinse in several changes of water until the seeds are clean. They are then ready for sowing.
I find it helpful to soak dry seeds for approximately 48 hours (with several changes of water during that time) before sowing. Anecdotal evidence suggests that soaked seeds germinate 2 to 4 weeks ahead of unsoaked seeds.
B. Germination mix
The mix must be free-draining; soggy conditions promote rot. I use three parts Fafard Super- Fine Germinating Mix to one part granite chick (starter) grit. The Fafard mix contains peat moss, vermiculite, perlite, and a starter charge of fertilizer.
Although I use Kord nine cm pots for everything (because they fit neatly, 18 to a 25 cm by 51 cm tray, and I sow a lot of seeds), a deeper and narrower pot might be preferred. The nine cm pot works well as long as the mix drains freely; a deeper pot would simply promote even freer drainage.
I fill the pots and water the mix to settle it (the surface of the mix should be approximately two cm below the top of the pot). After the pots drain, the seeds are sowed on the surface of the mix and sprayed lightly with water to ensure proper contact with the mix. The surface is then covered with approximately one cm of chick (starter) grit. If I am starting large numbers of pots at the same time, I saturate the pot surfaces with a Captan spray to prevent damping-off.
I often sow 25 to 50 seeds in a nine cm pot, but that would be too many if the corms were going to be grown on in the same pot for another year. I prefer to crowd them at first and separate them later (during their first dormancy).
E. Growing On
The pots are then placed under lights, as described above, and more or less left alone, except that surface moisture should be checked every few days and replenished as necessary. It is very important that germinating seeds never dry out. I prefer surface watering, on the theory that it is less likely to saturate the bottom of the pot and create future problems.
Once leaves emerge, I fertilize from time to time with one quarter strength Miracle-Gro or equivalent. I try to keep the medium evenly moist as the leaves develop; once they are completely unfurled, they will tolerate slight drying, but excessive drying may send them into a premature dormancy.
Once the leaves are fully unfurled on all of the seedlings (and remember that seedlings may continue to emerge over a two to three week period) I remove the pots from the warm poly tents and set them under uncovered lights to grow on. I find the cooler temperatures promote more compact growth and, of course, reduce the likelihood of fungal infections.
At this point, the objective is simply to keep the leaf active and photosynthesizing for as long as possible, in order to build up as large a corm as possible before dormancy sets in.
F. First Dormancy
When the leaves on your seedlings begin to fade, yellow, and collapse, the seedlings are going dormant. At this point, cease most watering (try to keep the medium very slightly damp, but too dry is far less harmful than too wet). If you have started the seeds indoors during the winter, dormancy may well occur by early summer. Simply let the pots sit, preferably in warm and dryish conditions (i.e. in a shady outdoor location) until fall. You may find that some corms resume growth towards late summer; A. jacquemontii has a strong tendency to do this. If they do, resume watering and fertilizing and provide adequate light. Otherwise, when the weather gets cold, bring the dormant corms inside. This is a good time to empty out the pots and admire your handiwork; the corms can now be repotted (perhaps 12 to 16 to a 10 cm pot) in a more nutritious but still well-drained mix (I use Metromix 510 with perlite added, but haven't measured the proportions). As an alternative, they may be mixed with slightly damp peat moss and kept in polyethylene sandwich bags in the vegetable drawer of the refrigerator. If you choose to pot them up, water them thoroughly once and set them in a cool place (I use the coldest corner of the basement); thereafter, water only enough to prevent them from drying completely.
Corms of different species emerge from dormancy at very different times, so you should begin checking your dormant corms as early as December if they've gone dormant in June. As soon as new growth is detected, pot up (if in baggies), water, and move to a well-lit position.
I have little experience with this, but many people like to push the development of Arisaema by shifting newly-dormant corms immediately to cold conditions (the refrigerator), holding them there three months, and shifting them back to warmer conditions.
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